GZIP file format specification version 4.3
RFC 1952
Document | Type |
RFC - Informational
(May 1996; No errata)
Was draft-deutsch-gzip-spec (individual)
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Author | L. Deutsch | ||
Last updated | 2013-03-02 | ||
Stream | Legacy | ||
Formats | plain text html pdf ps htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1952 (Informational) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group P. Deutsch Request for Comments: 1952 Aladdin Enterprises Category: Informational May 1996 GZIP file format specification version 4.3 Status of This Memo This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. IESG Note: The IESG takes no position on the validity of any Intellectual Property Rights statements contained in this document. Notices Copyright (c) 1996 L. Peter Deutsch Permission is granted to copy and distribute this document for any purpose and without charge, including translations into other languages and incorporation into compilations, provided that the copyright notice and this notice are preserved, and that any substantive changes or deletions from the original are clearly marked. A pointer to the latest version of this and related documentation in HTML format can be found at the URL <ftp://ftp.uu.net/graphics/png/documents/zlib/zdoc-index.html>. Abstract This specification defines a lossless compressed data format that is compatible with the widely used GZIP utility. The format includes a cyclic redundancy check value for detecting data corruption. The format presently uses the DEFLATE method of compression but can be easily extended to use other compression methods. The format can be implemented readily in a manner not covered by patents. Deutsch Informational [Page 1] RFC 1952 GZIP File Format Specification May 1996 Table of Contents 1. Introduction ................................................... 2 1.1. Purpose ................................................... 2 1.2. Intended audience ......................................... 3 1.3. Scope ..................................................... 3 1.4. Compliance ................................................ 3 1.5. Definitions of terms and conventions used ................. 3 1.6. Changes from previous versions ............................ 3 2. Detailed specification ......................................... 4 2.1. Overall conventions ....................................... 4 2.2. File format ............................................... 5 2.3. Member format ............................................. 5 2.3.1. Member header and trailer ........................... 6 2.3.1.1. Extra field ................................... 8 2.3.1.2. Compliance .................................... 9 3. References .................................................. 9 4. Security Considerations .................................... 10 5. Acknowledgements ........................................... 10 6. Author's Address ........................................... 10 7. Appendix: Jean-Loup Gailly's gzip utility .................. 11 8. Appendix: Sample CRC Code .................................. 11 1. Introduction 1.1. Purpose The purpose of this specification is to define a lossless compressed data format that: * Is independent of CPU type, operating system, file system, and character set, and hence can be used for interchange; * Can compress or decompress a data stream (as opposed to a randomly accessible file) to produce another data stream, using only an a priori bounded amount of intermediate storage, and hence can be used in data communications or similar structures such as Unix filters; * Compresses data with efficiency comparable to the best currently available general-purpose compression methods, and in particular considerably better than the "compress" program; * Can be implemented readily in a manner not covered by patents, and hence can be practiced freely; * Is compatible with the file format produced by the current widely used gzip utility, in that conforming decompressors will be able to read data produced by the existing gzip compressor. Deutsch Informational [Page 2] RFC 1952 GZIP File Format Specification May 1996 The data format defined by this specification does not attempt to: * Provide random access to compressed data; * Compress specialized data (e.g., raster graphics) as well as the best currently available specialized algorithms. 1.2. Intended audience This specification is intended for use by implementors of software to compress data into gzip format and/or decompress data from gzipShow full document text