rfc8941.form.xml   rfc8941.xml 
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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft
<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" -ietf-httpbis-header-structure-19" number="8941" submissionType="IETF" category=
docName="draft-ietf-httpbis-header-structure-19" number="0000" "std" consensus="true" obsoletes="" updates="" xml:lang="en" tocInclude="true" s
submissionType="IETF" category="std" consensus="true" obsoletes="" ortRefs="true" symRefs="true" tocDepth="3" version="3">
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tocDepth="3" version="3">
<!-- xml2rfc v2v3 conversion 2.46.0 --> <!-- xml2rfc v2v3 conversion 2.46.0 -->
<front> <front>
<title>Structured Field Values for HTTP</title> <title>Structured Field Values for HTTP</title>
<seriesInfo name="RFC" value="0000"/> <seriesInfo name="RFC" value="8941"/>
<author initials="M." surname="Nottingham" fullname="Mark Nottingham"> <author initials="M." surname="Nottingham" fullname="Mark Nottingham">
<organization>Fastly</organization> <organization>Fastly</organization>
<address> <address>
<email>mnot@mnot.net</email> <email>mnot@mnot.net</email>
<uri>https://www.mnot.net/</uri> <uri>https://www.mnot.net/</uri>
</address> </address>
</author> </author>
<author initials="P-H." surname="Kamp" fullname="Poul-Henning Kamp"> <author initials="P-H." surname="Kamp" fullname="Poul-Henning Kamp">
<organization>The Varnish Cache Project</organization> <organization>The Varnish Cache Project</organization>
<address> <address>
<email>phk@varnish-cache.org</email> <email>phk@varnish-cache.org</email>
</address> </address>
</author> </author>
<date year="2020" month="July" /> <date month="October" year="2020"/>
<area>Applications and Real-Time</area> <area>Applications and Real-Time</area>
<workgroup>HTTP</workgroup> <workgroup>HTTP</workgroup>
<!-- [rfced] Please insert any keywords (beyond those that appear in
the title) for use on https://www.rfc-editor.org/search. -->
<keyword>example</keyword>
<abstract> <abstract>
<t>This document describes a set of data types and associated algorithms <t>This document describes a set of data types and associated algorithms
that are intended to make it easier and safer to define and handle HTTP that are intended to make it easier and safer to define and handle HTTP
header and trailer fields, known as "Structured Fields", "Structured header and trailer fields, known as "Structured Fields", "Structured
Headers", or "Structured Trailers". It is intended for use by Headers", or "Structured Trailers". It is intended for use by
specifications of new HTTP fields that wish to use a common syntax that specifications of new HTTP fields that wish to use a common syntax that
is more restrictive than traditional HTTP field values.</t> is more restrictive than traditional HTTP field values.</t>
</abstract> </abstract>
<note>
<name>Note to Readers</name>
<t><em>RFC EDITOR: please remove this section before publication</em></t>
<t>Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at <eref
target="https://lists.w3.org/Archives/Public/ietf-http-wg/">https://lists.
w3.org/Archives/Public/ietf-http-wg/</eref>.</t>
<t>Working Group information can be found at <eref
target="https://httpwg.github.io/">https://httpwg.github.io/</eref>;
source code and issues list for this draft can be found at <eref
target="https://github.com/httpwg/http-extensions/labels/header-structure"
>https://github.com/httpwg/http-extensions/labels/header-structure</eref>.</t>
<t>Tests for implementations are collected at <eref
target="https://github.com/httpwg/structured-field-tests">https://github.c
om/httpwg/structured-field-tests</eref>.</t>
<t>Implementations are tracked at <eref
target="https://github.com/httpwg/wiki/wiki/Structured-Headers">https://gi
thub.com/httpwg/wiki/wiki/Structured-Headers</eref>.</t>
</note>
</front> </front>
<middle> <middle>
<section anchor="introduction" numbered="true" toc="default"> <section anchor="introduction">
<name>Introduction</name> <name>Introduction</name>
<t>Specifying the syntax of new HTTP header (and trailer) fields is an <t>Specifying the syntax of new HTTP header (and trailer) fields is an
onerous task; even with the guidance in <xref target="RFC7231" onerous task; even with the guidance in <xref target="RFC7231" section="8.
sectionFormat="of" section="8.3.1"/>, there are many decisions - and 3.1"/>, there are many decisions -- and
pitfalls - for a prospective HTTP field author.</t> pitfalls -- for a prospective HTTP field author.</t>
<t>Once a field is defined, bespoke parsers and serializers often need <t>Once a field is defined, bespoke parsers and serializers often need
to be written, because each field value has slightly different handling to be written, because each field value has a slightly different handling
of what looks like common syntax.</t> of what looks like common syntax.</t>
<t>This document introduces a set of common data structures for use in <t>This document introduces a set of common data structures for use in
definitions of new HTTP field values to address these problems. In definitions of new HTTP field values to address these problems. In
particular, it defines a generic, abstract model for them, along with a particular, it defines a generic, abstract model for them, along with a
concrete serialization for expressing that model in HTTP <xref concrete serialization for expressing that model in HTTP <xref target="RFC
target="RFC7230" format="default"/> header and trailer fields.</t> 7230"/> header and trailer fields.</t>
<t>A HTTP field that is defined as a "Structured Header" or "Structured <t>An HTTP field that is defined as a "Structured Header" or "Structured
Trailer" (if the field can be either, it is a "Structured Field") uses Trailer" (if the field can be either, it is a "Structured Field") uses
the types defined in this specification to define its syntax and basic the types defined in this specification to define its syntax and basic
handling rules, thereby simplifying both its definition by specification handling rules, thereby simplifying both its definition by specification
writers and handling by implementations.</t> writers and handling by implementations.</t>
<t>Additionally, future versions of HTTP can define alternative <t>Additionally, future versions of HTTP can define alternative
serializations of the abstract model of these structures, allowing serializations of the abstract model of these structures, allowing
fields that use that model to be transmitted more efficiently without fields that use that model to be transmitted more efficiently without
being redefined.</t> being redefined.</t>
<t>Note that it is not a goal of this document to redefine the syntax of <t>Note that it is not a goal of this document to redefine the syntax of
existing HTTP fields; the mechanisms described herein are only intended existing HTTP fields; the mechanisms described herein are only intended
to be used with fields that explicitly opt into them.</t> to be used with fields that explicitly opt into them.</t>
<t><xref target="specify" format="default"/> describes how to specify a <t><xref target="specify"/> describes how to specify a
Structured Field.</t> Structured Field.</t>
<t><xref target="types" format="default"/> defines a number of abstract <t><xref target="types"/> defines a number of abstract
data types that can be used in Structured Fields.</t> data types that can be used in Structured Fields.</t>
<t>Those abstract types can be serialized into and parsed from HTTP <t>Those abstract types can be serialized into and parsed from HTTP
field values using the algorithms described in <xref target="text" field values using the algorithms described in <xref target="text"/>.</t>
format="default"/>.</t> <section anchor="strict">
<section anchor="strict" numbered="true" toc="default">
<name>Intentionally Strict Processing</name> <name>Intentionally Strict Processing</name>
<t>This specification intentionally defines strict parsing and <t>This specification intentionally defines strict parsing and
serialization behaviors using step-by-step algorithms; the only error serialization behaviors using step-by-step algorithms; the only error
handling defined is to fail the operation altogether.</t> handling defined is to fail the operation altogether.</t>
<t>It is designed to encourage faithful implementation and therefore <t>It is designed to encourage faithful implementation and therefore
good interoperability. Therefore, an implementation that tried to be good interoperability. Therefore, an implementation that tried to be
helpful by being more tolerant of input would make interoperability helpful by being more tolerant of input would make interoperability
worse, since that would create pressure on other implementations to worse, since that would create pressure on other implementations to
implement similar (but likely subtly different) workarounds.</t> implement similar (but likely subtly different) workarounds.</t>
<t>In other words, strict processing is an intentional feature of this <t>In other words, strict processing is an intentional feature of this
specification; it allows non-conformant input to be discovered and specification; it allows non-conformant input to be discovered and
corrected by the producer early, and avoids both interoperability and corrected by the producer early and avoids both interoperability and
security issues that might otherwise result.</t> security issues that might otherwise result.</t>
<t>Note that as a result of this strictness, if a field is appended to <t>Note that as a result of this strictness, if a field is appended to
by multiple parties (e.g., intermediaries, or different components in by multiple parties (e.g., intermediaries or different components in
the sender), an error in one party's value is likely to cause the the sender), an error in one party's value is likely to cause the
entire field value to fail parsing.</t> entire field value to fail parsing.</t>
</section> </section>
<section anchor="notational-conventions" numbered="true" toc="default"> <section anchor="notational-conventions">
<name>Notational Conventions</name> <name>Notational Conventions</name>
<t> <t>
The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
"<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
"<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are
to be interpreted as to be interpreted as
described in BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/> described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/>
when, and only when, they appear in all capitals, as shown here. when, and only when, they appear in all capitals, as shown here.
</t> </t>
<t>This document uses algorithms to specify parsing and serialization <t>This document uses algorithms to specify parsing and serialization
behaviors, and the Augmented Backus-Naur Form (ABNF) notation of <xref behaviors and the Augmented Backus-Naur Form (ABNF) notation of <xref tar
target="RFC5234" format="default"/> to illustrate expected syntax in get="RFC5234"/> to illustrate expected syntax in
HTTP header fields. In doing so, it uses the VCHAR, SP, DIGIT, ALPHA HTTP header fields. In doing so, it uses the VCHAR, SP, DIGIT, ALPHA,
and DQUOTE rules from <xref target="RFC5234" format="default"/>. It and DQUOTE rules from <xref target="RFC5234"/>. It
also includes the tchar and OWS rules from <xref target="RFC7230" also includes the tchar and OWS rules from <xref target="RFC7230"/>.</t>
format="default"/>.</t>
<t>When parsing from HTTP fields, implementations <bcp14>MUST</bcp14> ha ve behavior <t>When parsing from HTTP fields, implementations <bcp14>MUST</bcp14> ha ve behavior
that is indistinguishable from following the algorithms. If there is that is indistinguishable from following the algorithms. If there is
disagreement between the parsing algorithms and ABNF, the specified disagreement between the parsing algorithms and ABNF, the specified
algorithms take precedence.</t> algorithms take precedence.</t>
<t>For serialization to HTTP fields, the ABNF illustrates their <t>For serialization to HTTP fields, the ABNF illustrates their
expected wire representations, and the algorithms define the expected wire representations, and the algorithms define the
recommended way to produce them. Implementations <bcp14>MAY</bcp14> vary from the recommended way to produce them. Implementations <bcp14>MAY</bcp14> vary from the
specified behavior so long as the output is still correctly handled by specified behavior so long as the output is still correctly handled by
the parsing algorithm.</t> the parsing algorithm.</t>
</section> </section>
</section> </section>
<section anchor="specify" numbered="true" toc="default"> <section anchor="specify">
<name>Defining New Structured Fields</name> <name>Defining New Structured Fields</name>
<t>To specify a HTTP field as a Structured Field, its authors needs to:</t <t>To specify an HTTP field as a Structured Field, its authors need to:</t
> >
<ul spacing="normal"> <ul>
<li>Normatively reference this specification. Recipients and <li>Normatively reference this specification. Recipients and
generators of the field need to know that the requirements of this generators of the field need to know that the requirements of this
document are in effect.</li> document are in effect.</li>
<li>Identify whether the field is a Structured Header (i.e., it can <li>Identify whether the field is a Structured Header (i.e., it can
only be used in the header section - the common case), a Structured only be used in the header section -- the common case), a Structured
Trailer (only in the trailer section), or a Structured Field Trailer (only in the trailer section), or a Structured Field
(both).</li> (both).</li>
<li>Specify the type of the field value; either List (<xref <li>Specify the type of the field value; either List (<xref target="list
target="list" format="default"/>), Dictionary (<xref "/>), Dictionary (<xref target="dictionary"/>), or Item (<xref target="item"/>).
target="dictionary" format="default"/>), or Item (<xref target="item" </li>
format="default"/>).</li>
<li>Define the semantics of the field value.</li> <li>Define the semantics of the field value.</li>
<li>Specify any additional constraints upon the field value, as well <li>Specify any additional constraints upon the field value, as well
as the consequences when those constraints are violated.</li> as the consequences when those constraints are violated.</li>
</ul> </ul>
<t>Typically, this means that a field definition will specify the <t>Typically, this means that a field definition will specify the
top-level type - List, Dictionary or Item - and then define its top-level type -- List, Dictionary, or Item -- and then define its
allowable types, and constraints upon them. For example, a header allowable types and constraints upon them. For example, a header
defined as a List might have all Integer members, or a mix of types; a defined as a List might have all Integer members, or a mix of types; a
header defined as an Item might allow only Strings, and additionally header defined as an Item might allow only Strings, and additionally
only strings beginning with the letter "Q", or strings in only strings beginning with the letter "Q", or strings in
lowercase. Likewise, Inner Lists (<xref target="inner-list" lowercase. Likewise, Inner Lists (<xref target="inner-list"/>) are only va
format="default"/>) are only valid when a field definition explicitly lid when a field definition explicitly
allows them.</t> allows them.</t>
<t>When parsing fails, the entire field is ignored (see <xref <t>When parsing fails, the entire field is ignored (see <xref target="text
target="text-parse" format="default"/>); in most situations, violating -parse"/>); in most situations, violating
field-specific constraints should have the same effect. Thus, if a field-specific constraints should have the same effect. Thus, if a
header is defined as an Item and required to be an Integer, but a String header is defined as an Item and required to be an Integer, but a String
is received, the field will by default be ignored. If the field requires is received, the field will by default be ignored. If the field requires
different error handling, this should be explicitly specified.</t> different error handling, this should be explicitly specified.</t>
<t>Both Items and Inner Lists allow parameters as an extensibility <t>Both Items and Inner Lists allow parameters as an extensibility
mechanism; this means that values can later be extended to accommodate mechanism; this means that values can later be extended to accommodate
more information, if need be. To preserve forward compatibility, field more information, if need be. To preserve forward compatibility, field
specifications are discouraged from defining the presence of an specifications are discouraged from defining the presence of an
unrecognized Parameter as an error condition.</t> unrecognized parameter as an error condition.</t>
<t>To further assure that this extensibility is available in the future, <t>To further assure that this extensibility is available in the future,
and to encourage consumers to use a complete parser implementation, a and to encourage consumers to use a complete parser implementation, a
field definition can specify that "grease" Parameters be added by field definition can specify that "grease" parameters be added by
senders. A specification could stipulate that all Parameters that fit a senders. A specification could stipulate that all parameters that fit a
defined pattern are reserved for this use and then encourage them to be defined pattern are reserved for this use and then encourage them to be
sent on some portion of requests. This helps to discourage recipients sent on some portion of requests. This helps to discourage recipients
from writing a parser that does not account for Parameters.</t> from writing a parser that does not account for Parameters.</t>
<t>Specifications that use Dictionaries can also allow for forward <t>Specifications that use Dictionaries can also allow for forward
compatibility by requiring that the presence of - as well as value and compatibility by requiring that the presence of -- as well as value and
type associated with - unknown members be ignored. Later specifications type associated with -- unknown members be ignored. Later, specifications
can then add additional members, specifying constraints on them as can then add additional members, specifying constraints on them as
appropriate.</t> appropriate.</t>
<t>An extension to a structured field can then require that an entire <t>An extension to a Structured Field can then require that an entire
field value be ignored by a recipient that understands the extension if field value be ignored by a recipient that understands the extension if
constraints on the value it defines are not met.</t> constraints on the value it defines are not met.</t>
<t>A field definition cannot relax the requirements of this <t>A field definition cannot relax the requirements of this
specification because doing so would preclude handling by generic specification because doing so would preclude handling by generic
software; they can only add additional constraints (for example, on the software; they can only add additional constraints (for example, on the
numeric range of Integers and Decimals, the format of Strings and numeric range of Integers and Decimals, the format of Strings and
Tokens, the types allowed in a Dictionary's values, or the number of Tokens, the types allowed in a Dictionary's values, or the number of
Items in a List). Likewise, field definitions can only use this Items in a List). Likewise, field definitions can only use this
specification for the entire field value, not a portion thereof.</t> specification for the entire field value, not a portion thereof.</t>
<t>This specification defines minimums for the length or number of <t>This specification defines minimums for the length or number of
various structures supported by implementations. It does not specify various structures supported by implementations. It does not specify
maximum sizes in most cases, but authors should be aware that HTTP maximum sizes in most cases, but authors should be aware that HTTP
implementations do impose various limits on the size of individual implementations do impose various limits on the size of individual
fields, the total number of fields, and/or the size of the entire header fields, the total number of fields, and/or the size of the entire header
or trailer section.</t> or trailer section.</t>
<t>Specifications can refer to a field name as a "structured header <t>Specifications can refer to a field name as a "structured header
name", "structured trailer name" or "structured field name" as name", "structured trailer name", or "structured field name" as
appropriate. Likewise, they can refer its field value as a "structured appropriate. Likewise, they can refer its field value as a "structured
header value", "structured trailer value" or "structured field value" as header value", "structured trailer value", or "structured field value" as
necessary. Field definitions are encouraged to use the ABNF rules necessary.
Field definitions are encouraged to use the ABNF rules
beginning with "sf-" defined in this specification; other rules in this beginning with "sf-" defined in this specification; other rules in this
specification are not intended for their use.</t> specification are not intended to be used in field definitions.</t>
<t>For example, a fictitious Foo-Example header field might be specified <t>For example, a fictitious Foo-Example header field might be specified
as:</t> as:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
--8&lt;--
42. Foo-Example Header 42. Foo-Example Header
]]></artwork> </sourcecode>
<t>The Foo-Example HTTP header field conveys information about how <t>The Foo-Example HTTP header field conveys information about how
much Foo the message has.</t> much Foo the message has.</t>
<t>Foo-Example is an Item Structured Header [RFCxxxx]. Its value <bcp14>MU
<t>Foo-Example is a Item Structured Header [RFCxxxx]. Its value <bcp14>MUST</bcp ST</bcp14> be
14> be
an Integer (Section Y.Y of [RFCxxxx]). Its ABNF is:</t> an Integer (Section Y.Y of [RFCxxxx]). Its ABNF is:</t>
<sourcecode type="abnf">
<sourcecode type="abnf"><![CDATA[
Foo-Example = sf-integer Foo-Example = sf-integer
]]></sourcecode> </sourcecode>
<t>Its value indicates the amount of Foo in the message, and it <bcp14>MUS
<t>Its value indicates the amount of Foo in the message, and <bcp14>MUST</bcp14> T</bcp14>
be between 0 and 10, inclusive; other values <bcp14>MUST</bcp14> cause be between 0 and 10, inclusive; other values <bcp14>MUST</bcp14> cause
the entire header field to be ignored.</t> the entire header field to be ignored.</t>
<t>The following parameter is defined:</t>
<t>The following parameters are defined: <ul>
* A Parameter whose name is "foourl", and whose value is a String <li>A parameter whose name is "foourl", and whose value is a String
(Section Y.Y of [RFCxxxx]), conveying the Foo URL (Section Y.Y of [RFCxxxx]), conveying the Foo URL
for the message. See below for processing requirements.</t> for the message. See below for processing requirements.</li>
</ul>
<t>"foourl" contains a URI-reference (<xref target="RFC3986" <t>"foourl" contains a URI-reference (Section 4.1 of [RFC3986]). If
sectionFormat="of" section="4.1"/>). If
its value is not a valid URI-reference, the entire header field its value is not a valid URI-reference, the entire header field
<bcp14>MUST</bcp14> be ignored. If its value is a relative reference (<xref <bcp14>MUST</bcp14> be ignored. If its value is a relative reference (Section 4.
target="RFC3986" sectionFormat="of" section="4.2"/>), it <bcp14>MUST</bcp14> 2 of [RFC3986]), it <bcp14>MUST</bcp14>
be resolved (<xref target="RFC3986" sectionFormat="of" section="5"/>) before be resolved (Section 5 of [RFC3986]) before
being used.</t> being used.</t>
<t>For example:</t>
<t>For example:</t> <sourcecode type="http-structured-fields">
<artwork type="" name="" align="left" alt=""><![CDATA[
Foo-Example: 2; foourl="https://foo.example.com/" Foo-Example: 2; foourl="https://foo.example.com/"
]]></artwork> --&gt;8--
</sourcecode>
</section> </section>
<section anchor="types" numbered="true" toc="default"> <section anchor="types">
<name>Structured Data Types</name> <name>Structured Data Types</name>
<t>This section defines the abstract types for Structured Fields. The <t>This section defines the abstract types for Structured Fields. The
ABNF provided represents the on-wire format in HTTP field values.</t> ABNF provided represents the on-wire format in HTTP field values.</t>
<t>In summary:</t> <t>In summary:</t>
<ul spacing="normal"> <ul>
<li>There are three top-level types that a HTTP field can be defined <li>There are three top-level types that an HTTP field can be defined
as: Lists, Dictionaries, and Items.</li> as: Lists, Dictionaries, and Items.</li>
<li>Lists and Dictionaries are containers; their members can be Items <li>Lists and Dictionaries are containers; their members can be Items
or Inner Lists (which are themselves arrays of Items).</li> or Inner Lists (which are themselves arrays of Items).</li>
<li>Both Items and Inner Lists can be parameterized with key/value pairs .</li> <li>Both Items and Inner Lists can be Parameterized with key/value pairs .</li>
</ul> </ul>
<section anchor="list" numbered="true" toc="default"> <section anchor="list">
<name>Lists</name> <name>Lists</name>
<t>Lists are arrays of zero or more members, each of which can be an <t>Lists are arrays of zero or more members, each of which can be an
Item (<xref target="item" format="default"/>) or an Inner List (<xref Item (<xref target="item"/>) or an Inner List (<xref target="inner-list"/
target="inner-list" format="default"/>), both of which can be >), both of which can be
Parameterized (<xref target="param" format="default"/>).</t> Parameterized (<xref target="param"/>).</t>
<t>The ABNF for Lists in HTTP fields is:</t> <t>The ABNF for Lists in HTTP fields is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-list = list-member *( OWS "," OWS list-member ) sf-list = list-member *( OWS "," OWS list-member )
list-member = sf-item / inner-list list-member = sf-item / inner-list
]]></sourcecode> </sourcecode>
<t>Each member is separated by a comma and optional whitespace. For <t>Each member is separated by a comma and optional whitespace. For
example, a field whose value is defined as a List of Strings could example, a field whose value is defined as a List of Strings could
look like:</t> look like:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-StrList: "foo", "bar", "It was the best of times." Example-StrList: "foo", "bar", "It was the best of times."
]]></artwork> </sourcecode>
<t>An empty List is denoted by not serializing the field at all. This <t>An empty List is denoted by not serializing the field at all. This
implies that fields defined as Lists have a default empty value.</t> implies that fields defined as Lists have a default empty value.</t>
<t>Note that Lists can have their members split across multiple lines <t>Note that Lists can have their members split across multiple lines
inside a header or trailer section, as per <xref target="RFC7230" inside a header or trailer section, as per <xref target="RFC7230" section
sectionFormat="of" section="3.2.2"/>; for example, the following are ="3.2.2"/>; for example, the following are
equivalent:</t> equivalent:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Hdr: foo, bar Example-Hdr: foo, bar
]]></artwork> </sourcecode>
<t>and</t> <t>and</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Hdr: foo Example-Hdr: foo
Example-Hdr: bar Example-Hdr: bar
]]></artwork> </sourcecode>
<t>However, individual members of a List cannot be safely split <t>However, individual members of a List cannot be safely split
between across lines; see <xref target="text-parse" format="default"/> between lines; see <xref target="text-parse"/>
for details.</t> for details.</t>
<t>Parsers <bcp14>MUST</bcp14> support Lists containing at least 1024 me mbers. Field <t>Parsers <bcp14>MUST</bcp14> support Lists containing at least 1024 me mbers. Field
specifications can constrain the types and cardinality of individual specifications can constrain the types and cardinality of individual
List values as they require.</t> List values as they require.</t>
<section anchor="inner-list" numbered="true" toc="default"> <section anchor="inner-list">
<name>Inner Lists</name> <name>Inner Lists</name>
<t>An Inner List is an array of zero or more Items (<xref <t>An Inner List is an array of zero or more Items (<xref target="item
target="item" format="default"/>). Both the individual Items and the "/>). Both the individual Items and the
Inner List itself can be Parameterized (<xref target="param" Inner List itself can be Parameterized (<xref target="param"/>).</t>
format="default"/>).</t>
<t>The ABNF for Inner Lists is:</t> <t>The ABNF for Inner Lists is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
inner-list = "(" *SP [ sf-item *( 1*SP sf-item ) *SP ] ")" inner-list = "(" *SP [ sf-item *( 1*SP sf-item ) *SP ] ")"
parameters parameters
]]></sourcecode> </sourcecode>
<t>Inner Lists are denoted by surrounding parenthesis, and have <t>Inner Lists are denoted by surrounding parenthesis, and
their values delimited by one or more spaces. A field whose value is their values are delimited by one or more spaces. A field whose value i
s
defined as a List of Inner Lists of Strings could look like:</t> defined as a List of Inner Lists of Strings could look like:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-StrListList: ("foo" "bar"), ("baz"), ("bat" "one"), () Example-StrListList: ("foo" "bar"), ("baz"), ("bat" "one"), ()
]]></artwork> </sourcecode>
<t>Note that the last member in this example is an empty Inner List.</ t> <t>Note that the last member in this example is an empty Inner List.</ t>
<t>A header field whose value is defined as a List of Inner Lists <t>A header field whose value is defined as a List of Inner Lists
with Parameters at both levels could look like:</t> with Parameters at both levels could look like:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-ListListParam: ("foo"; a=1;b=2);lvl=5, ("bar" "baz");lvl=1 Example-ListListParam: ("foo"; a=1;b=2);lvl=5, ("bar" "baz");lvl=1
]]></artwork> </sourcecode>
<t>Parsers <bcp14>MUST</bcp14> support Inner Lists containing at least 256 <t>Parsers <bcp14>MUST</bcp14> support Inner Lists containing at least 256
members. Field specifications can constrain the types and members. Field specifications can constrain the types and
cardinality of individual Inner List members as they require.</t> cardinality of individual Inner List members as they require.</t>
</section> </section>
<section anchor="param" numbered="true" toc="default"> <section anchor="param">
<name>Parameters</name> <name>Parameters</name>
<t>Parameters are an ordered map of key-value pairs that are <t>Parameters are an ordered map of key-value pairs that are
associated with an Item (<xref target="item" format="default"/>) or associated with an Item (<xref target="item"/>) or
Inner List (<xref target="inner-list" format="default"/>). The keys Inner List (<xref target="inner-list"/>).
are unique within the scope the Parameters they occur within, and The keys
are unique within the scope of the Parameters they occur within, and
the values are bare items (i.e., they themselves cannot be the values are bare items (i.e., they themselves cannot be
parameterized; see <xref target="item" format="default"/>).</t> parameterized; see <xref target="item"/>).</t>
<t>The ABNF for Parameters is:</t> <t>The ABNF for Parameters is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
parameters = *( ";" *SP parameter ) parameters = *( ";" *SP parameter )
parameter = param-name [ "=" param-value ] parameter = param-name [ "=" param-value ]
param-name = key param-name = key
key = ( lcalpha / "*" ) key = ( lcalpha / "*" )
*( lcalpha / DIGIT / "_" / "-" / "." / "*" ) *( lcalpha / DIGIT / "_" / "-" / "." / "*" )
lcalpha = %x61-7A ; a-z lcalpha = %x61-7A ; a-z
param-value = bare-item param-value = bare-item
]]></sourcecode> </sourcecode>
<t>Note that Parameters are ordered as serialized, and Parameter <t>Note that parameters are ordered as serialized, and parameter
keys cannot contain uppercase letters. A parameter is separated from keys cannot contain uppercase letters. A parameter is separated from
its Item or Inner List and other parameters by a semicolon. For its Item or Inner List and other parameters by a semicolon. For
example:</t> example:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-ParamList: abc;a=1;b=2; cde_456, (ghi;jk=4 l);q="9";r=w Example-ParamList: abc;a=1;b=2; cde_456, (ghi;jk=4 l);q="9";r=w
]]></artwork> </sourcecode>
<t>Parameters whose value is Boolean (see <xref target="boolean" <t>Parameters whose value is Boolean (see <xref target="boolean"/>) tr
format="default"/>) true <bcp14>MUST</bcp14> omit that value when seria ue <bcp14>MUST</bcp14> omit that value when serialized. For
lized. For
example, the "a" parameter here is true, while the "b" parameter is example, the "a" parameter here is true, while the "b" parameter is
false:</t> false:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Int: 1; a; b=?0 Example-Int: 1; a; b=?0
]]></artwork> </sourcecode>
<t>Note that this requirement is only on serialization; parsers are <t>Note that this requirement is only on serialization; parsers are
still required to correctly handle the true value when it appears in still required to correctly handle the true value when it appears in
a parameter.</t> a parameter.</t>
<t>Parsers <bcp14>MUST</bcp14> support at least 256 parameters on an I tem or Inner <t>Parsers <bcp14>MUST</bcp14> support at least 256 parameters on an I tem or Inner
List, and support parameter keys with at least 64 characters. Field List, and support parameter keys with at least 64 characters. Field
specifications can constrain the order of individual Parameters, as specifications can constrain the order of individual parameters, as
well as their values' types as required.</t> well as their values' types as required.</t>
</section> </section>
</section> </section>
<section anchor="dictionary" numbered="true" toc="default"> <section anchor="dictionary">
<name>Dictionaries</name> <name>Dictionaries</name>
<t>Dictionaries are ordered maps of name-value pairs, where the names <t>Dictionaries are ordered maps of name-value pairs, where the names
are short textual strings and the values are Items (<xref are short textual strings and the values are Items (<xref target="item"/>
target="item" format="default"/>) or arrays of Items, both of which ) or arrays of Items, both of which
can be Parameterized (<xref target="param" format="default"/>). There can be Parameterized (<xref target="param"/>). There
can be zero or more members, and their names are unique in the scope can be zero or more members, and their names are unique in the scope
of the Dictionary they occur within.</t> of the Dictionary they occur within.</t>
<t>Implementations <bcp14>MUST</bcp14> provide access to Dictionaries bo th by index <t>Implementations <bcp14>MUST</bcp14> provide access to Dictionaries bo th by index
and by name. Specifications <bcp14>MAY</bcp14> use either means of access ing the and by name. Specifications <bcp14>MAY</bcp14> use either means of access ing the
members.</t> members.</t>
<t>The ABNF for Dictionaries is:</t> <t>The ABNF for Dictionaries is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-dictionary = dict-member *( OWS "," OWS dict-member ) sf-dictionary = dict-member *( OWS "," OWS dict-member )
dict-member = member-name [ "=" member-value ] dict-member = member-name ( parameters / ( "=" member-value ))
member-name = key member-name = key
member-value = sf-item / inner-list member-value = sf-item / inner-list
]]></sourcecode> </sourcecode>
<t>Members are ordered as serialized, and separated by a comma with <t>Members are ordered as serialized and separated by a comma with
optional whitespace. Member names cannot contain uppercase optional whitespace. Member names cannot contain uppercase
characters. Names and values are separated by "=" (without characters. Names and values are separated by "=" (without
whitespace). For example:</t> whitespace). For example:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Dict: en="Applepie", da=:w4ZibGV0w6ZydGU=: Example-Dict: en="Applepie", da=:w4ZibGV0w6ZydGU=:
]]></artwork> </sourcecode>
<t>Note that in this example, the final "=" is due to the inclusion of <t>Note that in this example, the final "=" is due to the inclusion of
a Byte Sequence; see <xref target="binary" format="default"/>.</t> a Byte Sequence; see <xref target="binary"/>.</t>
<t>Members whose value is Boolean (see <xref target="boolean" <t>Members whose value is Boolean (see <xref target="boolean"/>) true <b
format="default"/>) true <bcp14>MUST</bcp14> omit that value when seriali cp14>MUST</bcp14> omit that value when serialized. For
zed. For
example, here both "b" and "c" are true:</t> example, here both "b" and "c" are true:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Dict: a=?0, b, c; foo=bar Example-Dict: a=?0, b, c; foo=bar
]]></artwork> </sourcecode>
<t>Note that this requirement is only on serialization; parsers are <t>Note that this requirement is only on serialization; parsers are
still required to correctly handle the true Boolean value when it still required to correctly handle the true Boolean value when it
appears in Dictionary values.</t> appears in Dictionary values.</t>
<t>A Dictionary with a member whose value is an Inner List of Tokens:</t > <t>A Dictionary with a member whose value is an Inner List of Tokens:</t >
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-DictList: rating=1.5, feelings=(joy sadness) Example-DictList: rating=1.5, feelings=(joy sadness)
]]></artwork> </sourcecode>
<t>A Dictionary with a mix of Items and Inner Lists, some with Parameter <t>A Dictionary with a mix of Items and Inner Lists, some with parameter
s:</t> s:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-MixDict: a=(1 2), b=3, c=4;aa=bb, d=(5 6);valid Example-MixDict: a=(1 2), b=3, c=4;aa=bb, d=(5 6);valid
]]></artwork> </sourcecode>
<t>As with lists, an empty Dictionary is represented by omitting the <t>As with Lists, an empty Dictionary is represented by omitting the
entire field. This implies that fields defined as Dictionaries have a entire field. This implies that fields defined as Dictionaries have a
default empty value.</t> default empty value.</t>
<t>Typically, a field specification will define the semantics of <t>Typically, a field specification will define the semantics of
Dictionaries by specifying the allowed type(s) for individual members Dictionaries by specifying the allowed type(s) for individual members
by their names, as well as whether their presence is required or by their names, as well as whether their presence is required or
optional. Recipients <bcp14>MUST</bcp14> ignore names that are undefined or unknown, optional. Recipients <bcp14>MUST</bcp14> ignore names that are undefined or unknown,
unless the field's specification specifically disallows them.</t> unless the field's specification specifically disallows them.</t>
<t>Note that Dictionaries can have their members split across multiple <t>Note that Dictionaries can have their members split across multiple
lines inside a header or trailer section; for example, the following lines inside a header or trailer section; for example, the following
are equivalent:</t> are equivalent:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Hdr: foo=1, bar=2 Example-Hdr: foo=1, bar=2
]]></artwork> </sourcecode>
<t>and</t> <t>and</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Hdr: foo=1 Example-Hdr: foo=1
Example-Hdr: bar=2 Example-Hdr: bar=2
]]></artwork> </sourcecode>
<t>However, individual members of a Dictionary cannot be safely split <t>However, individual members of a Dictionary cannot be safely split
between lines; see <xref target="text-parse" format="default"/> for between lines; see <xref target="text-parse"/> for
details.</t> details.</t>
<t>Parsers <bcp14>MUST</bcp14> support Dictionaries containing at least 1024 <t>Parsers <bcp14>MUST</bcp14> support Dictionaries containing at least 1024
name/value pairs, and names with at least 64 characters. Field name/value pairs and names with at least 64 characters. Field
specifications can constrain the order of individual Dictionary specifications can constrain the order of individual Dictionary
members, as well as their values' types as required.</t> members, as well as their values' types as required.</t>
</section> </section>
<section anchor="item" numbered="true" toc="default"> <section anchor="item">
<name>Items</name> <name>Items</name>
<t>An Item can be a Integer (<xref target="integer" <t>An Item can be an Integer (<xref target="integer"/>), a Decimal (<xre
format="default"/>), Decimal (<xref target="decimal" f target="decimal"/>), a String (<xref target="string"/>), a Token (<xref target
format="default"/>), String (<xref target="string" ="token"/>),
format="default"/>), Token (<xref target="token" format="default"/>), a Byte Sequence (<xref target="binary"/>), or a Boolean
Byte Sequence (<xref target="binary" format="default"/>), or Boolean (<xref target="boolean"/>). It can have associated
(<xref target="boolean" format="default"/>). It can have associated parameters (<xref target="param"/>).</t>
Parameters (<xref target="param" format="default"/>).</t>
<t>The ABNF for Items is:</t> <t>The ABNF for Items is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-item = bare-item parameters sf-item = bare-item parameters
bare-item = sf-integer / sf-decimal / sf-string / sf-token bare-item = sf-integer / sf-decimal / sf-string / sf-token
/ sf-binary / sf-boolean / sf-binary / sf-boolean
]]></sourcecode> </sourcecode>
<t>For example, a header field that is defined to be an Item that is <t>For example, a header field that is defined to be an Item that is
an Integer might look like:</t> an Integer might look like:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-IntItemHeader: 5 Example-IntItemHeader: 5
]]></artwork> </sourcecode>
<t>or with Parameters:</t> <t>or with parameters:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-IntItem: 5; foo=bar Example-IntItem: 5; foo=bar
]]></artwork> </sourcecode>
<section anchor="integer" numbered="true" toc="default"> <section anchor="integer">
<name>Integers</name> <name>Integers</name>
<t>Integers have a range of -999,999,999,999,999 to <t>Integers have a range of -999,999,999,999,999 to
999,999,999,999,999 inclusive (i.e., up to fifteen digits, signed), 999,999,999,999,999 inclusive (i.e., up to fifteen digits, signed),
for IEEE 754 compatibility (<xref target="IEEE754" for IEEE 754 compatibility <xref target="IEEE754"/>.</t>
format="default"/>).</t>
<t>The ABNF for Integers is:</t> <t>The ABNF for Integers is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-integer = ["-"] 1*15DIGIT sf-integer = ["-"] 1*15DIGIT
]]></sourcecode> </sourcecode>
<t>For example:</t> <t>For example:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Integer: 42 Example-Integer: 42
]]></artwork> </sourcecode>
<t>Integers larger than 15 digits can be supported in a variety of <t>Integers larger than 15 digits can be supported in a variety of
ways; for example, by using a String (<xref target="string" ways; for example, by using a String (<xref target="string"/>), a Byte
format="default"/>), Byte Sequence (<xref target="binary" Sequence (<xref target="binary"/>), or a parameter on an Integer that acts as a
format="default"/>), or a parameter on an Integer that acts as a
scaling factor.</t> scaling factor.</t>
<t>While it is possible to serialise Integers with leading zeros <t>While it is possible to serialize Integers with leading zeros
(e.g., "0002", "-01") and signed zero ("-0"), these distinctions may (e.g., "0002", "-01") and signed zero ("-0"), these distinctions may
not be preserved by implementations.</t> not be preserved by implementations.</t>
<t>Note that commas in Integers are used in this section's prose <t>Note that commas in Integers are used in this section's prose
only for readability; they are not valid in the wire format.</t> only for readability; they are not valid in the wire format.</t>
</section> </section>
<section anchor="decimal" numbered="true" toc="default"> <section anchor="decimal">
<name>Decimals</name> <name>Decimals</name>
<t>Decimals are numbers with an integer and a fractional <t>Decimals are numbers with an integer and a fractional
component. The integer component has at most 12 digits; the component. The integer component has at most 12 digits; the
fractional component has at most three digits.</t> fractional component has at most three digits.</t>
<t>The ABNF for decimals is:</t> <t>The ABNF for decimals is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-decimal = ["-"] 1*12DIGIT "." 1*3DIGIT sf-decimal = ["-"] 1*12DIGIT "." 1*3DIGIT
]]></sourcecode> </sourcecode>
<t>For example, a header whose value is defined as a Decimal could <t>For example, a header whose value is defined as a Decimal could
look like:</t> look like:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Decimal: 4.5 Example-Decimal: 4.5
]]></artwork> </sourcecode>
<t>While it is possible to serialise Decimals with leading zeros <t>While it is possible to serialize Decimals with leading zeros
(e.g., "0002.5", "-01.334"), trailing zeros (e.g., "5.230", (e.g., "0002.5", "-01.334"), trailing zeros (e.g., "5.230",
"-0.40"), and signed zero (e.g., "-0.0"), these distinctions may not "-0.40"), and signed zero (e.g., "-0.0"), these distinctions may not
be preserved by implementations.</t> be preserved by implementations.</t>
<t>Note that the serialisation algorithm (<xref target="ser-decimal" <t>Note that the serialization algorithm (<xref target="ser-decimal"/>
format="default"/>) rounds input with more than three digits of ) rounds input with more than three digits of
precision in the fractional component. If an alternative rounding precision in the fractional component. If an alternative rounding
strategy is desired, this should be specified by the header strategy is desired, this should be specified by the header
definition to occur before serialisation.</t> definition to occur before serialization.</t>
</section> </section>
<section anchor="string" numbered="true" toc="default"> <section anchor="string">
<name>Strings</name> <name>Strings</name>
<t>Strings are zero or more printable ASCII <xref target="RFC0020" <t>Strings are zero or more printable ASCII <xref target="RFC0020"/> c
format="default"/> characters (i.e., the range %x20 to %x7E). Note haracters (i.e., the range %x20 to %x7E). Note
that this excludes tabs, newlines, carriage returns, etc.</t> that this excludes tabs, newlines, carriage returns, etc.</t>
<t>The ABNF for Strings is:</t> <t>The ABNF for Strings is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-string = DQUOTE *chr DQUOTE sf-string = DQUOTE *chr DQUOTE
chr = unescaped / escaped chr = unescaped / escaped
unescaped = %x20-21 / %x23-5B / %x5D-7E unescaped = %x20-21 / %x23-5B / %x5D-7E
escaped = "\" ( DQUOTE / "\" ) escaped = "\" ( DQUOTE / "\" )
]]></sourcecode> </sourcecode>
<t>Strings are delimited with double quotes, using a backslash ("\") <t>Strings are delimited with double quotes, using a backslash ("\")
to escape double quotes and backslashes. For example:</t> to escape double quotes and backslashes. For example:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-String: "hello world" Example-String: "hello world"
]]></artwork> </sourcecode>
<t>Note that Strings only use DQUOTE as a delimiter; single quotes <t>Note that Strings only use DQUOTE as a delimiter; single quotes
do not delimit Strings. Furthermore, only DQUOTE and "\" can be do not delimit Strings. Furthermore, only DQUOTE and "\" can be
escaped; other characters after "\" <bcp14>MUST</bcp14> cause parsing t o fail.</t> escaped; other characters after "\" <bcp14>MUST</bcp14> cause parsing t o fail.</t>
<t>Unicode is not directly supported in Strings, because it causes a <t>Unicode is not directly supported in Strings, because it causes a
number of interoperability issues, and - with few exceptions - field number of interoperability issues, and -- with few exceptions -- field
values do not require it.</t> values do not require it.</t>
<t>When it is necessary for a field value to convey non-ASCII <t>When it is necessary for a field value to convey non-ASCII
content, a Byte Sequence (<xref target="binary" format="default"/>) content, a Byte Sequence (<xref target="binary"/>)
can be specified, along with a character encoding (preferably <xref can be specified, along with a character encoding (preferably <xref tar
target="RFC3629" format="default"/>).</t> get="RFC3629"/>).</t>
<t>Parsers <bcp14>MUST</bcp14> support Strings (after any decoding) wi th at least <t>Parsers <bcp14>MUST</bcp14> support Strings (after any decoding) wi th at least
1024 characters.</t> 1024 characters.</t>
</section> </section>
<section anchor="token" numbered="true" toc="default"> <section anchor="token">
<name>Tokens</name> <name>Tokens</name>
<t>Tokens are short textual words; their abstract model is identical <t>Tokens are short textual words; their abstract model is identical
to their expression in the HTTP field value serialization.</t> to their expression in the HTTP field value serialization.</t>
<t>The ABNF for Tokens is:</t> <t>The ABNF for Tokens is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-token = ( ALPHA / "*" ) *( tchar / ":" / "/" ) sf-token = ( ALPHA / "*" ) *( tchar / ":" / "/" )
]]></sourcecode> </sourcecode>
<t>For example:</t> <t>For example:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Token: foo123/456 Example-Token: foo123/456
]]></artwork> </sourcecode>
<t>Parsers <bcp14>MUST</bcp14> support Tokens with at least 512 charac ters.</t> <t>Parsers <bcp14>MUST</bcp14> support Tokens with at least 512 charac ters.</t>
<t>Note that Token allows the same characters as the "token" ABNF <t>Note that Token allows the same characters as the "token" ABNF
rule defined in <xref target="RFC7230" format="default"/>, with the rule defined in <xref target="RFC7230"/>, with the
exceptions that the first character is required to be either ALPHA exceptions that the first character is required to be either ALPHA
or "*", and ":" and "/" are also allowed in subsequent or "*", and ":" and "/" are also allowed in subsequent
characters.</t> characters.</t>
</section> </section>
<section anchor="binary" numbered="true" toc="default"> <section anchor="binary">
<name>Byte Sequences</name> <name>Byte Sequences</name>
<t>Byte Sequences can be conveyed in Structured Fields.</t> <t>Byte Sequences can be conveyed in Structured Fields.</t>
<t>The ABNF for a Byte Sequence is:</t> <t>The ABNF for a Byte Sequence is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-binary = ":" *(base64) ":" sf-binary = ":" *(base64) ":"
base64 = ALPHA / DIGIT / "+" / "/" / "=" base64 = ALPHA / DIGIT / "+" / "/" / "="
]]></sourcecode> </sourcecode>
<t>A Byte Sequence is delimited with colons and encoded using base64 <t>A Byte Sequence is delimited with colons and encoded using base64
(<xref target="RFC4648" sectionFormat="comma" section="4"/>). For (<xref target="RFC4648" sectionFormat="comma" section="4"/>). For
example:</t> example:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Binary: :cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==: Example-Binary: :cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==:
]]></artwork> </sourcecode>
<t>Parsers <bcp14>MUST</bcp14> support Byte Sequences with at least 16 384 octets <t>Parsers <bcp14>MUST</bcp14> support Byte Sequences with at least 16 384 octets
after decoding.</t> after decoding.</t>
</section> </section>
<section anchor="boolean" numbered="true" toc="default"> <section anchor="boolean">
<name>Booleans</name> <name>Booleans</name>
<t>Boolean values can be conveyed in Structured Fields.</t> <t>Boolean values can be conveyed in Structured Fields.</t>
<t>The ABNF for a Boolean is:</t> <t>The ABNF for a Boolean is:</t>
<sourcecode type="abnf"><![CDATA[ <sourcecode type="abnf">
sf-boolean = "?" boolean sf-boolean = "?" boolean
boolean = "0" / "1" boolean = "0" / "1"
]]></sourcecode> </sourcecode>
<t>A Boolean is indicated with a leading "?" character followed by a <t>A Boolean is indicated with a leading "?" character followed by a
"1" for a true value or "0" for false. For example:</t> "1" for a true value or "0" for false. For example:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-Bool: ?1 Example-Bool: ?1
]]></artwork> </sourcecode>
<t>Note that in Dictionary (<xref target="dictionary" <t>Note that in Dictionary (<xref target="dictionary"/>) and Parameter
format="default"/>) and Parameter (<xref target="param" (<xref target="param"/>) values, Boolean true is indicated by omitting
format="default"/>) values, Boolean true is indicated by omitting
the value.</t> the value.</t>
</section> </section>
</section> </section>
</section> </section>
<section anchor="text" numbered="true" toc="default"> <section anchor="text">
<name>Working With Structured Fields in HTTP</name> <name>Working with Structured Fields in HTTP</name>
<t>This section defines how to serialize and parse Structured Fields in <t>This section defines how to serialize and parse Structured Fields in
textual HTTP field values and other encodings compatible with them textual HTTP field values and other encodings compatible with them
(e.g., in HTTP/2 <xref target="RFC7540" format="default"/> before (e.g., in HTTP/2 <xref target="RFC7540"/> before
compression with HPACK <xref target="RFC7541" format="default"/>).</t> compression with HPACK <xref target="RFC7541"/>).</t>
<section anchor="text-serialize" numbered="true" toc="default"> <section anchor="text-serialize">
<name>Serializing Structured Fields</name> <name>Serializing Structured Fields</name>
<t>Given a structure defined in this specification, return an ASCII <t>Given a structure defined in this specification, return an ASCII
string suitable for use in a HTTP field value.</t> string suitable for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If the structure is a Dictionary or List and its value is empty <li>If the structure is a Dictionary or List and its value is empty
(i.e., it has no members), do not serialize the field at all (i.e., (i.e., it has no members), do not serialize the field at all (i.e.,
omit both the field-name and field-value).</li> omit both the field-name and field-value).</li>
<li>If the structure is a List, let output_string be the result of <li>If the structure is a List, let output_string be the result of
running Serializing a List (<xref target="ser-list" running Serializing a List (<xref target="ser-list"/>) with the structu
format="default"/>) with the structure.</li> re.</li>
<li>Else if the structure is a Dictionary, let output_string be the <li>Else, if the structure is a Dictionary, let output_string be the
result of running Serializing a Dictionary (<xref result of running Serializing a Dictionary (<xref target="ser-dictionar
target="ser-dictionary" format="default"/>) with the structure.</li> y"/>) with the structure.</li>
<li>Else if the structure is an Item, let output_string be the <li>Else, if the structure is an Item, let output_string be the
result of running Serializing an Item (<xref target="ser-item" result of running Serializing an Item (<xref target="ser-item"/>) with
format="default"/>) with the structure.</li> the structure.</li>
<li>Else, fail serialization.</li> <li>Else, fail serialization.</li>
<li>Return output_string converted into an array of bytes, using <li>Return output_string converted into an array of bytes, using
ASCII encoding <xref target="RFC0020" format="default"/>.</li> ASCII encoding <xref target="RFC0020"/>.</li>
</ol> </ol>
<section anchor="ser-list" numbered="true" toc="default"> <section anchor="ser-list">
<name>Serializing a List</name> <name>Serializing a List</name>
<t>Given an array of (member_value, parameters) tuples as <t>Given an array of (member_value, parameters) tuples as
input_list, return an ASCII string suitable for use in a HTTP field input_list, return an ASCII string suitable for use in an HTTP field
value.</t> value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li> <li>
<t>For each (member_value, parameters) of input_list: <t>For each (member_value, parameters) of input_list:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>If member_value is an array, append the result of running <li>If member_value is an array, append the result of running
Serializing an Inner List (<xref target="ser-innerlist" Serializing an Inner List (<xref target="ser-innerlist"/>) with (
format="default"/>) with (member_value, parameters) to member_value, parameters) to
output.</li> output.</li>
<li>Otherwise, append the result of running Serializing an <li>Otherwise, append the result of running Serializing an
Item (<xref target="ser-item" format="default"/>) with Item (<xref target="ser-item"/>) with
(member_value, parameters) to output.</li> (member_value, parameters) to output.</li>
<li> <li>
<t>If more member_values remain in input_list: <t>If more member_values remain in input_list:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append "," to output.</li> <li>Append "," to output.</li>
<li>Append a single SP to output.</li> <li>Append a single SP to output.</li>
</ol> </ol>
</li> </li>
</ol> </ol>
</li> </li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
<section anchor="ser-innerlist" numbered="true" toc="default"> <section anchor="ser-innerlist">
<name>Serializing an Inner List</name> <name>Serializing an Inner List</name>
<t>Given an array of (member_value, parameters) tuples as <t>Given an array of (member_value, parameters) tuples as
inner_list, and parameters as list_parameters, return an ASCII inner_list, and parameters as list_parameters, return an ASCII
string suitable for use in a HTTP field value.</t> string suitable for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let output be the string "(".</li> <li>Let output be the string "(".</li>
<li> <li>
<t>For each (member_value, parameters) of inner_list: <t>For each (member_value, parameters) of inner_list:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append the result of running Serializing an Item (<xref <li>Append the result of running Serializing an Item (<xref ta
target="ser-item" format="default"/>) with (member_value, rget="ser-item"/>) with (member_value,
parameters) to output.</li> parameters) to output.</li>
<li>If more values remain in inner_list, append a single SP to output.</li> <li>If more values remain in inner_list, append a single SP to output.</li>
</ol> </ol>
</li> </li>
<li>Append ")" to output.</li> <li>Append ")" to output.</li>
<li>Append the result of running Serializing Parameters (<xref <li>Append the result of running Serializing Parameters (<xref tar
target="ser-params" format="default"/>) with list_parameters to get="ser-params"/>) with list_parameters to
output.</li> output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
<section anchor="ser-params" numbered="true" toc="default"> <section anchor="ser-params">
<name>Serializing Parameters</name> <name>Serializing Parameters</name>
<t>Given an ordered Dictionary as input_parameters (each member <t>Given an ordered Dictionary as input_parameters (each member
having a param_name and a param_value), return an ASCII string having a param_name and a param_value), return an ASCII string
suitable for use in a HTTP field value.</t> suitable for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li> <li>
<t>For each param_name with a value of param_value in input_para meters: <t>For each param_name with a value of param_value in input_para meters:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append ";" to output.</li> <li>Append ";" to output.</li>
<li>Append the result of running Serializing a Key (<xref <li>Append the result of running Serializing a Key (<xref targ
target="ser-key" format="default"/>) with param_name to et="ser-key"/>) with param_name to
output.</li> output.</li>
<li> <li>
<t>If param_value is not Boolean true: <t>If param_value is not Boolean true:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append "=" to output.</li> <li>Append "=" to output.</li>
<li>Append the result of running Serializing a bare Item <li>Append the result of running Serializing a bare Item
(<xref target="ser-bare-item" format="default"/>) with (<xref target="ser-bare-item"/>) with
param_value to output.</li> param_value to output.</li>
</ol> </ol>
</li> </li>
</ol> </ol>
</li> </li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
<section anchor="ser-key" numbered="true" toc="default"> <section anchor="ser-key">
<name>Serializing a Key</name> <name>Serializing a Key</name>
<t>Given a key as input_key, return an ASCII string suitable for <t>Given a key as input_key, return an ASCII string suitable for
use in a HTTP field value.</t> use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Convert input_key into a sequence of ASCII characters; if <li>Convert input_key into a sequence of ASCII characters; if
conversion fails, fail serialization.</li> conversion fails, fail serialization.</li>
<li>If input_key contains characters not in lcalpha, DIGIT, "_", <li>If input_key contains characters not in lcalpha, DIGIT, "_",
"-", ".", or "*" fail serialization.</li> "-", ".", or "*", fail serialization.</li>
<li>If the first character of input_key is not lcalpha or "*", <li>If the first character of input_key is not lcalpha or "*",
fail serialization.</li> fail serialization.</li>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li>Append input_key to output.</li> <li>Append input_key to output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
</section> </section>
<section anchor="ser-dictionary" numbered="true" toc="default"> <section anchor="ser-dictionary">
<name>Serializing a Dictionary</name> <name>Serializing a Dictionary</name>
<t>Given an ordered Dictionary as input_dictionary (each member <t>Given an ordered Dictionary as input_dictionary (each member
having a member_name and a tuple value of (member_value, having a member_name and a tuple value of (member_value,
parameters)), return an ASCII string suitable for use in a HTTP parameters)), return an ASCII string suitable for use in an HTTP
field value.</t> field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li> <li>
<t>For each member_name with a value of (member_value, parameters) in input_dictionary: <t>For each member_name with a value of (member_value, parameters) in input_dictionary:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append the result of running Serializing a Key (<xref <li>Append the result of running Serializing a Key (<xref target
target="ser-key" format="default"/>) with member's member_name ="ser-key"/>) with member's member_name
to output.</li> to output.</li>
<li> <li>
<t>If member_value is Boolean true: <t>If member_value is Boolean true:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append the result of running Serializing Parameters <li>Append the result of running Serializing Parameters
(<xref target="ser-params" format="default"/>) with (<xref target="ser-params"/>) with
parameters to output.</li> parameters to output.</li>
</ol> </ol>
</li> </li>
<li> <li>
<t>Otherwise: <t>Otherwise:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append "=" to output.</li> <li>Append "=" to output.</li>
<li>If member_value is an array, append the result of <li>If member_value is an array, append the result of
running Serializing an Inner List (<xref running Serializing an Inner List (<xref target="ser-innerlis
target="ser-innerlist" format="default"/>) with t"/>) with
(member_value, parameters) to output.</li> (member_value, parameters) to output.</li>
<li>Otherwise, append the result of running Serializing an <li>Otherwise, append the result of running Serializing an
Item (<xref target="ser-item" format="default"/>) with Item (<xref target="ser-item"/>) with
(member_value, parameters) to output.</li> (member_value, parameters) to output.</li>
</ol> </ol>
</li> </li>
<li> <li>
<t>If more members remain in input_dictionary: <t>If more members remain in input_dictionary:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append "," to output.</li> <li>Append "," to output.</li>
<li>Append a single SP to output.</li> <li>Append a single SP to output.</li>
</ol> </ol>
</li> </li>
</ol> </ol>
</li> </li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
<section anchor="ser-item" numbered="true" toc="default"> <section anchor="ser-item">
<name>Serializing an Item</name> <name>Serializing an Item</name>
<t>Given an Item as bare_item and Parameters as item_parameters, <t>Given an Item as bare_item and Parameters as item_parameters,
return an ASCII string suitable for use in a HTTP field value.</t> return an ASCII string suitable for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li>Append the result of running Serializing a Bare Item <xref <li>Append the result of running Serializing a Bare Item (<xref targ
target="ser-bare-item" format="default"/> with bare_item to et="ser-bare-item"/>) with bare_item to
output.</li> output.</li>
<li>Append the result of running Serializing Parameters <xref <li>Append the result of running Serializing Parameters (<xref targe
target="ser-params" format="default"/> with item_parameters to t="ser-params"/>) with item_parameters to
output.</li> output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
<section anchor="ser-bare-item" numbered="true" toc="default"> <section anchor="ser-bare-item">
<name>Serializing a Bare Item</name> <name>Serializing a Bare Item</name>
<t>Given an Item as input_item, return an ASCII string suitable <t>Given an Item as input_item, return an ASCII string suitable
for use in a HTTP field value.</t> for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If input_item is an Integer, return the result of running <li>If input_item is an Integer, return the result of running
Serializing an Integer (<xref target="ser-integer" Serializing an Integer (<xref target="ser-integer"/>) with input_it
format="default"/>) with input_item.</li> em.</li>
<li>If input_item is a Decimal, return the result of running <li>If input_item is a Decimal, return the result of running
Serializing a Decimal (<xref target="ser-decimal" Serializing a Decimal (<xref target="ser-decimal"/>) with input_ite
format="default"/>) with input_item.</li> m.</li>
<li>If input_item is a String, return the result of running <li>If input_item is a String, return the result of running
Serializing a String (<xref target="ser-string" Serializing a String (<xref target="ser-string"/>) with input_item.
format="default"/>) with input_item.</li> </li>
<li>If input_item is a Token, return the result of running <li>If input_item is a Token, return the result of running
Serializing a Token (<xref target="ser-token" Serializing a Token (<xref target="ser-token"/>) with input_item.</
format="default"/>) with input_item.</li> li>
<li>If input_item is a Boolean, return the result of running
Serializing a Boolean (<xref target="ser-boolean"
format="default"/>) with input_item.</li>
<li>If input_item is a Byte Sequence, return the result of <li>If input_item is a Byte Sequence, return the result of
running Serializing a Byte Sequence (<xref target="ser-binary" running Serializing a Byte Sequence (<xref target="ser-binary"/>) w
format="default"/>) with input_item.</li> ith input_item.</li>
<li>Otherwise, fail serialization.</li> <li>Otherwise, fail serialization.</li>
<li>If input_item is a Boolean, return the result of running
Serializing a Boolean (<xref target="ser-boolean"/>) with input_ite
m.</li>
</ol> </ol>
</section> </section>
</section> </section>
<section anchor="ser-integer" numbered="true" toc="default"> <section anchor="ser-integer">
<name>Serializing an Integer</name> <name>Serializing an Integer</name>
<t>Given an Integer as input_integer, return an ASCII string <t>Given an Integer as input_integer, return an ASCII string
suitable for use in a HTTP field value.</t> suitable for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If input_integer is not an integer in the range of <li>If input_integer is not an integer in the range of
-999,999,999,999,999 to 999,999,999,999,999 inclusive, fail -999,999,999,999,999 to 999,999,999,999,999 inclusive, fail
serialization.</li> serialization.</li>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li>If input_integer is less than (but not equal to) 0, append "-" <li>If input_integer is less than (but not equal to) 0, append "-"
to output.</li> to output.</li>
<li>Append input_integer's numeric value represented in base 10 <li>Append input_integer's numeric value represented in base 10
using only decimal digits to output.</li> using only decimal digits to output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
<section anchor="ser-decimal" numbered="true" toc="default"> <section anchor="ser-decimal">
<name>Serializing a Decimal</name> <name>Serializing a Decimal</name>
<t>Given a decimal number as input_decimal, return an ASCII string <t>Given a decimal number as input_decimal, return an ASCII string
suitable for use in a HTTP field value.</t> suitable for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If input_decimal is not a decimal number, fail serialization.</l i> <li>If input_decimal is not a decimal number, fail serialization.</l i>
<li>If input_decimal has more than three significant digits to the <li>If input_decimal has more than three significant digits to the
right of the decimal point, round it to three decimal places, right of the decimal point, round it to three decimal places,
rounding the final digit to the nearest value, or to the even rounding the final digit to the nearest value, or to the even
value if it is equidistant.</li> value if it is equidistant.</li>
<li>If input_decimal has more than 12 significant digits to the <li>If input_decimal has more than 12 significant digits to the
left of the decimal point after rounding, fail serialization.</li> left of the decimal point after rounding, fail serialization.</li>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li>If input_decimal is less than (but not equal to) 0, append "-" <li>If input_decimal is less than (but not equal to) 0, append "-"
to output.</li> to output.</li>
skipping to change at line 871 skipping to change at line 791
"0".</li> "0".</li>
<li>Append "." to output.</li> <li>Append "." to output.</li>
<li>If input_decimal's fractional component is zero, append "0" to <li>If input_decimal's fractional component is zero, append "0" to
output.</li> output.</li>
<li>Otherwise, append the significant digits of input_decimal's <li>Otherwise, append the significant digits of input_decimal's
fractional component represented in base 10 (using only decimal fractional component represented in base 10 (using only decimal
digits) to output.</li> digits) to output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
<section anchor="ser-string" numbered="true" toc="default"> <section anchor="ser-string">
<name>Serializing a String</name> <name>Serializing a String</name>
<t>Given a String as input_string, return an ASCII string suitable <t>Given a String as input_string, return an ASCII string suitable
for use in a HTTP field value.</t> for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Convert input_string into a sequence of ASCII characters; if <li>Convert input_string into a sequence of ASCII characters; if
conversion fails, fail serialization.</li> conversion fails, fail serialization.</li>
<li>If input_string contains characters in the range %x00-1f or <li>If input_string contains characters in the range %x00-1f or
%x7f (i.e., not in VCHAR or SP), fail serialization.</li> %x7f (i.e., not in VCHAR or SP), fail serialization.</li>
<li>Let output be the string DQUOTE.</li> <li>Let output be the string DQUOTE.</li>
<li> <li>
<t>For each character char in input_string: <t>For each character char in input_string:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li> <li>
<t>If char is "\" or DQUOTE: <t>If char is "\" or DQUOTE:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append "\" to output.</li> <li>Append "\" to output.</li>
</ol> </ol>
</li> </li>
<li>Append char to output.</li> <li>Append char to output.</li>
</ol> </ol>
</li> </li>
<li>Append DQUOTE to output.</li> <li>Append DQUOTE to output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
<section anchor="ser-token" numbered="true" toc="default"> <section anchor="ser-token">
<name>Serializing a Token</name> <name>Serializing a Token</name>
<t>Given a Token as input_token, return an ASCII string suitable for <t>Given a Token as input_token, return an ASCII string suitable for
use in a HTTP field value.</t> use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Convert input_token into a sequence of ASCII characters; if <li>Convert input_token into a sequence of ASCII characters; if
conversion fails, fail serialization.</li> conversion fails, fail serialization.</li>
<li>If the first character of input_token is not ALPHA or "*", or <li>If the first character of input_token is not ALPHA or "*", or
the remaining portion contains a character not in tchar, ":" or the remaining portion contains a character not in tchar, ":", or
"/", fail serialization.</li> "/", fail serialization.</li>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li>Append input_token to output.</li> <li>Append input_token to output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
<section anchor="ser-binary" numbered="true" toc="default"> <section anchor="ser-binary">
<name>Serializing a Byte Sequence</name> <name>Serializing a Byte Sequence</name>
<t>Given a Byte Sequence as input_bytes, return an ASCII string <t>Given a Byte Sequence as input_bytes, return an ASCII string
suitable for use in a HTTP field value.</t> suitable for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If input_bytes is not a sequence of bytes, fail serialization.</ li> <li>If input_bytes is not a sequence of bytes, fail serialization.</ li>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li>Append ":" to output.</li> <li>Append ":" to output.</li>
<li>Append the result of base64-encoding input_bytes as per <xref <li>Append the result of base64-encoding input_bytes as per <xref ta
target="RFC4648" sectionFormat="comma" section="4"/>, taking account rget="RFC4648" sectionFormat="comma" section="4"/>, taking account of
of
the requirements below.</li> the requirements below.</li>
<li>Append ":" to output.</li> <li>Append ":" to output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
<t>The encoded data is required to be padded with "=", as per <xref <t>The encoded data is required to be padded with "=", as per <xref ta
target="RFC4648" sectionFormat="comma" section="3.2"/>.</t> rget="RFC4648" sectionFormat="comma" section="3.2"/>.</t>
<t>Likewise, encoded data <bcp14>SHOULD</bcp14> have pad bits set to z ero, as per <t>Likewise, encoded data <bcp14>SHOULD</bcp14> have pad bits set to z ero, as per
<xref target="RFC4648" sectionFormat="comma" section="3.5"/>, unless it is <xref target="RFC4648" sectionFormat="comma" section="3.5"/>, unless it is
not possible to do so due to implementation constraints.</t> not possible to do so due to implementation constraints.</t>
</section> </section>
<section anchor="ser-boolean" numbered="true" toc="default"> <section anchor="ser-boolean">
<name>Serializing a Boolean</name> <name>Serializing a Boolean</name>
<t>Given a Boolean as input_boolean, return an ASCII string suitable <t>Given a Boolean as input_boolean, return an ASCII string suitable
for use in a HTTP field value.</t> for use in an HTTP field value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If input_boolean is not a boolean, fail serialization.</li> <li>If input_boolean is not a boolean, fail serialization.</li>
<li>Let output be an empty string.</li> <li>Let output be an empty string.</li>
<li>Append "?" to output.</li> <li>Append "?" to output.</li>
<li>If input_boolean is true, append "1" to output.</li> <li>If input_boolean is true, append "1" to output.</li>
<li>If input_boolean is false, append "0" to output.</li> <li>If input_boolean is false, append "0" to output.</li>
<li>Return output.</li> <li>Return output.</li>
</ol> </ol>
</section> </section>
</section> </section>
<section anchor="text-parse" numbered="true" toc="default"> <section anchor="text-parse">
<name>Parsing Structured Fields</name> <name>Parsing Structured Fields</name>
<t>When a receiving implementation parses HTTP fields that are known <t>When a receiving implementation parses HTTP fields that are known
to be Structured Fields, it is important that care be taken, as there to be Structured Fields, it is important that care be taken, as there
are a number of edge cases that can cause interoperability or even are a number of edge cases that can cause interoperability or even
security problems. This section specifies the algorithm for doing security problems. This section specifies the algorithm for doing
so.</t> so.</t>
<t>Given an array of bytes input_bytes that represents the chosen <t>Given an array of bytes as input_bytes that represent the chosen
field's field-value (which is empty if that field is not present), and field's field-value (which is empty if that field is not present) and
field_type (one of "dictionary", "list", or "item"), return the parsed field_type (one of "dictionary", "list", or "item"), return the parsed
header value.</t> header value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Convert input_bytes into an ASCII string input_string; if <li>Convert input_bytes into an ASCII string input_string; if
conversion fails, fail parsing.</li> conversion fails, fail parsing.</li>
<li>Discard any leading SP characters from input_string.</li> <li>Discard any leading SP characters from input_string.</li>
<li>If field_type is "list", let output be the result of running <li>If field_type is "list", let output be the result of running
Parsing a List (<xref target="parse-list" format="default"/>) with Parsing a List (<xref target="parse-list"/>) with
input_string.</li> input_string.</li>
<li>If field_type is "dictionary", let output be the result of <li>If field_type is "dictionary", let output be the result of
running Parsing a Dictionary (<xref target="parse-dictionary" running Parsing a Dictionary (<xref target="parse-dictionary"/>) with i
format="default"/>) with input_string.</li> nput_string.</li>
<li>If field_type is "item", let output be the result of running <li>If field_type is "item", let output be the result of running
Parsing an Item (<xref target="parse-item" format="default"/>) with Parsing an Item (<xref target="parse-item"/>) with
input_string.</li> input_string.</li>
<li>Discard any leading SP characters from input_string.</li> <li>Discard any leading SP characters from input_string.</li>
<li>If input_string is not empty, fail parsing.</li> <li>If input_string is not empty, fail parsing.</li>
<li>Otherwise, return output.</li> <li>Otherwise, return output.</li>
</ol> </ol>
<t>When generating input_bytes, parsers <bcp14>MUST</bcp14> combine all field lines <t>When generating input_bytes, parsers <bcp14>MUST</bcp14> combine all field lines
in the same section (header or trailer) that case-insensitively match in the same section (header or trailer) that case-insensitively match
the field name into one comma-separated field-value, as per <xref the field name into one comma-separated field-value, as per <xref target=
target="RFC7230" sectionFormat="comma" section="3.2.2"/>; this assures th "RFC7230" sectionFormat="comma" section="3.2.2"/>; this assures that
at
the entire field value is processed correctly.</t> the entire field value is processed correctly.</t>
<t>For Lists and Dictionaries, this has the effect of correctly <t>For Lists and Dictionaries, this has the effect of correctly
concatenating all of the field's lines, as long as individual members concatenating all of the field's lines, as long as individual members
of the top-level data structure are not split across multiple header of the top-level data structure are not split across multiple header
instances. The parsing algorithms for both types allow tab characters, instances. The parsing algorithms for both types allow tab characters,
since these might be used to combine field lines by some since these might be used to combine field lines by some
implementations.</t> implementations.</t>
<t>Strings split across multiple field lines will have unpredictable <t>Strings split across multiple field lines will have unpredictable
results, because comma(s) and whitespace inserted upon combination results, because one or more commas (with optional whitespace)
will become part of the string output by the parser. Since will become part of the string output by the parser. Since
concatenation might be done by an upstream intermediary, the results concatenation might be done by an upstream intermediary, the results
are not under the control of the serializer or the parser, even when are not under the control of the serializer or the parser, even when
they are both under the control of the same party.</t> they are both under the control of the same party.</t>
<t>Tokens, Integers, Decimals and Byte Sequences cannot be split <t>Tokens, Integers, Decimals, and Byte Sequences cannot be split
across multiple field lines because the inserted commas will cause across multiple field lines because the inserted commas will cause
parsing to fail.</t> parsing to fail.</t>
<t>Parsers <bcp14>MAY</bcp14> fail when processing a field value spread across <t>Parsers <bcp14>MAY</bcp14> fail when processing a field value spread across
multiple field lines, when one of those lines does not parse as that multiple field lines, when one of those lines does not parse as that
field. For example, a parsing handling an Example-String field that's field. For example, a parsing handling an Example-String field that's
defined as a sf-string is allowed to fail when processing this field defined as an sf-string is allowed to fail when processing this field
section:</t> section:</t>
<artwork type="example" name="" align="left" alt=""><![CDATA[ <sourcecode type="http-structured-fields">
Example-String: "foo Example-String: "foo
Example-String: bar" Example-String: bar"
]]></artwork> </sourcecode>
<t>If parsing fails - including when calling another algorithm - the <t>If parsing fails -- including when calling another algorithm -- the
entire field value <bcp14>MUST</bcp14> be ignored (i.e., treated as if th e field were entire field value <bcp14>MUST</bcp14> be ignored (i.e., treated as if th e field were
not present in the section). This is intentionally strict, to improve not present in the section). This is intentionally strict, to improve
interoperability and safety, and specifications referencing this interoperability and safety, and specifications referencing this
document are not allowed to loosen this requirement.</t> document are not allowed to loosen this requirement.</t>
<t>Note that this requirement does not apply to an implementation that <t>Note that this requirement does not apply to an implementation that
is not parsing the field; for example, an intermediary is not required is not parsing the field; for example, an intermediary is not required
to strip a failing field from a message before forwarding it.</t> to strip a failing field from a message before forwarding it.</t>
<section anchor="parse-list" numbered="true" toc="default"> <section anchor="parse-list">
<name>Parsing a List</name> <name>Parsing a List</name>
<t>Given an ASCII string as input_string, return an array of <t>Given an ASCII string as input_string, return an array of
(item_or_inner_list, parameters) tuples. input_string is modified to (item_or_inner_list, parameters) tuples. input_string is modified to
remove the parsed value.</t> remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let members be an empty array.</li> <li>Let members be an empty array.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Append the result of running Parsing an Item or Inner List <li>Append the result of running Parsing an Item or Inner List
(<xref target="parse-item-or-list" format="default"/>) with (<xref target="parse-item-or-list"/>) with
input_string to members.</li> input_string to members.</li>
<li>Discard any leading OWS characters from input_string.</li> <li>Discard any leading OWS characters from input_string.</li>
<li>If input_string is empty, return members.</li> <li>If input_string is empty, return members.</li>
<li>Consume the first character of input_string; if it is not <li>Consume the first character of input_string; if it is not
",", fail parsing.</li> ",", fail parsing.</li>
<li>Discard any leading OWS characters from input_string.</li> <li>Discard any leading OWS characters from input_string.</li>
<li>If input_string is empty, there is a trailing comma; fail pa rsing.</li> <li>If input_string is empty, there is a trailing comma; fail pa rsing.</li>
</ol> </ol>
</li> </li>
<li>No structured data has been found; return members (which is empt y).</li> <li>No structured data has been found; return members (which is empt y).</li>
</ol> </ol>
<section anchor="parse-item-or-list" numbered="true" toc="default"> <section anchor="parse-item-or-list">
<name>Parsing an Item or Inner List</name> <name>Parsing an Item or Inner List</name>
<t>Given an ASCII string as input_string, return the tuple <t>Given an ASCII string as input_string, return the tuple
(item_or_inner_list, parameters), where item_or_inner_list can be (item_or_inner_list, parameters), where item_or_inner_list can be
either a single bare item, or an array of (bare_item, parameters) either a single bare item or an array of (bare_item, parameters)
tuples. input_string is modified to remove the parsed value.</t> tuples. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is "(", return the <li>If the first character of input_string is "(", return the
result of running Parsing an Inner List (<xref result of running Parsing an Inner List (<xref target="parse-innerl
target="parse-innerlist" format="default"/>) with ist"/>) with
input_string.</li> input_string.</li>
<li>Return the result of running Parsing an Item (<xref <li>Return the result of running Parsing an Item (<xref target="pa
target="parse-item" format="default"/>) with input_string.</li> rse-item"/>) with input_string.</li>
</ol> </ol>
</section> </section>
<section anchor="parse-innerlist" numbered="true" toc="default"> <section anchor="parse-innerlist">
<name>Parsing an Inner List</name> <name>Parsing an Inner List</name>
<t>Given an ASCII string as input_string, return the tuple <t>Given an ASCII string as input_string, return the tuple
(inner_list, parameters), where inner_list is an array of (inner_list, parameters), where inner_list is an array of
(bare_item, parameters) tuples. input_string is modified to remove (bare_item, parameters) tuples. input_string is modified to remove
the parsed value.</t> the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Consume the first character of input_string; if it is not <li>Consume the first character of input_string; if it is not
"(", fail parsing.</li> "(", fail parsing.</li>
<li>Let inner_list be an empty array.</li> <li>Let inner_list be an empty array.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Discard any leading SP characters from input_string.</li> <li>Discard any leading SP characters from input_string.</li>
<li> <li>
<t>If the first character of input_string is ")": <t>If the first character of input_string is ")":
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Consume the first character of input_string.</li> <li>Consume the first character of input_string.</li>
<li>Let parameters be the result of running Parsing <li>Let parameters be the result of running Parsing
Parameters (<xref target="parse-param" Parameters (<xref target="parse-param"/>) with input_string
format="default"/>) with input_string.</li> .</li>
<li>Return the tuple (inner_list, parameters).</li> <li>Return the tuple (inner_list, parameters).</li>
</ol> </ol>
</li> </li>
<li>Let item be the result of running Parsing an Item (<xref <li>Let item be the result of running Parsing an Item (<xref t
target="parse-item" format="default"/>) with arget="parse-item"/>) with
input_string.</li> input_string.</li>
<li>Append item to inner_list.</li> <li>Append item to inner_list.</li>
<li>If the first character of input_string is not SP or ")", <li>If the first character of input_string is not SP or ")",
fail parsing.</li> fail parsing.</li>
</ol> </ol>
</li> </li>
<li>The end of the inner list was not found; fail parsing.</li> <li>The end of the Inner List was not found; fail parsing.</li>
</ol> </ol>
</section> </section>
</section> </section>
<section anchor="parse-dictionary" numbered="true" toc="default"> <section anchor="parse-dictionary">
<name>Parsing a Dictionary</name> <name>Parsing a Dictionary</name>
<t>Given an ASCII string as input_string, return an ordered map <t>Given an ASCII string as input_string, return an ordered map
whose values are (item_or_inner_list, parameters) whose values are (item_or_inner_list, parameters)
tuples. input_string is modified to remove the parsed value.</t> tuples. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let dictionary be an empty, ordered map.</li> <li>Let dictionary be an empty, ordered map.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Let this_key be the result of running Parsing a Key (<xref <li>Let this_key be the result of running Parsing a Key (<xref t
target="parse-key" format="default"/>) with input_string.</li> arget="parse-key"/>) with input_string.</li>
<li> <li>
<t>If the first character of input_string is "=": <t>If the first character of input_string is "=":
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Consume the first character of input_string.</li> <li>Consume the first character of input_string.</li>
<li>Let member be the result of running Parsing an Item or <li>Let member be the result of running Parsing an Item or
Inner List (<xref target="parse-item-or-list" Inner List (<xref target="parse-item-or-list"/>) with input_s
format="default"/>) with input_string.</li> tring.</li>
</ol> </ol>
</li> </li>
<li> <li>
<t>Otherwise: <t>Otherwise:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Let value be Boolean true.</li> <li>Let value be Boolean true.</li>
<li>Let parameters be the result of running Parsing <li>Let parameters be the result of running Parsing
Parameters <xref target="parse-param" format="default"/> Parameters (<xref target="parse-param"/>)
with input_string.</li> with input_string.</li>
<li>Let member be the tuple (value, parameters).</li> <li>Let member be the tuple (value, parameters).</li>
</ol> </ol>
</li> </li>
<li>Add name this_key with value member to dictionary. If <li>Add name this_key with value member to dictionary. If
dictionary already contains a name this_key (comparing dictionary already contains a name this_key (comparing
character-for-character), overwrite its value.</li> character for character), overwrite its value.</li>
<li>Discard any leading OWS characters from input_string.</li> <li>Discard any leading OWS characters from input_string.</li>
<li>If input_string is empty, return dictionary.</li> <li>If input_string is empty, return dictionary.</li>
<li>Consume the first character of input_string; if it is not <li>Consume the first character of input_string; if it is not
",", fail parsing.</li> ",", fail parsing.</li>
<li>Discard any leading OWS characters from input_string.</li> <li>Discard any leading OWS characters from input_string.</li>
<li>If input_string is empty, there is a trailing comma; fail pa rsing.</li> <li>If input_string is empty, there is a trailing comma; fail pa rsing.</li>
</ol> </ol>
</li> </li>
<li>No structured data has been found; return dictionary (which is e mpty).</li> <li>No structured data has been found; return dictionary (which is e mpty).</li>
</ol> </ol>
<t>Note that when duplicate Dictionary keys are encountered, this <t>Note that when duplicate Dictionary keys are encountered, all but
has the effect of ignoring all but the last instance.</t> the last instance are ignored.</t>
</section> </section>
<section anchor="parse-item" numbered="true" toc="default"> <section anchor="parse-item">
<name>Parsing an Item</name> <name>Parsing an Item</name>
<t>Given an ASCII string as input_string, return a (bare_item, <t>Given an ASCII string as input_string, return a (bare_item,
parameters) tuple. input_string is modified to remove the parsed parameters) tuple. input_string is modified to remove the parsed
value.</t> value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let bare_item be the result of running Parsing a Bare Item <li>Let bare_item be the result of running Parsing a Bare Item
(<xref target="parse-bare-item" format="default"/>) with (<xref target="parse-bare-item"/>) with
input_string.</li> input_string.</li>
<li>Let parameters be the result of running Parsing Parameters <li>Let parameters be the result of running Parsing Parameters
(<xref target="parse-param" format="default"/>) with (<xref target="parse-param"/>) with
input_string.</li> input_string.</li>
<li>Return the tuple (bare_item, parameters).</li> <li>Return the tuple (bare_item, parameters).</li>
</ol> </ol>
<section anchor="parse-bare-item" numbered="true" toc="default"> <section anchor="parse-bare-item">
<name>Parsing a Bare Item</name> <name>Parsing a Bare Item</name>
<t>Given an ASCII string as input_string, return a bare <t>Given an ASCII string as input_string, return a bare
Item. input_string is modified to remove the parsed value.</t> Item. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <!--[rfced] Would you like to move #5 up in the list so that the
section mentions will be in ascending order?
Original:
2. If the first character of input_string is a DQUOTE, return the
result of running Parsing a String (Section 4.2.5) with
input_string.
3. If the first character of input_string is ":", return the result
of running Parsing a Byte Sequence (Section 4.2.7) with
input_string.
4. If the first character of input_string is "?", return the result
of running Parsing a Boolean (Section 4.2.8) with input_string.
5. If the first character of input_string is an ALPHA or "*", return
the result of running Parsing a Token (Section 4.2.6) with
input_string.
Perhaps:
2. If the first character of input_string is a DQUOTE, return the
result of running Parsing a String (Section 4.2.5) with
input_string.
3. If the first character of input_string is an ALPHA or "*", return
the result of running Parsing a Token (Section 4.2.6) with
input_string.
4. If the first character of input_string is ":", return the result
of running Parsing a Byte Sequence (Section 4.2.7) with
input_string.
5. If the first character of input_string is "?", return the result
of running Parsing a Boolean (Section 4.2.8) with input_string.
-->
<ol>
<li>If the first character of input_string is a "-" or a DIGIT, <li>If the first character of input_string is a "-" or a DIGIT,
return the result of running Parsing an Integer or Decimal return the result of running Parsing an Integer or Decimal
(<xref target="parse-number" format="default"/>) with (<xref target="parse-number"/>) with
input_string.</li> input_string.</li>
<li>If the first character of input_string is a DQUOTE, return <li>If the first character of input_string is a DQUOTE, return
the result of running Parsing a String (<xref the result of running Parsing a String (<xref target="parse-string"
target="parse-string" format="default"/>) with />) with
input_string.</li> input_string.</li>
<li>If the first character of input_string is an ALPHA or "*",
return the result of running Parsing a Token (<xref target="parse-t
oken"/>) with input_string.</li>
<li>If the first character of input_string is ":", return the <li>If the first character of input_string is ":", return the
result of running Parsing a Byte Sequence (<xref result of running Parsing a Byte Sequence (<xref target="parse-bina
target="parse-binary" format="default"/>) with ry"/>) with
input_string.</li> input_string.</li>
<li>If the first character of input_string is "?", return the <li>If the first character of input_string is "?", return the
result of running Parsing a Boolean (<xref result of running Parsing a Boolean (<xref target="parse-boolean"/>
target="parse-boolean" format="default"/>) with ) with
input_string.</li> input_string.</li>
<li>If the first character of input_string is an ALPHA or "*",
return the result of running Parsing a Token (<xref
target="parse-token" format="default"/>) with input_string.</li>
<li>Otherwise, the item type is unrecognized; fail parsing.</li> <li>Otherwise, the item type is unrecognized; fail parsing.</li>
</ol> </ol>
</section> </section>
<section anchor="parse-param" numbered="true" toc="default"> <section anchor="parse-param">
<name>Parsing Parameters</name> <name>Parsing Parameters</name>
<t>Given an ASCII string as input_string, return an ordered map <t>Given an ASCII string as input_string, return an ordered map
whose values are bare Items. input_string is modified to remove whose values are bare Items. input_string is modified to remove
the parsed value.</t> the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let parameters be an empty, ordered map.</li> <li>Let parameters be an empty, ordered map.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is not ";", exit th e loop.</li> <li>If the first character of input_string is not ";", exit th e loop.</li>
<li>Consume a ";" character from the beginning of input_string .</li> <li>Consume a ";" character from the beginning of input_string .</li>
<li>Discard any leading SP characters from input_string.</li> <li>Discard any leading SP characters from input_string.</li>
<li>let param_name be the result of running Parsing a Key <li>Let param_name be the result of running Parsing a Key
(<xref target="parse-key" format="default"/>) with (<xref target="parse-key"/>) with
input_string.</li> input_string.</li>
<li>Let param_value be Boolean true.</li> <li>Let param_value be Boolean true.</li>
<li> <li>
<t>If the first character of input_string is "=": <t>If the first character of input_string is "=":
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Consume the "=" character at the beginning of input_st ring.</li> <li>Consume the "=" character at the beginning of input_st ring.</li>
<li>Let param_value be the result of running Parsing a <li>Let param_value be the result of running Parsing a
Bare Item (<xref target="parse-bare-item" Bare Item (<xref target="parse-bare-item"/>) with input_str
format="default"/>) with input_string.</li> ing.</li>
</ol> </ol>
</li> </li>
<li>Append key param_name with value param_value to <li>Append key param_name with value param_value to
parameters. If parameters already contains a name param_name parameters. If parameters already contains a name param_name
(comparing character-for-character), overwrite its (comparing character for character), overwrite its
value.</li> value.</li>
</ol> </ol>
</li> </li>
<li>Return parameters.</li> <li>Return parameters.</li>
</ol> </ol>
<t>Note that when duplicate Parameter keys are encountered, this <t>Note that when duplicate parameter keys are encountered,
has the effect of ignoring all but the last instance.</t> all but the last instance are ignored.</t>
</section> </section>
<section anchor="parse-key" numbered="true" toc="default"> <section anchor="parse-key">
<name>Parsing a Key</name> <name>Parsing a Key</name>
<t>Given an ASCII string as input_string, return a <t>Given an ASCII string as input_string, return a
key. input_string is modified to remove the parsed value.</t> key. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is not lcalpha or <li>If the first character of input_string is not lcalpha or
"*", fail parsing.</li> "*", fail parsing.</li>
<li>Let output_string be an empty string.</li> <li>Let output_string be an empty string.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is not one of <li>If the first character of input_string is not one of
lcalpha, DIGIT, "_", "-", ".", or "*", return lcalpha, DIGIT, "_", "-", ".", or "*", return
output_string.</li> output_string.</li>
<li>Let char be the result of consuming the first character of input_string.</li> <li>Let char be the result of consuming the first character of input_string.</li>
<li>Append char to output_string.</li> <li>Append char to output_string.</li>
</ol> </ol>
</li> </li>
<li>Return output_string.</li> <li>Return output_string.</li>
</ol> </ol>
</section> </section>
</section> </section>
<section anchor="parse-number" numbered="true" toc="default"> <section anchor="parse-number">
<name>Parsing an Integer or Decimal</name> <name>Parsing an Integer or Decimal</name>
<t>Given an ASCII string as input_string, return an Integer or <t>Given an ASCII string as input_string, return an Integer or
Decimal. input_string is modified to remove the parsed value.</t> Decimal. input_string is modified to remove the parsed value.</t>
<t>NOTE: This algorithm parses both Integers (<xref target="integer" <t>NOTE: This algorithm parses both Integers (<xref target="integer"/>
format="default"/>) and Decimals (<xref target="decimal" ) and Decimals (<xref target="decimal"/>) and returns the corresponding structur
format="default"/>), and returns the corresponding structure.</t> e.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let type be "integer".</li> <li>Let type be "integer".</li>
<li>Let sign be 1.</li> <li>Let sign be 1.</li>
<li>Let input_number be an empty string.</li> <li>Let input_number be an empty string.</li>
<li>If the first character of input_string is "-", consume it and <li>If the first character of input_string is "-", consume it and
set sign to -1.</li> set sign to -1.</li>
<li>If input_string is empty, there is an empty integer; fail <li>If input_string is empty, there is an empty integer; fail
parsing.</li> parsing.</li>
<li>If the first character of input_string is not a DIGIT, fail <li>If the first character of input_string is not a DIGIT, fail
parsing.</li> parsing.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Let char be the result of consuming the first character of <li>Let char be the result of consuming the first character of
input_string.</li> input_string.</li>
<li>If char is a DIGIT, append it to input_number.</li> <li>If char is a DIGIT, append it to input_number.</li>
<li> <li>
<t>Else, if type is "integer" and char is ".": <t>Else, if type is "integer" and char is ".":
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>If input_number contains more than 12 characters, fail p arsing.</li> <li>If input_number contains more than 12 characters, fail p arsing.</li>
<li>Otherwise, append char to input_number and set type to " decimal".</li> <li>Otherwise, append char to input_number and set type to " decimal".</li>
</ol> </ol>
</li> </li>
<li>Otherwise, prepend char to input_string, and exit the loop.< /li> <li>Otherwise, prepend char to input_string, and exit the loop.< /li>
<li>If type is "integer" and input_number contains more than <li>If type is "integer" and input_number contains more than
15 characters, fail parsing.</li> 15 characters, fail parsing.</li>
<li>If type is "decimal" and input_number contains more than <li>If type is "decimal" and input_number contains more than
16 characters, fail parsing.</li> 16 characters, fail parsing.</li>
</ol> </ol>
</li> </li>
<li> <li>
<t>If type is "integer": <t>If type is "integer":
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Parse input_number as an integer and let output_number be <li>Parse input_number as an integer and let output_number be
the product of the result and sign.</li> the product of the result and sign.</li>
<li>If output_number is outside the range -999,999,999,999,999 <li>If output_number is outside the range -999,999,999,999,999
to 999,999,999,999,999 inclusive, fail parsing.</li> to 999,999,999,999,999 inclusive, fail parsing.</li>
</ol> </ol>
</li> </li>
<li> <li>
<t>Otherwise: <t>Otherwise:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>If the final character of input_number is ".", fail parsing. </li> <li>If the final character of input_number is ".", fail parsing. </li>
<li>If the number of characters after "." in input_number is <li>If the number of characters after "." in input_number is
greater than three, fail parsing.</li> greater than three, fail parsing.</li>
<li>Parse input_number as a decimal number and let <li>Parse input_number as a decimal number and let
output_number be the product of the result and sign.</li> output_number be the product of the result and sign.</li>
</ol> </ol>
</li> </li>
<li>Return output_number.</li> <li>Return output_number.</li>
</ol> </ol>
</section> </section>
<section anchor="parse-string" numbered="true" toc="default"> <section anchor="parse-string">
<name>Parsing a String</name> <name>Parsing a String</name>
<t>Given an ASCII string as input_string, return an unquoted <t>Given an ASCII string as input_string, return an unquoted
String. input_string is modified to remove the parsed value.</t> String. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>Let output_string be an empty string.</li> <li>Let output_string be an empty string.</li>
<li>If the first character of input_string is not DQUOTE, fail parsi ng.</li> <li>If the first character of input_string is not DQUOTE, fail parsi ng.</li>
<li>Discard the first character of input_string.</li> <li>Discard the first character of input_string.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>Let char be the result of consuming the first character of i nput_string.</li> <li>Let char be the result of consuming the first character of i nput_string.</li>
<li> <li>
<t>If char is a backslash ("\"): <t>If char is a backslash ("\"):
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>If input_string is now empty, fail parsing.</li> <li>If input_string is now empty, fail parsing.</li>
<li>Let next_char be the result of consuming the first <li>Let next_char be the result of consuming the first
character of input_string.</li> character of input_string.</li>
<li>If next_char is not DQUOTE or "\", fail parsing.</li> <li>If next_char is not DQUOTE or "\", fail parsing.</li>
<li>Append next_char to output_string.</li> <li>Append next_char to output_string.</li>
</ol> </ol>
</li> </li>
<li>Else, if char is DQUOTE, return output_string.</li> <li>Else, if char is DQUOTE, return output_string.</li>
<li>Else, if char is in the range %x00-1f or %x7f (i.e., is <li>Else, if char is in the range %x00-1f or %x7f (i.e., it's
not in VCHAR or SP), fail parsing.</li> not in VCHAR or SP), fail parsing.</li>
<li>Else, append char to output_string.</li> <li>Else, append char to output_string.</li>
</ol> </ol>
</li> </li>
<li>Reached the end of input_string without finding a closing <li>Reached the end of input_string without finding a closing
DQUOTE; fail parsing.</li> DQUOTE; fail parsing.</li>
</ol> </ol>
</section> </section>
<section anchor="parse-token" numbered="true" toc="default"> <section anchor="parse-token">
<name>Parsing a Token</name> <name>Parsing a Token</name>
<t>Given an ASCII string as input_string, return a <t>Given an ASCII string as input_string, return a
Token. input_string is modified to remove the parsed value.</t> Token. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is not ALPHA or "*", <li>If the first character of input_string is not ALPHA or "*",
fail parsing.</li> fail parsing.</li>
<li>Let output_string be an empty string.</li> <li>Let output_string be an empty string.</li>
<li> <li>
<t>While input_string is not empty: <t>While input_string is not empty:
</t> </t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is not in tchar, <li>If the first character of input_string is not in tchar,
":" or "/", return output_string.</li> ":", or "/", return output_string.</li>
<li>Let char be the result of consuming the first character of <li>Let char be the result of consuming the first character of
input_string.</li> input_string.</li>
<li>Append char to output_string.</li> <li>Append char to output_string.</li>
</ol> </ol>
</li> </li>
<li>Return output_string.</li> <li>Return output_string.</li>
</ol> </ol>
</section> </section>
<section anchor="parse-binary" numbered="true" toc="default"> <section anchor="parse-binary">
<name>Parsing a Byte Sequence</name> <name>Parsing a Byte Sequence</name>
<t>Given an ASCII string as input_string, return a Byte <t>Given an ASCII string as input_string, return a Byte
Sequence. input_string is modified to remove the parsed value.</t> Sequence. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is not ":", fail parsing. </li> <li>If the first character of input_string is not ":", fail parsing. </li>
<li>Discard the first character of input_string.</li> <li>Discard the first character of input_string.</li>
<li>If there is not a ":" character before the end of input_string, fail parsing.</li> <li>If there is not a ":" character before the end of input_string, fail parsing.</li>
<li>Let b64_content be the result of consuming content of <li>Let b64_content be the result of consuming content of
input_string up to but not including the first instance of the input_string up to but not including the first instance of the
character ":".</li> character ":".</li>
<li>Consume the ":" character at the beginning of input_string.</li> <li>Consume the ":" character at the beginning of input_string.</li>
<li>If b64_content contains a character not included in ALPHA, <li>If b64_content contains a character not included in ALPHA,
DIGIT, "+", "/" and "=", fail parsing.</li> DIGIT, "+", "/", and "=", fail parsing.</li>
<li>Let binary_content be the result of Base 64 Decoding <xref <li>Let binary_content be the result of base64-decoding <xref target
target="RFC4648" format="default"/> b64_content, synthesizing ="RFC4648"/> b64_content, synthesizing
padding if necessary (note the requirements about recipient padding if necessary (note the requirements about recipient
behavior below).</li> behavior below).</li>
<li>Return binary_content.</li> <li>Return binary_content.</li>
</ol> </ol>
<t>Because some implementations of base64 do not allow rejection of <t>Because some implementations of base64 do not allow rejection of
encoded data that is not properly "=" padded (see <xref encoded data that is not properly "=" padded (see <xref target="RFC4648
target="RFC4648" sectionFormat="comma" section="3.2"/>), parsers <bcp14 " sectionFormat="comma" section="3.2"/>), parsers <bcp14>SHOULD
>SHOULD
NOT</bcp14> fail when "=" padding is not present, unless they cannot be NOT</bcp14> fail when "=" padding is not present, unless they cannot be
configured to do so.</t> configured to do so.</t>
<t>Because some implementations of base64 do not allow rejection of <t>Because some implementations of base64 do not allow rejection of
encoded data that has non-zero pad bits (see <xref target="RFC4648" encoded data that has non-zero pad bits (see <xref target="RFC4648" sec
sectionFormat="comma" section="3.5"/>), parsers <bcp14>SHOULD NOT</bcp1 tionFormat="comma" section="3.5"/>), parsers <bcp14>SHOULD NOT</bcp14> fail when
4> fail when
non-zero pad bits are present, unless they cannot be configured to non-zero pad bits are present, unless they cannot be configured to
do so.</t> do so.</t>
<t>This specification does not relax the requirements in <xref <t>This specification does not relax the requirements in <xref target=
target="RFC4648"/>, Sections <xref "RFC4648"/>, Sections <xref target="RFC4648" sectionFormat="bare" section="3.1"/
target="RFC4648" sectionFormat="bare" section="3.1"/> and <xref > and <xref target="RFC4648" sectionFormat="bare" section="3.3"/>; therefore,
target="RFC4648" sectionFormat="bare" section="3.3"/>; therefore, parsers <bcp14>MUST</bcp14> fail on characters outside the base64 alpha
parsers <bcp14>MUST</bcp14> fail on characters outside the base64 alpha bet and on line
bet, and on feeds in encoded data.</t>
line feeds in encoded data.</t>
</section> </section>
<section anchor="parse-boolean" numbered="true" toc="default"> <section anchor="parse-boolean">
<name>Parsing a Boolean</name> <name>Parsing a Boolean</name>
<t>Given an ASCII string as input_string, return a <t>Given an ASCII string as input_string, return a
Boolean. input_string is modified to remove the parsed value.</t> Boolean. input_string is modified to remove the parsed value.</t>
<ol spacing="normal" type="1"> <ol>
<li>If the first character of input_string is not "?", fail parsing. </li> <li>If the first character of input_string is not "?", fail parsing. </li>
<li>Discard the first character of input_string.</li> <li>Discard the first character of input_string.</li>
<li>If the first character of input_string matches "1", discard <li>If the first character of input_string matches "1", discard
the first character, and return true.</li> the first character, and return true.</li>
<li>If the first character of input_string matches "0", discard <li>If the first character of input_string matches "0", discard
the first character, and return false.</li> the first character, and return false.</li>
<li>No value has matched; fail parsing.</li> <li>If no value has matched; fail parsing.</li>
</ol> </ol>
</section> </section>
</section> </section>
</section> </section>
<section anchor="iana-considerations" numbered="true" toc="default"> <section anchor="iana-considerations">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t>This document has no actions for IANA.</t> <t>This document has no IANA actions.</t>
</section> </section>
<section anchor="security-considerations" numbered="true" toc="default"> <section anchor="security-considerations">
<name>Security Considerations</name> <name>Security Considerations</name>
<t>The size of most types defined by Structured Fields is not limited; <t>The size of most types defined by Structured Fields is not limited;
as a result, extremely large fields could be an attack vector (e.g., for as a result, extremely large fields could be an attack vector (e.g., for
resource consumption). Most HTTP implementations limit the sizes of resource consumption). Most HTTP implementations limit the sizes of
individual fields as well as the overall header or trailer section size individual fields as well as the overall header or trailer section size
to mitigate such attacks.</t> to mitigate such attacks.</t>
<t>It is possible for parties with the ability to inject new HTTP fields <t>It is possible for parties with the ability to inject new HTTP fields
to change the meaning of a Structured Field. In some circumstances, this to change the meaning of a Structured Field. In some circumstances, this
will cause parsing to fail, but it is not possible to reliably fail in will cause parsing to fail, but it is not possible to reliably fail in
all such circumstances.</t> all such circumstances.</t>
</section> </section>
</middle> </middle>
<back> <back>
<displayreference target="RFC3629" to="UTF-8"/>
<displayreference target="RFC3629" to="UTF-8"/>
<references> <references>
<name>References</name> <name>References</name>
<references> <references>
<name>Normative References</name> <name>Normative References</name>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7230.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7230.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.2119.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.2119.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.8174.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.8174.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.5234.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.5234.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.0020.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.0020.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.4648.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.4648.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refere
nce.RFC.3986.xml"/>
<!--[rfced] RFC 3986 had no corresponding reference entry in the References
section. We have listed it as a normative reference. Please let us know of any
objections.
</references> </references>
<references> <references>
<name>Informative References</name> <name>Informative References</name>
<!-- [rfced] [IEEE754] The URL below is correct. DOI https://doi.org/10.1109/IEE
ESTD.2019.8766229 -->
<reference anchor="IEEE754" target="https://ieeexplore.ieee.org/document /8766229"> <reference anchor="IEEE754" target="https://ieeexplore.ieee.org/document /8766229">
<front> <front>
<title>IEEE Standard for Floating-Point Arithmetic</title> <title>IEEE Standard for Floating-Point Arithmetic</title>
<seriesInfo name="ISBN" value="978-1-5044-5924-2"/>
<seriesInfo name="DOI" value="10.1109/IEEESTD.2019.8766229"/> <seriesInfo name="DOI" value="10.1109/IEEESTD.2019.8766229"/>
<seriesInfo name="IEEE" value="754-2019"/> <seriesInfo name="IEEE" value="754-2019"/>
<author> <author>
<organization>IEEE</organization> <organization>IEEE</organization>
</author> </author>
<date year="2019" month="July"/> <date year="2019" month="July"/>
</front> </front>
</reference> </reference>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.3629.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.3629.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7231.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7231.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7540.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7540.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7541.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7541.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.8259.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.8259.xml"/>
<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7493.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/refer ence.RFC.7493.xml"/>
</references> </references>
</references> </references>
<section anchor="faq" numbered="true" toc="default"> <section anchor="faq">
<name>Frequently Asked Questions</name> <name>Frequently Asked Questions</name>
<section anchor="why-not-json" numbered="true" toc="default"> <section anchor="why-not-json">
<name>Why not JSON?</name> <name>Why Not JSON?</name>
<t>Earlier proposals for Structured Fields were based upon JSON <xref <t>Earlier proposals for Structured Fields were based upon JSON <xref ta
target="RFC8259" format="default"/>. However, constraining its use to rget="RFC8259"/>. However, constraining its use to
make it suitable for HTTP header fields required senders and make it suitable for HTTP header fields required senders and
recipients to implement specific additional handling.</t> recipients to implement specific additional handling.</t>
<t>For example, JSON has specification issues around large numbers and <t>For example, JSON has specification issues around large numbers and
objects with duplicate members. Although advice for avoiding these objects with duplicate members. Although advice for avoiding these
issues is available (e.g., <xref target="RFC7493" format="default"/>), issues is available (e.g., <xref target="RFC7493"/>),
it cannot be relied upon.</t> it cannot be relied upon.</t>
<t>Likewise, JSON strings are by default Unicode strings, which have a <t>Likewise, JSON strings are by default Unicode strings, which have a
number of potential interoperability issues (e.g., in number of potential interoperability issues (e.g., in
comparison). Although implementers can be advised to avoid non-ASCII comparison). Although implementers can be advised to avoid non-ASCII
content where unnecessary, this is difficult to enforce.</t> content where unnecessary, this is difficult to enforce.</t>
<t>Another example is JSON's ability to nest content to arbitrary <t>Another example is JSON's ability to nest content to arbitrary
depths. Since the resulting memory commitment might be unsuitable depths. Since the resulting memory commitment might be unsuitable
(e.g., in embedded and other limited server deployments), it's (e.g., in embedded and other limited server deployments), it's
necessary to limit it in some fashion; however, existing JSON necessary to limit it in some fashion; however, existing JSON
implementations have no such limits, and even if a limit is specified, implementations have no such limits, and even if a limit is specified,
it's likely that some field definition will find a need to violate it's likely that some field definition will find a need to violate
it.</t> it.</t>
<t>Because of JSON's broad adoption and implementation, it is <t>Because of JSON's broad adoption and implementation, it is
difficult to impose such additional constraints across all difficult to impose such additional constraints across all
implementations; some deployments would fail to enforce them, thereby implementations; some deployments would fail to enforce them, thereby
harming interoperability. In short, if it looks like JSON, people will harming interoperability. In short, if it looks like JSON, people will
be tempted to use a JSON parser / serializer on field values.</t> be tempted to use a JSON parser/serializer on field values.</t>
<t>Since a major goal for Structured Fields is to improve <t>Since a major goal for Structured Fields is to improve
interoperability and simplify implementation, these concerns led to a interoperability and simplify implementation, these concerns led to a
format that requires a dedicated parser and serializer.</t> format that requires a dedicated parser and serializer.</t>
<t>Additionally, there were widely shared feelings that JSON doesn't <t>Additionally, there were widely shared feelings that JSON doesn't
"look right" in HTTP fields.</t> "look right" in HTTP fields.</t>
</section> </section>
</section> </section>
<section anchor="implementation-notes" numbered="true" toc="default"> <section anchor="implementation-notes">
<name>Implementation Notes</name> <name>Implementation Notes</name>
<t>A generic implementation of this specification should expose the <t>A generic implementation of this specification should expose the
top-level serialize (<xref target="text-serialize" format="default"/>) top-level serialize (<xref target="text-serialize"/>)
and parse (<xref target="text-parse" format="default"/>) functions. They and parse (<xref target="text-parse"/>) functions. They
need not be functions; for example, it could be implemented as an need not be functions; for example, it could be implemented as an
object, with methods for each of the different top-level types.</t> object, with methods for each of the different top-level types.</t>
<t>For interoperability, it's important that generic implementations be <t>For interoperability, it's important that generic implementations be
complete and follow the algorithms closely; see <xref target="strict" complete and follow the algorithms closely; see <xref target="strict"/>. T
format="default"/>. To aid this, a common test suite is being maintained o aid this, a common test suite is being maintained
by the community at <eref by the community at <eref brackets="angle" target="https://github.com/http
target="https://github.com/httpwg/structured-field-tests">https://github.c wg/structured-field-tests"/>.</t>
om/httpwg/structured-field-tests</eref>.</t>
<t>Implementers should note that Dictionaries and Parameters are <t>Implementers should note that Dictionaries and Parameters are
order-preserving maps. Some fields may not convey meaning in the order-preserving maps. Some fields may not convey meaning in the
ordering of these data types, but it should still be exposed so that ordering of these data types, but it should still be exposed so
applications which need to use it will have it available.</t> that it will be available to applications that need to use it.</t>
<t>Likewise, implementations should note that it's important to preserve <t>Likewise, implementations should note that it's important to preserve
the distinction between Tokens and Strings. While most programming the distinction between Tokens and Strings. While most programming
languages have native types that map to the other types well, it may be languages have native types that map to the other types well, it may be
necessary to create a wrapper "token" object or use a parameter on necessary to create a wrapper "token" object or use a parameter on
functions to assure that these types remain separate.</t> functions to assure that these types remain separate.</t>
<t>The serialization algorithm is defined in a way that it is not <t>The serialization algorithm is defined in a way that it is not
strictly limited to the data types defined in <xref target="types" strictly limited to the data types defined in <xref target="types"/> in ev
format="default"/> in every case. For example, Decimals are designed to ery case. For example, Decimals are designed to
take broader input and round to allowed values.</t> take broader input and round to allowed values.</t>
<t>Implementations are allowed to limit the allowed size of different <t>Implementations are allowed to limit the size of different
structures, subject to the minimums defined for each type. When a structures, subject to the minimums defined for each type. When a
structure exceeds an implementation limit, that structure fails parsing structure exceeds an implementation limit, that structure fails parsing
or serialisation.</t> or serialization.</t>
</section>
<section anchor="changes" numbered="true" toc="default">
<name>Changes</name>
<t><em>RFC Editor: Please remove this section before publication.</em></t>
<section anchor="since-draft-ietf-httpbis-header-structure-18" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-18</name>
<ul spacing="normal">
<li>Use "sf-" prefix for ABNF, not "sh-".</li>
<li>Fix indentation in Dictionary serialisation (#1164).</li>
<li>Add example for Token; tweak example field names (#1147).</li>
<li>Editorial improvements.</li>
<li>Note that exceeding implementation limits implies failure.</li>
<li>Talk about specifying order of Dictionary members and
Parameters, not cardinality.</li>
<li>Allow (but don't require) parsers to fail when a single field
line isn't valid.</li>
<li>Note that some aspects of Integers and Decimals are not
necessarily preserved.</li>
<li>Allow Lists and Dictionaries to be delimited by OWS, rather than
*SP, to make parsing more robust.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-17" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-17</name>
<ul spacing="normal">
<li>Editorial improvements.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-16" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-16</name>
<ul spacing="normal">
<li>Editorial improvements.</li>
<li>Discussion on forwards compatibility.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-15" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-15</name>
<ul spacing="normal">
<li>Editorial improvements.</li>
<li>Use HTTP field terminology more consistently, in line with
recent changes to HTTP-core.</li>
<li>String length requirements apply to decoded strings (#1051).</li>
<li>Correctly round decimals in serialisation (#1043).</li>
<li>Clarify input to serialisation algorithms (#1055).</li>
<li>Omitted True dictionary value can have parameters (#1083).</li>
<li>Keys can now start with '*' (#1068).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-14" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-14</name>
<ul spacing="normal">
<li>Editorial improvements.</li>
<li>Allow empty dictionary values (#992).</li>
<li>Change value of omitted parameter value to True (#995).</li>
<li>Explain more about splitting dictionaries and lists across
header instances (#997).</li>
<li>Disallow HTAB, replace OWS with spaces (#998).</li>
<li>Change byte sequence delimiters from "*" to ":" (#991).</li>
<li>Allow tokens to start with "*" (#991).</li>
<li>Change Floats to fixed-precision Decimals (#982).</li>
<li>Round the fractional component of decimal, rather than
truncating it (#982).</li>
<li>Handle duplicate dictionary and parameter keys by overwriting
their values, rather than failing (#997).</li>
<li>Allow "." in key (#1027).</li>
<li>Check first character of key in serialisation (#1037).</li>
<li>Talk about greasing headers (#1015).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-13" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-13</name>
<ul spacing="normal">
<li>Editorial improvements.</li>
<li>Define "structured header name" and "structured header value"
terms (#908).</li>
<li>Corrected text about valid characters in strings (#931).</li>
<li>Removed most instances of the word "textual", as it was
redundant (#915).</li>
<li>Allowed parameters on Items and Inner Lists (#907).</li>
<li>Expand the range of characters in token (#961).</li>
<li>Disallow OWS before ";" delimiter in parameters (#961).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-12" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-12</name>
<ul spacing="normal">
<li>Editorial improvements.</li>
<li>Reworked float serialisation (#896).</li>
<li>Don't add a trailing space in inner-list (#904).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-11" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-11</name>
<ul spacing="normal">
<li>Allow * in key (#844).</li>
<li>Constrain floats to six digits of precision (#848).</li>
<li>Allow dictionary members to have parameters (#842).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-10" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-10</name>
<ul spacing="normal">
<li>Update abstract (#799).</li>
<li>Input and output are now arrays of bytes (#662).</li>
<li>Implementations need to preserve difference between token and
string (#790).</li>
<li>Allow empty dictionaries and lists (#781).</li>
<li>Change parameterized lists to have primary items (#797).</li>
<li>Allow inner lists in both dictionaries and lists; removes lists
of lists (#816).</li>
<li>Subsume Parameterised Lists into Lists (#839).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-09" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-09</name>
<ul spacing="normal">
<li>Changed Boolean from T/F to 1/0 (#784).</li>
<li>Parameters are now ordered maps (#765).</li>
<li>Clamp integers to 15 digits (#737).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-08" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-08</name>
<ul spacing="normal">
<li>Disallow whitespace before items properly (#703).</li>
<li>Created "key" for use in dictionaries and parameters, rather
than relying on identifier (#702). Identifiers have a separate
minimum supported size.</li>
<li>Expanded the range of special characters allowed in identifier
to include all of ALPHA, ".", ":", and "%" (#702).</li>
<li>Use "?" instead of "!" to indicate a Boolean (#719).</li>
<li>Added "Intentionally Strict Processing" (#684).</li>
<li>Gave better names for referring specs to use in Parameterised
Lists (#720).</li>
<li>Added Lists of Lists (#721).</li>
<li>Rename Identifier to Token (#725).</li>
<li>Add implementation guidance (#727).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-07" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-07</name>
<ul spacing="normal">
<li>Make Dictionaries ordered mappings (#659).</li>
<li>Changed "binary content" to "byte sequence" to align with Infra
specification (#671).</li>
<li>Changed "mapping" to "map" for #671.</li>
<li>Don't fail if byte sequences aren't "=" padded (#658).</li>
<li>Add Booleans (#683).</li>
<li>Allow identifiers in items again (#629).</li>
<li>Disallowed whitespace before items (#703).</li>
<li>Explain the consequences of splitting a string across multiple
headers (#686).</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-06" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-06</name>
<ul spacing="normal">
<li>Add a FAQ.</li>
<li>Allow non-zero pad bits.</li>
<li>Explicitly check for integers that violate constraints.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-05" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-05</name>
<ul spacing="normal">
<li>Reorganise specification to separate parsing out.</li>
<li>Allow referencing specs to use ABNF.</li>
<li>Define serialisation algorithms.</li>
<li>Refine relationship between ABNF, parsing and serialisation
algorithms.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-04" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-04</name>
<ul spacing="normal">
<li>Remove identifiers from item.</li>
<li>Remove most limits on sizes.</li>
<li>Refine number parsing.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-03" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-03</name>
<ul spacing="normal">
<li>Strengthen language around failure handling.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-02" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-02</name>
<ul spacing="normal">
<li>Split Numbers into Integers and Floats.</li>
<li>Define number parsing.</li>
<li>Tighten up binary parsing and give it an explicit end
delimiter.</li>
<li>Clarify that mappings are unordered.</li>
<li>Allow zero-length strings.</li>
<li>Improve string parsing algorithm.</li>
<li>Improve limits in algorithms.</li>
<li>Require parsers to combine header fields before processing.</li>
<li>Throw an error on trailing garbage.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-01" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-01</name>
<ul spacing="normal">
<li>Replaced with draft-nottingham-structured-headers.</li>
</ul>
</section>
<section anchor="since-draft-ietf-httpbis-header-structure-00" numbered="t
rue" toc="default">
<name>Since draft-ietf-httpbis-header-structure-00</name>
<ul spacing="normal">
<li>Added signed 64bit integer type.</li>
<li>Drop UTF8, and settle on BCP137 ::EmbeddedUnicodeChar for
h1-unicode-string.</li>
<li>Change h1_blob delimiter to ":" since "'" is valid t_char</li>
</ul>
</section>
</section> </section>
<section numbered="false" anchor="acknowledgements" toc="default"> <section numbered="false" anchor="acknowledgements">
<name>Acknowledgements</name> <name>Acknowledgements</name>
<t>Many thanks to <contact fullname="Matthew Kerwin"/> for his detailed fe edback and careful <t>Many thanks to <contact fullname="Matthew Kerwin"/> for his detailed fe edback and careful
consideration during the development of this specification.</t> consideration during the development of this specification.</t>
<t>Thanks also to <contact fullname="Ian Clelland"/>, <contact <t>Thanks also to <contact fullname="Ian Clelland"/>, <contact fullname="R
fullname="Roy Fielding"/>, <contact fullname="Anne van Kesteren"/>, oy Fielding"/>, <contact fullname="Anne van Kesteren"/>,
<contact fullname="Kazuho Oku"/>, <contact fullname="Evert Pot"/>, <contact fullname="Kazuho Oku"/>, <contact fullname="Evert Pot"/>,
<contact fullname="Julian Reschke"/>, <contact fullname="Martin <contact fullname="Julian Reschke"/>, <contact fullname="Martin Thom
Thomson"/>, <contact fullname="Mike West"/>, and <contact son"/>, <contact fullname="Mike West"/>, and <contact fullname="Jeffrey Yasskin"
fullname="Jeffrey Yasskin"/> for their contributions.</t> /> for their contributions.</t>
</section> </section>
</back> </back>
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