|byte index||bit 7||bit 6||bit 5||bit 4||bit 3||bit 2||bit 1||bit 0|
| CMF||Compression info
If set, a DICT dictionary identifier is present immediately after the FLG byte. The dictionary is a sequence of bytes which are initially fed to the compressor without producing any compressed output. DICT is the Adler-32 checksum of this sequence of bytes (see the definition of ADLER32 below). The decompressor can use this identifier to determine which dictionary has been used by the compressor.
value must be such that CMF and FLG, when viewed as a 16-bit unsigned integer stored in MSB order (CMF *256 + FLG), is a multiple of 31.