BZIP2: Data Structure

BZIP2 data are always introduced by a header starting with the letters "BZ". Afterwards the identification of the block size immediately follows, being valid for the entire file ("h1 ", "h2", "h3" to "h9"). The parameter indicates the block size in units of 100,000 symbols each.

An internal file system is not specified, BZIP2 can only use the attributes of the local file system. Anyway only an individual file or a sequential concatenation of files may be encoded. From the file format neither file names nor time attributes can be reconstructed.

The actual original data are stored in blocks according to the selected size and will be protected individually with a CRC32 checksum. The error detection does not excede block boundaries and restarts with each new block.

Additionally a 48 bit identifier introduces each block. This block structure allows a partial reconstruction of damaged files, as described in the following.

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