< draft-deutsch-zlib-spec-02.txt   draft-deutsch-zlib-spec-03.txt >
INTERNET-DRAFT L. Peter Deutsch INTERNET-DRAFT L. Peter Deutsch
ZLIB 3.3 Aladdin Enterprises ZLIB 3.3 Aladdin Enterprises
Expires: 16 Sep 1996 Jean-Loup Gailly Expires: 26 Sep 1996 Jean-Loup Gailly
Info-Zip Info-ZIP
11 Mar 1996 21 Mar 1996
ZLIB Compressed Data Format Specification version 3.3 ZLIB Compressed Data Format Specification version 3.3
File draft-deutsch-zlib-spec-02.txt File draft-deutsch-zlib-spec-03.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as ``work in progress.'' material or to cite them other than as ``work in progress.''
To learn the current status of any Internet-Draft, please check the To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet- Drafts ``1id-abstracts.txt'' listing contained in the Internet- Drafts
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Distribution of this memo is unlimited. Distribution of this memo is unlimited.
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Notices Notices
Copyright (c) 1996 L. Peter Deutsch and Jean-loup Gailly Copyright (c) 1996 L. Peter Deutsch and Jean-loup Gailly
Permission is granted to copy and distribute this document for any Permission is granted to copy and distribute this document for any
purpose and without charge, including translations into other purpose and without charge, including translations into other
languages and incorporation into compilations, provided that it is languages and incorporation into compilations, provided that the
copied as a whole (including the copyright notice and this notice) copyright notice and this notice are preserved, and that any
and with no changes. substantive changes or deletions from the original are clearly
marked.
Deutsch and Gailly [Page 1] Deutsch and Gailly [Page 1]
Abstract Abstract
This specification defines a lossless compressed data format. The This specification defines a lossless compressed data format. The
data can be produced or consumed, even for an arbitrarily long data can be produced or consumed, even for an arbitrarily long
sequentially presented input data stream, using only an a priori sequentially presented input data stream, using only an a priori
bounded amount of intermediate storage. The format presently uses bounded amount of intermediate storage. The format presently uses
the DEFLATE compression method but can be easily extended to use the DEFLATE compression method but can be easily extended to use
other compression methods. It can be implemented readily in a manner other compression methods. It can be implemented readily in a manner
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able to accept and decompress any data set that conforms to all able to accept and decompress any data set that conforms to all
the specifications presented here; a compliant compressor must the specifications presented here; a compliant compressor must
produce data sets that conform to all the specifications presented produce data sets that conform to all the specifications presented
here. here.
1.5. Definitions of terms and conventions used 1.5. Definitions of terms and conventions used
byte: 8 bits stored or transmitted as a unit (same as an octet). byte: 8 bits stored or transmitted as a unit (same as an octet).
(For this specification, a byte is exactly 8 bits, even on (For this specification, a byte is exactly 8 bits, even on
machines which store a character on a number of bits different machines which store a character on a number of bits different
from 8.) See below, for the numbering of bits within a byte. from 8.) See below, for the numbering of bits within a byte.
1.6. Changes from previous versions 1.6. Changes from previous versions
Version 3.1 was the first public release of this specification. Version 3.1 was the first public release of this specification.
In version 3.2, some terminology was changed and the Adler-32 In version 3.2, some terminology was changed and the Adler-32
sample code was rewritten for clarity. In version 3.3, the sample code was rewritten for clarity. In version 3.3, the
support for a preset dictionary was introduced, and the support for a preset dictionary was introduced, and the
specification was converted to Internet Draft style. specification was converted to Internet Draft style.
Deutsch and Gailly [Page 3] Deutsch and Gailly [Page 3]
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identifier of a known preset dictionary. A decompressor may identifier of a known preset dictionary. A decompressor may
ignore FLEVEL and still be compliant. When the zlib data format ignore FLEVEL and still be compliant. When the zlib data format
is being used as a part of another standard format, a compliant is being used as a part of another standard format, a compliant
decompressor must support all the preset dictionaries specified by decompressor must support all the preset dictionaries specified by
the other format. When the other format does not use the preset the other format. When the other format does not use the preset
dictionary feature, a compliant decompressor must reject any dictionary feature, a compliant decompressor must reject any
stream in which the FDICT flag is set. stream in which the FDICT flag is set.
3. References 3. References
[1] Deutsch, L.P.,"'Gzip' Compressed Data Format Specification". [1] Deutsch, L.P.,"'Gzip' Compressed Data Format Specification",
available in ftp.uu.net:/pub/archiving/zip/doc/gzip-*.doc available in ftp.uu.net:/pub/archiving/zip/doc/gzip-*.doc
[2] Thomas Boutell, "PNG (Portable Network Graphics) specification". [2] Thomas Boutell, "PNG (Portable Network Graphics) specification",
available in ftp://ftp.uu.net/graphics/png/png* available in ftp://ftp.uu.net/graphics/png/png*
[3] Deutsch, L.P.,"'Deflate' Compressed Data Format Specification". [3] Deutsch, L.P.,"'Deflate' Compressed Data Format Specification",
available in ftp.uu.net:/pub/archiving/zip/doc/deflate-*.doc available in ftp.uu.net:/pub/archiving/zip/doc/deflate-*.doc
[4] Fletcher, J. G., "An Arithmetic Checksum for Serial [4] Fletcher, J. G., "An Arithmetic Checksum for Serial
Transmissions," IEEE Transactions on Communications, Vol. COM-30, Transmissions," IEEE Transactions on Communications, Vol. COM-30,
No. 1, January 1982, pp. 247-252. No. 1, January 1982, pp. 247-252.
[5] ITU-T Recommendation X.224, Annex D, "Checksum Algorithms," [5] ITU-T Recommendation X.224, Annex D, "Checksum Algorithms,"
November, 1993, pp. 144, 145. (Available from November, 1993, pp. 144, 145. (Available from
gopher://info.itu.ch). ITU-T X.244 is also the same as ISO 8073. gopher://info.itu.ch). ITU-T X.244 is also the same as ISO 8073.
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