Bzip3

archive/bzip3.ksy

@@ -0,0 +1,62 @@
+meta:
+  id: bzip3
+  title: Bzip3 header
+  file-extension: bz3
+  license: CC0-1.0
+  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).
+
+  bzip3 assumes that the entire file is a bzip3 archive and will fail as there
+  is no reliable way to detect if data following a chunk is a next chunk or if
+  it is other data (like what happens in concatenated files).
+
+  A simple example to illustrate:
+
+  $ cp /bin/ls .
+  $ bzip3 ls
+  $ cat ls.bz3 ls > test.bz3
+  $ bz3cat test.bz3 > /dev/null
+  Failed to decode a block: Inconsistent headers.
+
+  If a potential chunk has an invalid length (len_compressed), then the end of
+  the file has been reached. This check will not always work as it is possible
+  to have data where the first four bytes will be a valid length. With
+  additional block parsing and CRC checks it will be possible to detect invalid
+  blocks. This is future work.
+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: max_block_size
+        type: u4
+        valid:
+          min: 66_560 # 65 KiB
+          max: 535_822_336 # 511 MiB
+  compressed_data_block:
+    seq:
+      - id: len_compressed
+        type: u4
+      - id: len_uncompressed
+        type: u4
+        valid:
+          max: _root.header.max_block_size
+      - id: data
+        size: len_compressed
+    instances:
+      is_last:
+        value: len_uncompressed <= _root.header.max_block_size