DiscIO: Add functions CreateDisc and CreateWAD

...in addition to the existing function CreateVolume
(renamed from CreateVolumeFromFilename).

Lets code easily add constraints such as not letting the user
select a WAD file when using the disc changing functionality.

Source/Core/DiscIO/CompressedBlob.cpp

@@ -182,10 +182,10 @@ bool CompressFileToBlob(const std::string& infile_path, const std::string& outfi
   }
 
   DiscScrubber disc_scrubber;
-  std::unique_ptr<Volume> volume;
+  std::unique_ptr<VolumeDisc> volume;
   if (sub_type == 1)
   {
-    volume = CreateVolumeFromFilename(infile_path);
+    volume = CreateDisc(infile_path);
     if (!volume || !disc_scrubber.SetupScrub(volume.get(), block_size))
     {
       PanicAlertT("\"%s\" failed to be scrubbed. Probably the image is corrupt.",

Source/Core/DiscIO/FileSystemGCWii.cpp

@@ -223,7 +223,7 @@ bool FileInfoGCWii::IsValid(u64 fst_size, const FileInfoGCWii& parent_directory)
   return true;
 }
 
-FileSystemGCWii::FileSystemGCWii(const Volume* volume, const Partition& partition)
+FileSystemGCWii::FileSystemGCWii(const VolumeDisc* volume, const Partition& partition)
     : m_valid(false), m_root(nullptr, 0, 0, 0)
 {
   u8 offset_shift;

Source/Core/DiscIO/FileSystemGCWii.h

@@ -17,7 +17,7 @@
 
 namespace DiscIO
 {
-class Volume;
+class VolumeDisc;
 struct Partition;
 
 class FileInfoGCWii : public FileInfo
@@ -87,7 +87,7 @@ private:
 class FileSystemGCWii : public FileSystem
 {
 public:
-  FileSystemGCWii(const Volume* volume, const Partition& partition);
+  FileSystemGCWii(const VolumeDisc* volume, const Partition& partition);
   ~FileSystemGCWii() override;
 
   bool IsValid() const override { return m_valid; }

Source/Core/DiscIO/Volume.cpp

@@ -43,23 +43,13 @@ std::map<Language, std::string> Volume::ReadWiiNames(const std::vector<char16_t>
   return names;
 }
 
-std::unique_ptr<Volume> CreateVolumeFromFilename(const std::string& filename)
+static std::unique_ptr<VolumeDisc> CreateDisc(std::unique_ptr<BlobReader>& reader)
 {
-  std::unique_ptr<BlobReader> reader(CreateBlobReader(filename));
-  if (reader == nullptr)
-    return nullptr;
-
   // Check for Wii
   const std::optional<u32> wii_magic = reader->ReadSwapped<u32>(0x18);
   if (wii_magic == u32(0x5D1C9EA3))
     return std::make_unique<VolumeWii>(std::move(reader));
 
-  // Check for WAD
-  // 0x206962 for boot2 wads
-  const std::optional<u32> wad_magic = reader->ReadSwapped<u32>(0x02);
-  if (wad_magic == u32(0x00204973) || wad_magic == u32(0x00206962))
-    return std::make_unique<VolumeWAD>(std::move(reader));
-
   // Check for GC
   const std::optional<u32> gc_magic = reader->ReadSwapped<u32>(0x1C);
   if (gc_magic == u32(0xC2339F3D))
@@ -69,4 +59,45 @@ std::unique_ptr<Volume> CreateVolumeFromFilename(const std::string& filename)
   return nullptr;
 }
 
+std::unique_ptr<VolumeDisc> CreateDisc(const std::string& path)
+{
+  std::unique_ptr<BlobReader> reader(CreateBlobReader(path));
+  return reader ? CreateDisc(reader) : nullptr;
+}
+
+static std::unique_ptr<VolumeWAD> CreateWAD(std::unique_ptr<BlobReader>& reader)
+{
+  // Check for WAD
+  // 0x206962 for boot2 wads
+  const std::optional<u32> wad_magic = reader->ReadSwapped<u32>(0x02);
+  if (wad_magic == u32(0x00204973) || wad_magic == u32(0x00206962))
+    return std::make_unique<VolumeWAD>(std::move(reader));
+
+  // No known magic words found
+  return nullptr;
+}
+
+std::unique_ptr<VolumeWAD> CreateWAD(const std::string& path)
+{
+  std::unique_ptr<BlobReader> reader(CreateBlobReader(path));
+  return reader ? CreateWAD(reader) : nullptr;
+}
+
+std::unique_ptr<Volume> CreateVolume(const std::string& path)
+{
+  std::unique_ptr<BlobReader> reader(CreateBlobReader(path));
+  if (reader == nullptr)
+    return nullptr;
+
+  std::unique_ptr<VolumeDisc> disc = CreateDisc(reader);
+  if (disc)
+    return disc;
+
+  std::unique_ptr<VolumeWAD> wad = CreateWAD(reader);
+  if (wad)
+    return wad;
+
+  return nullptr;
+}
+
 }  // namespace DiscIO

Source/Core/DiscIO/Volume.h

@@ -22,6 +22,7 @@ namespace DiscIO
 {
 enum class BlobType;
 class FileSystem;
+class VolumeWAD;
 
 struct Partition final
 {
@@ -141,6 +142,12 @@ protected:
   static const std::vector<u8> INVALID_CERT_CHAIN;
 };
 
-std::unique_ptr<Volume> CreateVolumeFromFilename(const std::string& filename);
+class VolumeDisc : public Volume
+{
+};
+
+std::unique_ptr<VolumeDisc> CreateDisc(const std::string& path);
+std::unique_ptr<VolumeWAD> CreateWAD(const std::string& path);
+std::unique_ptr<Volume> CreateVolume(const std::string& path);
 
 }  // namespace DiscIO

Source/Core/DiscIO/VolumeGC.h

@@ -25,7 +25,7 @@ enum class Language;
 enum class Region;
 enum class Platform;
 
-class VolumeGC : public Volume
+class VolumeGC : public VolumeDisc
 {
 public:
   VolumeGC(std::unique_ptr<BlobReader> reader);

Source/Core/DiscIO/VolumeWii.h

@@ -27,7 +27,7 @@ enum class Language;
 enum class Region;
 enum class Platform;
 
-class VolumeWii : public Volume
+class VolumeWii : public VolumeDisc
 {
 public:
   VolumeWii(std::unique_ptr<BlobReader> reader);