FreeArc/Universal Archive Format

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It's description of FreeArc archive format and ideas how it can be further improved.

Archive block structure

Archive consists of blocks which divide into DATA BLOCKS (one datablock contains compressed data of one solid block) and CONTROL BLOCKS which stores archive meta-info (directories, comments, compression methods, recovery records...). Every block may be described by following info:

  • block type (0 - data block, 1.. - various control blocks)
  • its position in archive (number of first byte)
  • original size
  • compressed size
  • compression algorithm used to compress this block (usually all blocks are compressed, data blocks compression controlled by -m option, control blocks compression by -dm option)
  • CRC32 of original data - used to check block consistency