This small extension wraps zlib to add several functions for data compression/decompression to GameMaker: Studio (1, 2).

Since the extension is freeware and I'm not particularly familiar with zlib, this repository is intended as a "do it yourself" kind of thing for anyone desiring additional features/platforms. Feel free to send back a pull request if you do something nice.

• Clone/download the repository.
• Download zlib. I've been using v1.2.11 as of writing this.

• Copy all .h / .c files (zlib.h, inflate.c, etc) from zlib directory into buffer_zlib directory of the repository.
• Open buffer_zlib.sln in Visual Studio. I've been using Community Edition 2015 as of writing this.
• If all was done correctly, the project should now produce a valid DLL when in x86 release mode.
• If you want the extension function list to be automatically updated post-compile, download gmxgen and tuck it's executable files at some PATH environment variable location.

• Copy all .h / .c files (zlib.h, inflate.c, etc) from zlib directory into buffer_zlib.java\jni directory of the repository.
• Run _javaclass BAT to compile java class from BufferZlib.java. BufferZlib.class shall appear in the buffer_zlib.java\bin\com\gamemaker\bufferzlib directory.
• Run _jniheader BAT. It should produce com_gamemaker_bufferzlib_BufferZlib.h header based on the java class. You need to place this file into buffer_zlib.java\jni.
• Header is the link between .java and .cpp sources. Methods in buffer_zlib.cpp should match the methods from com_gamemaker_bufferzlib_BufferZlib.h which are generated based on the methods from BufferZlib.java.
• Run _libs.bat to build NDK Shared Library. If all was done correctly, you will see two newly created directories, obj and libs. Copy libs folder and name it lib.
• Go to lib directory and delete all architectures not supported by GameMaker. Currently supported architecures are: armeabi, armeabi-v7a, mips and x86, which should stay. If you build your games without supporting some of architecures (see Android Settings of your project) you can delete it too.
• Add lib directory to a zip file. Path of directory should be saved, so it shall be lib.zip\lib\*.
• Rename lib.zip into lib.jar and copy it into AndroidSource\libs directory of GameMaker extension.
• Copy BufferZlib.java and BufferZlibExt.java into AndroidSource\Java directory of GameMaker extension. BufferZlibExt.java is the main file, so Class Name in Android extension settings should be BufferZlibExt.
• Tested SDKs: jdk/jre 1.8.0, Target SDK 25, Min SDK 9, Compile SDK 25, Build Tools 26, Support Lib 25.3.1, NDK r14b.

See zlib license.