[libromdata] CisoGcnReader: IDiscReader class for GCN/Wii CISO files.

This is a sparse image format supported by Dolphin and a few USB loaders.
Not nearly as common as WBFS, though.

This CISO is also unrelated to the PSP CISO format, which has zlib
compression in addition to sparse.

NOTE: isRomSupported() can't determine the system type, since the disc
header is at $8000, so it sets the system type to unknown while setting
format to CISO. In this case, the GameCube constructor will check the
magic values itself to determine the actual system.

Added file extensions ".ciso" and ".cso".

TODO:
- Write an IDiscReaderFactory class to auto-detect the different types
  of disc image formats and return an IDiscReader.
- Add support for Dolphin GCZ images. (requires zlib)
- Maybe add support for PSP CISO images later, if I ever implement
  support for PSP disc images.

src/libromdata/CMakeLists.txt

@@ -80,6 +80,7 @@ SET(libromdata_SRCS
 	img/RpImageLoader.cpp
 	disc/DiscReader.cpp
 	disc/WbfsReader.cpp
+	disc/CisoGcnReader.cpp
 	disc/GcnPartition.cpp
 	disc/GcnPartitionPrivate.cpp
 	disc/WiiPartition.cpp
@@ -118,6 +119,8 @@ SET(libromdata_H
 	disc/IDiscReader.hpp
 	disc/DiscReader.hpp
 	disc/WbfsReader.hpp
+	disc/CisoGcnReader.hpp
+	disc/ciso_gcn.h
 	disc/IPartition.hpp
 	disc/GcnPartition.hpp
 	disc/GcnPartitionPrivate.hpp

src/libromdata/GameCube.cpp

@@ -31,6 +31,7 @@
 // DiscReader
 #include "disc/DiscReader.hpp"
 #include "disc/WbfsReader.hpp"
+#include "disc/CisoGcnReader.hpp"
 #include "disc/WiiPartition.hpp"
 
 // C includes. (C++ namespace)
@@ -81,6 +82,7 @@ class GameCubePrivate
 			// High byte: Image format.
 			DISC_FORMAT_RAW  = (0 << 8),	// Raw image. (ISO, GCM)
 			DISC_FORMAT_WBFS = (1 << 8),	// WBFS image. (Wii only)
+			DISC_FORMAT_CISO = (2 << 8),	// CISO image.
 			DISC_FORMAT_UNKNOWN = (0xFF << 8),
 			DISC_FORMAT_MASK = (0xFF << 8),
 		};
@@ -499,6 +501,9 @@ GameCube::GameCube(IRpFile *file)
 			case GameCubePrivate::DISC_FORMAT_WBFS:
 				d->discReader = new WbfsReader(m_file);
 				break;
+			case GameCubePrivate::DISC_FORMAT_CISO:
+				d->discReader = new CisoGcnReader(m_file);
+				break;
 			case GameCubePrivate::DISC_FORMAT_UNKNOWN:
 			default:
 				d->discType = GameCubePrivate::DISC_UNKNOWN;
@@ -517,6 +522,33 @@ GameCube::GameCube(IRpFile *file)
 			d->discReader = nullptr;
 			d->discType = GameCubePrivate::DISC_UNKNOWN;
 			m_isValid = false;
+			return;
+		}
+
+		if (d->discType != GameCubePrivate::DISC_UNKNOWN &&
+		    ((d->discType & GameCubePrivate::DISC_SYSTEM_MASK) == GameCubePrivate::DISC_SYSTEM_UNKNOWN))
+		{
+			// isRomSupported() was unable to determine the
+			// system type, possibly due to format limitations.
+			// Example: CISO doesn't store a copy of the disc header
+			// in range of the data we read.
+			if (be32_to_cpu(d->discHeader.magic_wii) == WII_MAGIC) {
+				// Wii disc image.
+				d->discType &= ~GameCubePrivate::DISC_SYSTEM_MASK;
+				d->discType |=  GameCubePrivate::DISC_SYSTEM_WII;
+			} else if (be32_to_cpu(d->discHeader.magic_gcn) == GCN_MAGIC) {
+				// GameCube disc image.
+				// TODO: Check for Triforce?
+				d->discType &= ~GameCubePrivate::DISC_SYSTEM_MASK;
+				d->discType |=  GameCubePrivate::DISC_SYSTEM_GCN;
+			} else {
+				// Unknown system type.
+				delete d->discReader;
+				d->discReader = nullptr;
+				d->discType = GameCubePrivate::DISC_UNKNOWN;
+				m_isValid = false;
+				return;
+			}
 		}
 	}
 }
@@ -587,6 +619,14 @@ int GameCube::isRomSupported_static(const DetectInfo *info)
 		}
 	}
 
+	// Check for CISO.
+	if (CisoGcnReader::isDiscSupported_static(info->pHeader, info->szHeader) >= 0) {
+		// CISO format doesn't store a copy of the disc header
+		// at the beginning of the disc, so we can't check the
+		// system format here.
+		return GameCubePrivate::DISC_SYSTEM_UNKNOWN | GameCubePrivate::DISC_FORMAT_CISO;
+	}
+
 	// Not supported.
 	return GameCubePrivate::DISC_UNKNOWN;
 }
@@ -648,10 +688,12 @@ vector<const rp_char*> GameCube::supportedFileExtensions_static(void)
 {
 	// TODO: Add ".iso" later? (Too generic, though...)
 	vector<const rp_char*> ret;
-	ret.reserve(3);
+	ret.reserve(5);
 	ret.push_back(_RP(".gcm"));
 	ret.push_back(_RP(".rvm"));
 	ret.push_back(_RP(".wbfs"));
+	ret.push_back(_RP(".ciso"));
+	ret.push_back(_RP(".cso"));
 	return ret;
 }