Garry's Mod Addon
From Just Solve the File Format Problem
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 created from a folder, or extracted into a hierarchy of folders.
Format
char[4] ident ("GMAD")
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
