A format developed as part of the snappy java library.

From the docs:

The output format is the stream header "snappy\0" followed by one or
more compressed blocks of data, each of which is preceded by a seven
byte header.

The first byte of the header is a flag indicating if the block is
compressed or not. A value of 0x00 means uncompressed, and 0x01 means
compressed.

The second and third bytes are the size of the block in the stream as
a big endian number. This value is never zero as empty blocks are
never written. The maximum allowed length is 32k (1 << 15).

The remaining four byes are crc32c checksum of the user input data
masked with the following function: {@code ((crc >>> 15) | (crc <<
17)) + 0xa282ead8 }

An uncompressed block is simply copied from the input, thus
guaranteeing that the output is never larger than the input (not
including the header).

Example encoding of the string "foobar\n":

00000000  73 6e 61 70 70 79 00 00  00 07 3a bb 17 0a 66 6f  |snappy....:...fo|
00000010  6f 62 61 72 0a                                    |obar.|

Reference: https://github.com/dain/snappy