Garry's Mod Addon

Garry's Mod Addon files are used in the PC game Garry's Mod for storing downloadable game content. They store game files in a hierarchy of folders, so gma files can be create from a folder, or extracted into a hierarchy of folders.

Format

 * char[4] ident
 * uint8 version
 * uint64 steam_id (unused)
 * uint64 timestamp
 * uint8 zero (0)
 * char addon_name (null terminated string of variable size)
 * char addon_description (null terminated string of variable size)
 * char addon_author (null terminated string of variable size) ("Author Name")
 * uint32 addon_version


 * struct file_table
 * uint32 file_number
 * char file_path (null terminated string of variable size)
 * uint64 file_size
 * uint32 file_crc


 * uint32 zero (0)


 * struct files
 * byte file (file data based on information from the file table)


 * uint32 addon_crc

Links

 * How to create and extract gma files
 * Source code for gmad to create and extract gma files