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Added Z2 System Use Entry Format to zisofs2 specs

Thomas Schmitt 4 months ago
1 changed files with 24 additions and 1 deletions
  1. +24

+ 24
- 1
doc/zisofs2_format.txt View File

@ -12,7 +12,7 @@ The zisofs2 format was invented by Valentín KIVACHUK BURDÁ and
Thomas SCHMITT (as extension of zisofs by H. Peter Anvin). It compresses
data file content, marks it by a header and provides a pointer array for
coarse random access. Within a RRIP enhanced ISO 9660 image the format
is additionally marked by a System Use entry with signature "ZF".
is additionally marked by a System Use entry with signature "ZF" or "Z2".
The uncompressed size of a single zisofs2 compressed file is restricted
to 2^64 - 1 bytes. Larger files shall not be compressed.
@ -146,6 +146,25 @@ Example (block size 128 kiB, uncompressed file size = 40 TB):
0x00, 0x80, 0xCA, 0x39, 0x61, 0x24, 0x00, 0x00 }
Z2 System Use Entry Format
Linux kernels which are configured by CONFIG_ZISOFS to recognize zisofs
but are not aware of zisofs2 will complain about ZF entries which announce
algorithms other than "pz". The system log will show for each zisofs2
compressed file at first stat(2) or open(2) a line like this:
isofs: Unknown ZF compression algorithm: PZ
To avoid these complaints, it is possible to use
[1] "BP 1 to BP 2 - Signature Word" shall be (5A)(32) ("Z2").
instead of "ZF" with the System Use Entry Format specified above.
Everything else shall be like in ZF format version 2, including the version
number itself:
[3] "BP 4 - System Use Entry Version" shall be 2 as in ISO 9660:7.1.1.
@ -225,6 +244,10 @@ SUSP 1.12
RRIP 1.12
zisofs version 1
This text is under