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https://github.com/libretro/Play-.git
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98 lines
2.8 KiB
C++
98 lines
2.8 KiB
C++
#include <cassert>
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#include <cstring>
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#include "OpticalMedia.h"
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#define DVD_LAYER_MAX_BLOCKS 2295104
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COpticalMedia::COpticalMedia(const StreamPtr& stream)
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{
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//Simulate a disk with only one data track
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try
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{
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auto blockProvider = std::make_shared<ISO9660::CBlockProvider2048>(stream);
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m_fileSystem = std::make_unique<CISO9660>(blockProvider);
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m_track0DataType = TRACK_DATA_TYPE_MODE1_2048;
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}
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catch(...)
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{
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//Failed with block size 2048, try with CD-ROM XA
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auto blockProvider = std::make_shared<ISO9660::CBlockProviderCDROMXA>(stream);
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m_fileSystem = std::make_unique<CISO9660>(blockProvider);
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m_track0DataType = TRACK_DATA_TYPE_MODE2_2352;
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}
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if(m_track0DataType == TRACK_DATA_TYPE_MODE1_2048)
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{
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CheckDualLayerDvd(stream);
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}
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}
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COpticalMedia::TRACK_DATA_TYPE COpticalMedia::GetTrackDataType(uint32 trackIndex) const
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{
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assert(trackIndex == 0);
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return m_track0DataType;
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}
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CISO9660* COpticalMedia::GetFileSystem()
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{
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return m_fileSystem.get();
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}
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bool COpticalMedia::GetDvdIsDualLayer() const
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{
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return m_dvdIsDualLayer;
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}
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uint32 COpticalMedia::GetDvdSecondLayerStart() const
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{
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return m_dvdSecondLayerStart;
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}
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void COpticalMedia::CheckDualLayerDvd(const StreamPtr& stream)
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{
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//Heuristic to detect dual layer DVD disc images
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static const uint32 blockSize = 2048;
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auto imageSize = stream->GetLength();
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uint32 imageBlockCount = static_cast<uint32>(imageSize / blockSize);
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//DL discs may be smaller than the capacity of a SL DVD, but we assume
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//that games that use DL discs use more than the SL DVD capacity
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if(imageBlockCount < DVD_LAYER_MAX_BLOCKS) return;
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//Bigger than the capacity of a SL DVD, certainly a dual layer disc
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m_dvdIsDualLayer = true;
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//We need to look for the start of the second layer
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//The second layer is at most as big as the first one, so
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//we can start looking from half of the disk image
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//NOTE: Wild Arms: Alter Code F seems to have a second layer that's a bit
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//larger than the first one? That's why we start looking at 15 / 32 of the image's size
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auto searchBlockAddress = imageBlockCount * 15 / 32;
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stream->Seek(static_cast<uint64>(searchBlockAddress) * blockSize, Framework::STREAM_SEEK_SET);
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//Scan all blocks from the search point, looking for a valid ISO9660 descriptor
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for(auto lba = searchBlockAddress; lba < imageBlockCount; lba++)
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{
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static const uint32 blockHeaderSize = 6;
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static_assert(blockSize >= blockHeaderSize, "Block header size is too large");
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char blockHeader[blockHeaderSize];
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stream->Read(blockHeader, blockHeaderSize);
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if(
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(blockHeader[0] == 0x01) &&
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(!strncmp(blockHeader + 1, "CD001", 5))
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)
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{
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//We've found a valid ISO9660 descriptor
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m_dvdSecondLayerStart = lba;
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break;
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}
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stream->Seek(blockSize - blockHeaderSize, Framework::STREAM_SEEK_CUR);
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}
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//If we haven't found it, something's wrong
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assert(m_dvdSecondLayerStart != 0);
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}
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