rfc8878v3.txt   rfc8878.txt 
Internet Engineering Task Force (IETF) Y. Collet Internet Engineering Task Force (IETF) Y. Collet
Request for Comments: 8878 M. Kucherawy, Ed. Request for Comments: 8878 M. Kucherawy, Ed.
Obsoletes: 8478 Facebook Obsoletes: 8478 Facebook
Category: Informational January 2021 Category: Informational February 2021
ISSN: 2070-1721 ISSN: 2070-1721
Zstandard Compression and the 'application/zstd' Media Type Zstandard Compression and the 'application/zstd' Media Type
Abstract Abstract
Zstandard, or "zstd" (pronounced "zee standard"), is a lossless data Zstandard, or "zstd" (pronounced "zee standard"), is a lossless data
compression mechanism. This document describes the mechanism and compression mechanism. This document describes the mechanism and
registers a media type, content encoding, and a structured syntax registers a media type, content encoding, and a structured syntax
suffix to be used when transporting zstd-compressed content via MIME. suffix to be used when transporting zstd-compressed content via MIME.
skipping to change at line 2015 skipping to change at line 2015
As discussed in Section 3.1.2, it is possible to store arbitrary user As discussed in Section 3.1.2, it is possible to store arbitrary user
metadata in skippable frames. While such frames are ignored during metadata in skippable frames. While such frames are ignored during
decompression of the data, they can be used as a watermark to track decompression of the data, they can be used as a watermark to track
the path of the compressed payload. the path of the compressed payload.
9. References 9. References
9.1. Normative References 9.1. Normative References
[ZSTD] "Zstandard", 2017, <http://www.zstd.net>. [ZSTD] "Zstandard", <http://www.zstd.net>.
9.2. Informative References 9.2. Informative References
[ANS] Duda, J., "Asymmetric numeral systems: entropy coding [ANS] Duda, J., "Asymmetric numeral systems: entropy coding
combining speed of Huffman coding with compression rate of combining speed of Huffman coding with compression rate of
arithmetic coding", January 2014, arithmetic coding", January 2014,
<https://arxiv.org/pdf/1311.2540>. <https://arxiv.org/pdf/1311.2540>.
[CRIME] "CRIME", June 2018, <https://en.wikipedia.org/w/ [CRIME] "CRIME", June 2018, <https://en.wikipedia.org/w/
index.php?title=CRIME&oldid=844538656>. index.php?title=CRIME&oldid=844538656>.
skipping to change at line 2050 skipping to change at line 2050
<https://github.com/Cyan4973/FiniteStateEntropy/>. <https://github.com/Cyan4973/FiniteStateEntropy/>.
[LZ4] "LZ4 Frame Format Description", commit ec735ac, January [LZ4] "LZ4 Frame Format Description", commit ec735ac, January
2019, <https://github.com/lz4/lz4/blob/master/doc/ 2019, <https://github.com/lz4/lz4/blob/master/doc/
lz4_Frame_format.md>. lz4_Frame_format.md>.
[RFC1952] Deutsch, P., "GZIP file format specification version 4.3", [RFC1952] Deutsch, P., "GZIP file format specification version 4.3",
RFC 1952, DOI 10.17487/RFC1952, May 1996, RFC 1952, DOI 10.17487/RFC1952, May 1996,
<https://www.rfc-editor.org/info/rfc1952>. <https://www.rfc-editor.org/info/rfc1952>.
[XXHASH] "xxHash", 2017, <http://www.xxhash.org>. [XXHASH] "xxHash", <http://www.xxhash.org>.
Appendix A. Decoding Tables for Predefined Codes Appendix A. Decoding Tables for Predefined Codes
This appendix contains FSE decoding tables for the predefined This appendix contains FSE decoding tables for the predefined
literals length, match length, and offset codes. The tables have literals length, match length, and offset codes. The tables have
been constructed using the algorithm as given above in Section 4.1.1. been constructed using the algorithm as given above in Section 4.1.1.
The tables here can be used as examples to crosscheck that an The tables here can be used as examples to crosscheck that an
implementation has built its decoding tables correctly. implementation has built its decoding tables correctly.
A.1. Literals Length Code Table A.1. Literals Length Code Table
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