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The .xz file format version 1.0.1

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Lasse Collin 2009-06-01 14:53:57 +03:00
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doc/xz-file-format.txt
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@ -2,7 +2,7 @@
The .xz File Format The .xz File Format
=================== ===================
Version 1.0.0 (2009-01-14) Version 1.0.1 (2009-06-01)
0. Preface 0. Preface
@ -92,7 +92,12 @@ Version 1.0.0 (2009-01-14)
0.3. Version History 0.3. Version History
Version Date Description Version Date Description
1.0.0 2008-01-14 The first official version
1.0.1 2009-06-01 Typo fix in Section 0.3 and minor
clarifications to Sections 2, 2.2,
3.3, 4.4, and 5.3.2
1.0.0 2009-01-14 The first official version
1. Conventions 1. Conventions
@ -233,6 +238,10 @@ Version 1.0.0 (2009-01-14)
| Stream | Stream Padding | Stream | Stream Padding | ... | Stream | Stream Padding | Stream | Stream Padding | ...
+========+================+========+================+ +========+================+========+================+
The sizes of Stream and Stream Padding are always multiples
of four bytes, thus the size of every valid .xz file MUST be
a multiple of four bytes.
While a typical file contains only one Stream and no Stream While a typical file contains only one Stream and no Stream
Padding, a decoder handling standalone .xz files SHOULD support Padding, a decoder handling standalone .xz files SHOULD support
files that have more than one Stream or Stream Padding. files that have more than one Stream or Stream Padding.
@ -431,7 +440,8 @@ Version 1.0.0 (2009-01-14)
Stream Padding MUST contain only null bytes. To preserve the Stream Padding MUST contain only null bytes. To preserve the
four-byte alignment of consecutive Streams, the size of Stream four-byte alignment of consecutive Streams, the size of Stream
Padding MUST be a multiple of four bytes. Empty Stream Padding Padding MUST be a multiple of four bytes. Empty Stream Padding
is allowed. is allowed. If these requirements are not met, the decoder MUST
indicate an error.
Note that non-empty Stream Padding is allowed at the end of the Note that non-empty Stream Padding is allowed at the end of the
file; there doesn't need to be a new Stream after non-empty file; there doesn't need to be a new Stream after non-empty
@ -597,7 +607,9 @@ Version 1.0.0 (2009-01-14)
Block Padding MUST contain 0-3 null bytes to make the size of Block Padding MUST contain 0-3 null bytes to make the size of
the Block a multiple of four bytes. This can be needed when the Block a multiple of four bytes. This can be needed when
the size of Compressed Data is not a multiple of four. the size of Compressed Data is not a multiple of four. If any
of the bytes in Block Padding are not null bytes, the decoder
MUST indicate an error.
3.4. Check 3.4. Check
@ -709,7 +721,8 @@ Version 1.0.0 (2009-01-14)
4.4. Index Padding 4.4. Index Padding
This field MUST contain 0-3 null bytes to pad the Index to This field MUST contain 0-3 null bytes to pad the Index to
a multiple of four bytes. a multiple of four bytes. If any of the bytes are not null
bytes, the decoder MUST indicate an error.
4.5. CRC32 4.5. CRC32
@ -901,8 +914,10 @@ Version 1.0.0 (2009-01-14)
If the size of Filter Properties is four bytes, the Filter If the size of Filter Properties is four bytes, the Filter
Properties field contains the start offset used for address Properties field contains the start offset used for address
conversions. It is stored as an unsigned 32-bit little endian conversions. It is stored as an unsigned 32-bit little endian
integer. If the size of Filter Properties is zero, the start integer. The start offset MUST be a multiple of the alignment
offset is zero. of the filter as listed in the table above; if it isn't, the
decoder MUST indicate an error. If the size of Filter
Properties is zero, the start offset is zero.
Setting the start offset may be useful if an executable has Setting the start offset may be useful if an executable has
multiple sections, and there are many cross-section calls. multiple sections, and there are many cross-section calls.