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+# zlib-header-cli
+CLI to print details about the 2 Byte zlib header, as defined in
+[RFC 1950](https://datatracker.ietf.org/doc/html/rfc1950).  
+This was initially written to reverse-engineer more details about Blizzard's proprietary MPQ archive format, which uses
+zlib streams to store data.  
+```
+Usage: zlib-header-cli [OPTIONS] [HEX4CHAR]
+
+Arguments:
+[HEX4CHAR]  A four-character hex string representing the ZlibHeader (Big Endian)
+
+Options:
+  -e, --explain  Explain the ZlibHeader struct and abbreviations
+  -h, --help     Print help
+```
+```
+drfrugal@karazhan:~$ zlib-header-cli 789C
+CM      8 (DEFLATE)
+CINFO   7 (Window: 32768 Bytes)
+FCHECK  28 (valid)
+FDICT   false (Preset Dictionary not used)
+FLEVEL  2 (default)
+```
+```
+drfrugal@karazhan:~$ zlib-header-cli --explain
+2 Byte zlib header according to https://datatracker.ietf.org/doc/html/rfc1950
+1st Byte - CMF (Compression Method and Flags)
+  0000_1111  CM      Compression Method   8, _ (DEFLATE, UNDEFINED)
+  1111_0000  CINFO   Compression Info     window size is 2.pow(CINFO + 8)
+2nd Byte - FLG (Flags)
+  0001_1111  FCHECK  Checksum Adjustment  valid if (CMF * 256 + FLG) % 31 == 0
+  0010_0000  FDICT   Preset Dictionary    a preset dictionary was used
+  1100_0000  FLEVEL  Compression Level    0, 1, 2, 3 (fastest, fast, default, best)
+```