mirror of https://git.tukaani.org/xz.git
The .xz file format specification version 1.0.0 is now
officially released. The format has been technically the same since 2008-11-19, but now that it is frozen, people can start using it without a fear that the format will break.
This commit is contained in:
parent
c4683a660b
commit
982da7ed31
|
@ -1,10 +1,14 @@
|
|||
|
||||
The .xz File Format
|
||||
-------------------
|
||||
===================
|
||||
|
||||
Version 1.0.0 (2009-01-14)
|
||||
|
||||
|
||||
0. Preface
|
||||
0.1. Notices and Acknowledgements
|
||||
0.2. Changes
|
||||
0.2. Getting the Latest Version
|
||||
0.3. Version History
|
||||
1. Conventions
|
||||
1.1. Byte and Its Representation
|
||||
1.2. Multibyte Integers
|
||||
|
@ -61,29 +65,34 @@ The .xz File Format
|
|||
this format replace the old .lzma format used by LZMA SDK and
|
||||
LZMA Utils.
|
||||
|
||||
IMPORTANT: The version described in this document is a
|
||||
draft, NOT a final, official version. Changes
|
||||
are possible.
|
||||
|
||||
|
||||
0.1. Notices and Acknowledgements
|
||||
|
||||
This file format was designed by Lasse Collin
|
||||
<lasse.collin@tukaani.org> and Igor Pavlov.
|
||||
|
||||
Special thanks for helping with this document goes to Ville
|
||||
Koskinen. Thanks for helping with this document goes to
|
||||
Special thanks for helping with this document goes to
|
||||
Ville Koskinen. Thanks for helping with this document goes to
|
||||
Mark Adler, H. Peter Anvin, Mikko Pouru, and Lars Wirzenius.
|
||||
|
||||
This document has been put into the public domain.
|
||||
|
||||
|
||||
0.2. Changes
|
||||
0.2. Getting the Latest Version
|
||||
|
||||
Last modified: 2008-12-05 12:45+0200
|
||||
The latest official version of this document can be downloaded
|
||||
from <http://tukaani.org/xz/xz-file-format.txt>.
|
||||
|
||||
(A changelog will be kept once the first official version
|
||||
is made.)
|
||||
Specific versions of this document have a filename
|
||||
xz-file-format-X.Y.Z.txt where X.Y.Z is the version number.
|
||||
For example, the version 1.0.0 of this document is available
|
||||
at <http://tukaani.org/xz/xz-file-format-1.0.0.txt>.
|
||||
|
||||
|
||||
0.3. Version History
|
||||
|
||||
Version Date Description
|
||||
1.0.0 2008-01-14 The first official version
|
||||
|
||||
|
||||
1. Conventions
|
||||
|
@ -171,7 +180,7 @@ The .xz File Format
|
|||
variable-length integers. The functions return the number of
|
||||
bytes occupied by the integer (1-9), or zero on error.
|
||||
|
||||
#include <sys/types.h>
|
||||
#include <stddef.h>
|
||||
#include <inttypes.h>
|
||||
|
||||
size_t
|
||||
|
@ -429,9 +438,9 @@ The .xz File Format
|
|||
Stream Padding. This can be convenient in certain situations
|
||||
[GNU-tar].
|
||||
|
||||
The possibility of Padding MUST be taken into account when
|
||||
designing an application that parses Streams backwards, and
|
||||
the application supports concatenated Streams.
|
||||
The possibility of Stream Padding MUST be taken into account
|
||||
when designing an application that parses Streams backwards,
|
||||
and the application supports concatenated Streams.
|
||||
|
||||
|
||||
3. Block
|
||||
|
@ -599,19 +608,19 @@ The .xz File Format
|
|||
The Check, when used, is calculated from the original
|
||||
uncompressed data. If the calculated Check does not match the
|
||||
stored one, the decoder MUST indicate an error. If the selected
|
||||
type of Check is not supported by the decoder, it MUST indicate
|
||||
a warning or error.
|
||||
type of Check is not supported by the decoder, it SHOULD
|
||||
indicate a warning or error.
|
||||
|
||||
|
||||
4. Index
|
||||
|
||||
+-----------------+=========================+
|
||||
| Index Indicator | Number of Index Records |
|
||||
+-----------------+=========================+
|
||||
+-----------------+===================+
|
||||
| Index Indicator | Number of Records |
|
||||
+-----------------+===================+
|
||||
|
||||
+=================+=========+-+-+-+-+
|
||||
---> | List of Records | Padding | CRC32 |
|
||||
+=================+=========+-+-+-+-+
|
||||
+=================+===============+-+-+-+-+
|
||||
---> | List of Records | Index Padding | CRC32 |
|
||||
+=================+===============+-+-+-+-+
|
||||
|
||||
Index serves several purporses. Using it, one can
|
||||
- verify that all Blocks in a Stream have been processed;
|
||||
|
@ -656,11 +665,11 @@ The .xz File Format
|
|||
Unpadded Size and Uncompressed Size of the respective Blocks.
|
||||
|
||||
Implementation hint: It is possible to verify the Index with
|
||||
constant memory usage by calculating for example SHA256 of both
|
||||
the real size values and the List of Records, then comparing
|
||||
the check values. Implementing this using non-cryptographic
|
||||
check like CRC32 SHOULD be avoided unless small code size is
|
||||
important.
|
||||
constant memory usage by calculating for example SHA-256 of
|
||||
both the real size values and the List of Records, then
|
||||
comparing the hash values. Implementing this using
|
||||
non-cryptographic hash like CRC32 SHOULD be avoided unless
|
||||
small code size is important.
|
||||
|
||||
If the decoder supports random-access reading, it MUST verify
|
||||
that Unpadded Size and Uncompressed Size of every completely
|
||||
|
@ -898,7 +907,7 @@ The .xz File Format
|
|||
Setting the start offset may be useful if an executable has
|
||||
multiple sections, and there are many cross-section calls.
|
||||
Taking advantage of this feature usually requires usage of
|
||||
the Subblock filter.
|
||||
the Subblock filter, whose design is not complete yet.
|
||||
|
||||
|
||||
5.3.3. Delta
|
||||
|
@ -985,6 +994,7 @@ The .xz File Format
|
|||
5.4.1. Reserved Custom Filter ID Ranges
|
||||
|
||||
Range Description
|
||||
0x0000_0300 - 0x0000_04FF Reserved to ease .7z compatibility
|
||||
0x0002_0000 - 0x0007_FFFF Reserved to ease .7z compatibility
|
||||
0x0200_0000 - 0x07FF_FFFF Reserved to ease .7z compatibility
|
||||
|
||||
|
@ -1001,7 +1011,7 @@ The .xz File Format
|
|||
the CRC32 and CRC64 values, and prints the calculated values
|
||||
as big endian hexadecimal strings to standard output.
|
||||
|
||||
#include <sys/types.h>
|
||||
#include <stddef.h>
|
||||
#include <inttypes.h>
|
||||
#include <stdio.h>
|
||||
|
||||
|
@ -1067,7 +1077,8 @@ The .xz File Format
|
|||
uint8_t buf[8192];
|
||||
|
||||
while (1) {
|
||||
const size_t buf_size = fread(buf, 1, 8192, stdin);
|
||||
const size_t buf_size
|
||||
= fread(buf, 1, sizeof(buf), stdin);
|
||||
if (buf_size == 0)
|
||||
break;
|
||||
|
||||
|
@ -1092,6 +1103,9 @@ The .xz File Format
|
|||
LZMA Utils - LZMA adapted to POSIX-like systems
|
||||
http://tukaani.org/lzma/
|
||||
|
||||
XZ Utils - The next generation of LZMA Utils
|
||||
http://tukaani.org/xz/
|
||||
|
||||
[RFC-1952]
|
||||
GZIP file format specification version 4.3
|
||||
http://www.ietf.org/rfc/rfc1952.txt
|
||||
|
@ -1102,12 +1116,12 @@ The .xz File Format
|
|||
http://www.ietf.org/rfc/rfc2119.txt
|
||||
|
||||
[GNU-tar]
|
||||
GNU tar 1.20 manual
|
||||
GNU tar 1.21 manual
|
||||
http://www.gnu.org/software/tar/manual/html_node/Blocking-Factor.html
|
||||
- Node 9.4.2 "Blocking Factor", paragraph that begins
|
||||
"gzip will complain about trailing garbage"
|
||||
- Note that this URL points to the latest version of the
|
||||
manual, and may some day not contain the note which is in
|
||||
1.20. For the exact version of the manual, download GNU
|
||||
tar 1.20: ftp://ftp.gnu.org/pub/gnu/tar/tar-1.20.tar.gz
|
||||
1.21. For the exact version of the manual, download GNU
|
||||
tar 1.21: ftp://ftp.gnu.org/pub/gnu/tar/tar-1.21.tar.gz
|
||||
|
||||
|
|
Loading…
Reference in New Issue