puffin

Module file_format

Source
Expand description

§Format specification for Puffin files

§File structure

Magic Blob₁ Blob₂ … Blobₙ Footer

  • Magic is four bytes 0x50, 0x46, 0x41, 0x31 (short for: Puffin Fratercula arctica, version 1),
  • Blobᵢ is i-th blob contained in the file, to be interpreted by application according to the footer,
  • Footer is defined below.

Magic FooterPayload FooterPayloadSize Flags Magic

  • Magic: four bytes, same as at the beginning of the file
  • FooterPayload: optionally compressed, UTF-8 encoded JSON payload describing the blobs in the file, with the structure described below
  • FooterPayloadSize: a length in bytes of the FooterPayload (after compression, if compressed), stored as 4 byte integer
  • Flags: 4 bytes for boolean flags
    • byte 0 (first)
      • bit 0 (lowest bit): whether FooterPayload is compressed
      • all other bits are reserved for future use and should be set to 0 on write
    • all other bytes are reserved for future use and should be set to 0 on write A 4 byte integer is always signed, in a two’s complement representation, stored little-endian.

Footer payload bytes is either uncompressed or LZ4-compressed (as a single LZ4 compression frame with content size present), UTF-8 encoded JSON payload representing a single FileMetadata object.

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