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Bzip3 #673

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152d21f
add specification for bzip3
armijnhemel May 15, 2023
41fef77
bizp3: add reference, add doc string, add validation check
armijnhemel May 12, 2025
4d73147
bzip3: change license, remove encoding, various cosmetic fixes, block…
armijnhemel May 12, 2025
3338f25
bzip3: fix length check, explain is_last instance
armijnhemel May 12, 2025
03ad5f5
bzip3: fix doc
armijnhemel May 12, 2025
f33c2af
bzip3: fix length check
armijnhemel May 12, 2025
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45 changes: 45 additions & 0 deletions archive/bzip3.ksy
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
meta:
id: bzip3
title: Bzip3 header
file-extension: bz3
license: LGPL-3.0
encoding: UTF-8
endian: le
doc:
bzip3 is a decompression tool and library. Depending on whether or not the
CLI or the library is used the file format is slightly different. This
specification describes the structure of the format as generated by the CLI
(header and chunks, not blocks).
doc-ref:
- https://github.com/kspalaiologos/bzip3
- https://github.com/kspalaiologos/bzip3/blob/972e6694b815/doc/bzip3_format.md
seq:
- id: header
type: header
- id: blocks
type: compressed_data_block
repeat: until
repeat-until: _io.eof or _.is_last
types:
header:
seq:
- id: signature
contents: 'BZ3v1'
- id: block_size
type: u4
valid:
min: 66560
max: 535822336
compressed_data_block:
seq:
- id: len_compressed
type: u4
- id: len_uncompressed
type: u4
valid:
max: _root.header.block_size
- id: data
size: len_compressed
instances:
is_last:
value: len_uncompressed < _root.header.block_size
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@generalmimon generalmimon May 12, 2025

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Are you sure about this? Can you back it up with a link to https://github.com/kspalaiologos/bzip3 as a source, perhaps?

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@armijnhemel armijnhemel May 12, 2025

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The bzip3 doesn't take concatenated files into account but will just try to continue. For my particular use case (where I need to be able to carve) it is actually important. So no, it isn't in the specification.

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@generalmimon generalmimon May 12, 2025 •
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Could you please explain this in a doc somewhere why this .ksy spec does this while the reference implementation does not? Because it's confusing at least.

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@armijnhemel armijnhemel May 12, 2025

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Yes, it is a bit confusing, and it also doesn't work in all cases (so I need to work a bit more on expanding the specification). Would you prefer if I would first add additional block parsing?