NAME

     snappy, unsnappy — Snappy compression and decompression with and without framing

SYNOPSIS

     snappy [-f] [file] > snappy.sn|.sz

     snappy -d [-i] [file]
     unsnappy [-i] [file]

DESCRIPTION

     Without -d, compresses file (standard input stream if "-", the default) with Snappy to the
     standard output stream, then assesses the compression ratio achieved to the standard error
     stream.
     With -f, the Snappy framing format is produced.

     When run as unsnappy, or with -d, decompresses file (likewise) from Snappy, or the Snappy
     framing format (detected automatically), to the standard output stream.
     With -i, decompression and framing errors are ignored and processing continues.

     As a format limitation, if file isn't seekable when producing or decompressing unframed
     Snappy streams, it will be read into memory in its entirety.

EXIT STATUS

     1  If a decompression error (invalid or truncated Snappy block) or a framing error (Stream
        identifier (0xFF) frame invalid, unknown reserved unskippable chunk ([0x02, 0x7F]) frame
        encountered, checksum mismatch).
     2  On an I/O error.
     3  When compressing without -f and file is larger than 4GiB.  (Output unaffected, but see
        BUGS.)

DIAGNOSTICS

     After compressing,
           data: 2048576 -> 1099105 (53.65%)
     means that the file data was 2048576 bytes, which were compressed down to 1099105 bytes, and
     the output is thus 53.65% the size.

SEE ALSO

     The Snappy homepage: https://google.github.io/snappy/

CONFORMING TO

     The framed format, with MIME type ‘application/x-snappy-framed’, version 2013-10-25: Snappy
     framing format description: https://github.com/google/snappy/blob/main/framing_format.txt.

     The unframed format, as described in Snappy compressed format description:
     https://github.com/google/snappy/blob/main/format_description.txt, as provided by the
     upstream Fast Compressor/Decompressor Library (libsnappy, -lsnappy).

BUGS

     The largest representable unframed stream is of size 4GiB-1B (= 4·1024·1024·1024B-1B
     = 4294967295B).  Above this size the length stored in the header becomes mangled, so the
     stream may be semantically correct but will produce an incorrect (short) output when
     decompressing.  snappy warns about this and exits 3.

     On 32-bit systems it is impossible to produce unframed streams from files larger than
     4GiB-1B at all due to an API limitation (EXIT STATUS 2).  On 32-bit systems the output size
     and compression ratio will be misrepresented if compression produces an unframed output
     larger than 4GiB-1B.  It is also impossible to decompress such files there.

     Supposedly, compressors which produce checksums with inverted byte order exist in the wild.