# gcmtool.py

Python3 script for unpack/pack/rebuild GCM/iso file format. This tool can rebuild FileStringTable (FST) of GCM and patch boot.bin with a new apploader.img, boot.dol, add/remove/edit folder and files of the game. MIT License.

## User manual

Unpack GCM/iso file **source_gcm.iso** in the default new folder _game_code-DVD_number_. If optional_dest_folder is specified we unpack in _optional_dest_folder_.
```
gcmtool.py --unpack source_gcm.iso optional_dest_folder
```
Pack **source_folder** in the default new GCM/iso file _source_folder.iso_. If optional_dest_file.iso is specified we pack in _optional_dest_file.iso_. If one of the files or system files contains length change we have to use --rebuild-fst command before packing. If the dol is duplicated in the FST use --disable-ignore to allow shared dol space.  If conf is enabled it will have priority on system values.
```
gcmtool.py --pack source_folder optional_dest_file.iso
```
Rebuild the FST file system of an unpacked GCM/iso and patch boot.bin for a new apploader, dol, and add/remove/edit of folders and files. If conf is enabled it will have priority on system values.
```
gcmtool.py --rebuild-fst source_folder
```
Print stats about the GCM/iso file or the unpacked GCM/iso folder. This stats contains informations about full memory mapping sorted by offset (files and system files), get empty spaces informations using optional align -a (default=4) and all conf values.
```
gcmtool.py --stats path -a 4 
```
Unpack and rebuild the FST of the unpacked folder.
```
gcmtool.py -ur source_gcm.iso optional_dest_folder
```
Rebuild the FST of the unpacked folder and pack.
```
gcmtool.py -rp source_folder optional_dest_file.iso
```
Japanese charset is not handled for now except if you have installed Japanese local.

The original GCM/iso and repack GCM/iso are different most of the time. This is because GCM DVD contains "empty spaces" with data unused (old datas or random datas I don't know). So this datas are useless and loss during unpack.

The sorting of files during FST rebuild is deferent from the original and this is full compatible with the GameCube dol API.

## Extracted file tree

root folder contains all files of the unpacked GCM/iso

sys folder contains GCM system files of the game:
* boot.bin
* bi2.bin
* apploader.img
* boot.dol
* fst.bin
* system.conf

## sys/sytem.conf

The conf file system.conf allow to force somes values and patch sys/files and also new generated iso. The conf file is parsed and applied with --pack and --rebuild-fst.

### [Default]

* **boot.bin_section** = disabled / enabled # If enabled then boot.bin section will be applied.
* **bi2.bin_section** = disabled / enabled # If enabled then bi2.bin section will be applied.
* **apploader.img_section** = disabled / enabled # If enabled then apploader.img section will be applied.

### [boot.bin]

* **GameCode** = GG4P _# 4 bytes ascii value - A-Za-z0-9_
* **MakerCode** = 08 _# 2 bytes ascii value - A-Za-z0-9_
* **DiscNumber** = 0 _# Disc number information for multiple discs. The number starts from 0. 0-98_
* **GameVersion** = 0 _# The version number of the video game. 0-99_
* **AudioStreaming** = 1 _# The flag for the streaming mode. 1 for streaming mode, otherwise 0._
* **StreamBufferSize** = 0 _# Number of Streaming buffers. 0-15_
* **DVDMagic** = 0xc2339f3d
* **GameName** = GotchaForceEur _# The character string of the video game title (Kanji characters are available.). 64 bytes max._
* **DolOffset** = auto _# Hex value: 0xabcdef or auto: dol offset on the DVD._
* **FstOffset** = auto _# Hex value: 0xabcdef or auto: fst offset on the DVD._
* **FstLen** = auto _# Hex value: 0xabcdef or auto: fst length._
* **FstMaxLen** = auto _# Hex value: 0xabcdef or auto: the size of the area reserved for FST. Used when there is multiple FST to load (multiple DVD)._
* **UserPosition** = auto _# Hex value: 0xabcdef or auto: start of files stored in the gcm._
* **UserLength** = auto _# Hex value: 0xabcdef or auto: length of files stored in the gcm._

### [bi2.bin]

* **DebugMonitorSize** = 0x0 _# Hex value: 0xabcdef aligned to 32 bytes._
* **SimulatedMemorySize** = 0x1800000 _# Hex value: 0xabcdef aligned to 32 bytes._
* **ArgumentOffset** = 0x0 _# Hex value: 0xabcdef_
* **DebugFlag** = 0 _# Numeric value: 123. Following values could change._
  * **0,1,5,6,7**: normal boot
  * **2**: Devkit set to : 0, MetroTRK : Set to AMC DDH hardware
  * **3**: Devkit set to : 1, MetroTRK : Set to GDEV hardware
  * **4**: Devkit set to : 2, MetroTRK : Set to BBA
* **TrackLocation** = 0x0 _# Hex value: 0xabcdef_
* **TrackSize** = 0x0 _# Hex value: 0xabcdef_
* **CountryCode** = 2 _# Numeric value: 123 - Japan=0, USA=1, PAL=2, SouthKorea=4_
* **TotalDisc** = 1 _# Numeric value: 1-99_
* **LongFileNameSupport** = 1 _# Numeric value. Set to 1 for long file name support; set to 0 to restrict file to 8.3 format._
* **DolLimit** = 0x0 _# Hex value: 0xabcdef_

### [apploader.img]

* **Version** = 2003/04/17 _# 16 bytes ascii_
* **EntryPoint** = 0x81200258 _# Hex value: 0xabcdef_
* **Size** = 0x1954 _# Hex value: 0xabcdef_
* **TrailerSize** = 0x1b8b0 _# Hex value: 0xabcdef_