Template:Zlib Header

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Zlib Header (source)
byte index bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
[0] CMF Compression info
  • 7 = indicates a 32K window size
 Compression method
  • 8 = denotes the "deflate" compression
[1] FLG FLEVEL
  • 0 - compressor used fastest algorithm
  • 1 - compressor used fast algorithm
  • 2 - compressor used default algorithm
  • 3 - compressor used maximum compression, slowest algorithm
 FDICT

(Preset dictionary) 

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.
FCHECK 
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.


About Data Compression:

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