From 0d054955d48711279e152e123a5aa75cbb49b60c Mon Sep 17 00:00:00 2001
From: drfrugal <drfrugal@karazhan>
Date: Fri, 7 Mar 2025 21:15:18 +0100
Subject: init

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 create mode 100644 README.md

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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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