|
|
| Line 1: |
Line 1: |
| − | {{FormatInfo
| + | #REDIRECT [[bzip2]] |
| − | |name=bzip2
| + | |
| − | |formattype=electronic
| + | |
| − | |subcat=Compression
| + | |
| − | |extensions={{ext|bz2}}
| + | |
| − | |mimetypes={{mimetype|application/x-bzip2}}
| + | |
| − | |pronom={{PRONOM|x-fmt/268}}
| + | |
| − | |wikidata={{wikidata|Q27866052}}
| + | |
| − | |released=1997
| + | |
| − | }}
| + | |
| − | '''bzip2''' is a data compression algorithm and compressed file format. It was developed by Julian Seward.
| + | |
| − | | + | |
| − | == Identification ==
| + | |
| − | A bzip2 file starts with the byte pattern {{magic|42 5a 68 ?? 31 41 59 26 53 59}}.
| + | |
| − | | + | |
| − | The first three bytes are ASCII "{{magic|BZh}}". (For signature "{{magic|BZ0}}", refer to the original [[bzip]] format.) The "<code>h</code>" has been said to stand for "Huffman coding", but confirmation is needed.
| + | |
| − | | + | |
| − | The byte at offset 3 is a code for the block size. Its possible values range from <code>0x31</code> to <code>0x39</code> (ASCII "<code>1</code>" to "<code>9</code>").
| + | |
| − | | + | |
| − | The bytes at offset 4-9 are derived from the digits of the mathematical constant π ([[Binary-coded decimal|BCD]]-encoded).
| + | |
| − | | + | |
| − | The end-of-file marker uses magic number (hex) {{magic|17 72 45 38 50 90}}, derived from the square root of π. However, it is not byte-aligned. The result is that one of the following byte sequences appears beginning 10 bytes from the end of the file:
| + | |
| − | | + | |
| − | b9 22 9c 28 48
| + | |
| − | dc 91 4e 14 24
| + | |
| − | ee 48 a7 0a 12
| + | |
| − | 77 24 53 85 09
| + | |
| − | bb 92 29 c2 84
| + | |
| − | 5d c9 14 e1 42
| + | |
| − | 2e e4 8a 70 a1
| + | |
| − | 17 72 45 38 50
| + | |
| − | | + | |
| − | == Specifications ==
| + | |
| − | * [https://github.com/dsnet/compress/blob/master/doc/bzip2-format.pdf Unofficial specification by Joe Tsai]
| + | |
| − | | + | |
| − | == Software ==
| + | |
| − | * [https://sourceware.org/bzip2/ bzip2 and libbzip2]
| + | |
| − | * [[7-Zip]]
| + | |
| − | | + | |
| − | == Sample files ==
| + | |
| − | * {{DexvertSamples|archive/bz2}}
| + | |
| − | | + | |
| − | == See also ==
| + | |
| − | * [[Burrows–Wheeler transform]]
| + | |
| − | * [[bzip]] (predecessor)
| + | |
| − | | + | |
| − | == Links ==
| + | |
| − | * [[Wikipedia:Bzip2|Wikipedia article]]
| + | |
| − | * [https://sourceware.org/bzip2/ bzip2 and libbzip2 website]
| + | |
| − | * [https://github.com/corkami/pics/blob/master/binary/BZ2.png Chart of format details]
| + | |
| − | * [https://lwn.net/Articles/762264/ bzip.org changes hands] (LWN article from August 9, 2018)
| + | |
| − | * [{{ForensicsWikiURL|bzip2}} ForensicsWiki entry] (also includes more details on the headers)
| + | |
| − | * [http://www.bzip.org/ bzip.org]
| + | |
