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# zlib-header
Rust binary and library to work with 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.
## Binary
```
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)
```
## Library
Read the complete documentation [here](https://git.drfrugal.xyz/doc/zlib_header/).
```
use zlib_header::ZlibHeader;
let cm = 8;
let cinfo = 7;
let fdict = false;
let flevel = 2;
let header = ZlibHeader::new(cm, cinfo, fdict, flevel);
match header {
Ok(header) => {
println!("header is valid (strict): {}", header.is_valid_strict()); // header is valid (strict): true
},
Err(err) => eprintln!("Unable to initialize zlib header: {:?}", err)
}
```
```
use zlib_header::ZlibHeader;
let header = ZlibHeader::default();
println!("Display: {}", header); // Display: 789C
println!("Debug: {:?}", header); // Debug: ZlibHeader { DEFLATE | 32768 Bytes | default | Dictionary: false | valid }
let bytes = [0x78, 0x9C];
println!("header matches expected bytes: {}", header == bytes); // header matches expected bytes: true
```
## Downloads
[linux/x86_64/zlib-header-cli](https://git.drfrugal.xyz/bin/linux/x86_64/zlib-header-cli)
[windows/x86_64/zlib-header-cli.exe](https://git.drfrugal.xyz/bin/windows/x86_64/zlib-header-cli.exe)
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