Why bother using this? Because LZHAM extracts and tests much faster, around 2x-3x faster than LZMA, with similar compression ratios.
Importantly, if you create any archives using this custom codec DLL, you'll (obviously) need this DLL to also extract these archives. The LZHAM v1.x bitstream format is locked in stone, so future DLL's using newer versions of LZHAM will be forwards and backwards compatible with this release.
You can find the source to the plugin on github here. The plugin itself lives in the lzham7zip directory.
InstallationI've uploaded precompiled DLL's for the x86 and x64 versions of 7-zip v15.12 here.
To use this, create a new directory named "codecs" wherever you installed 7-zip, then copy the correct DLL (either x86 or x64) into this directory. For example, if you've installed the 32-bit version of 7-zip, extract the file LzhamCodec_x86.dll into "C:\Program Files (x86)\7-Zip\codecs". For the 64-bit version, extract it into "C:\Program Files\7-Zip\codecs".
To verify the installation, enter "7z.exe i" in a command prompt (cmd.exe) to list all the installed codecs. You should see this:
0 ED 6F00181 AES256CBC
1 ED 4F71001 LZHAM
Build InstructionsIf you want to compile this yourself, first grab the source code to 7-zip v15.12 and extract the archive somewhere. Next, "git clone https://github.com/richgel999/lzham_codec_devel" into this directory. Your final directory structure should be:
11/21/2015 05:00 PM <DIR> .
11/21/2015 05:00 PM <DIR> ..
11/21/2015 05:00 PM <DIR> Asm
11/21/2015 05:00 PM <DIR> bin
11/21/2015 05:00 PM <DIR> C
11/21/2015 05:00 PM <DIR> CPP
11/21/2015 05:00 PM <DIR> DOC
11/21/2015 05:00 PM <DIR> lzham_codec_devel
Now load this Visual Studio solution: lzham_codec_devel/lzham7zip/LzhamCodec.sln.
It builds with VS 2010 and VS 2015. The DLL's will be output into the bin directory.