Add TGC disc image compatibility

Source/Core/DiscIO/TGCBlob.cpp

@@ -0,0 +1,141 @@
+// Copyright 2016 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <memory>
+#include <string>
+
+#include "Common/CommonFuncs.h"
+#include "Common/FileUtil.h"
+#include "DiscIO/TGCBlob.h"
+
+namespace
+{
+template <typename T>
+struct Interval
+{
+  T start;
+  T length;
+
+  T End() const { return start + length; }
+  bool IsEmpty() const { return length == 0; }
+};
+
+template <typename T>
+void SplitInterval(T split_point, Interval<T> interval, Interval<T>* out_1, Interval<T>* out_2)
+{
+  if (interval.start < split_point)
+    *out_1 = {interval.start, std::min(interval.length, split_point - interval.start)};
+  else
+    *out_1 = {0, 0};
+
+  if (interval.End() > split_point)
+    *out_2 = {std::max(interval.start, split_point),
+              std::min(interval.length, interval.End() - split_point)};
+  else
+    *out_2 = {0, 0};
+}
+
+u32 SubtractBE32(u32 minuend_be, u32 subtrahend_le)
+{
+  return Common::swap32(Common::swap32(minuend_be) - subtrahend_le);
+}
+
+void Replace8(u64 offset, u64 nbytes, u8* out_ptr, u64 replace_offset, u8 replace_value)
+{
+  if (offset <= replace_offset && offset + nbytes > replace_offset)
+    out_ptr[replace_offset - offset] = replace_value;
+}
+
+void Replace32(u64 offset, u64 nbytes, u8* out_ptr, u64 replace_offset, u32 replace_value)
+{
+  for (size_t i = 0; i < sizeof(u32); ++i)
+    Replace8(offset, nbytes, out_ptr, replace_offset + i, reinterpret_cast<u8*>(&replace_value)[i]);
+}
+}
+
+namespace DiscIO
+{
+bool IsTGCBlob(const std::string& path)
+{
+  File::IOFile file(path, "rb");
+
+  TGCHeader header;
+  return (file.ReadArray(&header, 1) && header.magic == Common::swap32(0xAE0F38A2));
+}
+
+std::unique_ptr<TGCFileReader> TGCFileReader::Create(const std::string& path)
+{
+  if (IsTGCBlob(path))
+  {
+    File::IOFile file(path, "rb");
+    return std::unique_ptr<TGCFileReader>(new TGCFileReader(std::move(file)));
+  }
+
+  return nullptr;
+}
+
+TGCFileReader::TGCFileReader(File::IOFile&& file) : m_file(std::move(file))
+{
+  m_file.ReadArray(&m_header, 1);
+  u32 header_size = Common::swap32(m_header.header_size);
+  m_size = m_file.GetSize();
+  m_file_offset = Common::swap32(m_header.unknown_important_2) -
+                  Common::swap32(m_header.unknown_important_1) + header_size;
+}
+
+u64 TGCFileReader::GetDataSize() const
+{
+  return m_size + Common::swap32(m_header.unknown_important_2) -
+         Common::swap32(m_header.unknown_important_1);
+}
+
+bool TGCFileReader::Read(u64 offset, u64 nbytes, u8* out_ptr)
+{
+  Interval<u64> first_part;
+  Interval<u64> empty_part;
+  Interval<u64> last_part;
+
+  u32 header_size = Common::swap32(m_header.header_size);
+  SplitInterval(m_file_offset, Interval<u64>{offset, nbytes}, &first_part, &last_part);
+  SplitInterval(m_size - header_size, first_part, &first_part, &empty_part);
+
+  // Offsets before m_file_offset are read as usual
+  if (!first_part.IsEmpty())
+  {
+    if (!InternalRead(first_part.start, first_part.length, out_ptr + (first_part.start - offset)))
+      return false;
+  }
+
+  // If any offset before m_file_offset isn't actually in the file,
+  // treat it as 0x00 bytes (so e.g. MD5 calculation of the whole disc won't fail)
+  if (!empty_part.IsEmpty())
+    std::fill_n(out_ptr + (empty_part.start - offset), empty_part.length, 0);
+
+  // Offsets after m_file_offset are read as if they are (offset - m_file_offset)
+  if (!last_part.IsEmpty())
+  {
+    if (!InternalRead(last_part.start - m_file_offset, last_part.length,
+                      out_ptr + (last_part.start - offset)))
+      return false;
+  }
+
+  return true;
+}
+
+bool TGCFileReader::InternalRead(u64 offset, u64 nbytes, u8* out_ptr)
+{
+  u32 header_size = Common::swap32(m_header.header_size);
+
+  if (m_file.Seek(offset + header_size, SEEK_SET) && m_file.ReadBytes(out_ptr, nbytes))
+  {
+    Replace32(offset, nbytes, out_ptr, 0x420, SubtractBE32(m_header.dol_offset, header_size));
+    Replace32(offset, nbytes, out_ptr, 0x424, SubtractBE32(m_header.fst_offset, header_size));
+    return true;
+  }
+
+  m_file.Clear();
+  return false;
+}
+
+}  // namespace DiscIO