Play-/Source/IszImageStream.cpp

#include "IszImageStream.h"
#include <stdexcept>
#include <algorithm>
#include <string.h>
#include <assert.h>
#include "bzlib.h"
#include "zlib.h"
#include "StdStream.h"

CIszImageStream::CIszImageStream(CStream* baseStream)
    : m_baseStream(baseStream)
{
	if(baseStream == nullptr)
	{
		throw std::runtime_error("Null base stream supplied.");
	}

	baseStream->Read(&m_header, sizeof(HEADER));

	assert(m_header.hasPassword == 0);
	assert(m_header.segmentPtrOffset == 0);

	if(m_header.blockPtrOffset == 0)
	{
		throw std::runtime_error("Block Descriptor Table not present.");
	}
	if(m_header.blockPtrLength != 3)
	{
		throw std::runtime_error("Unsupported block descriptor size.");
	}

	ReadBlockDescriptorTable();
	m_cachedBlock = new uint8[m_header.blockSize];
	m_readBuffer = new uint8[m_header.blockSize];
}

CIszImageStream::~CIszImageStream()
{
	delete[] m_cachedBlock;
	delete[] m_readBuffer;
	delete[] m_blockDescriptorTable;
	delete m_baseStream;
}

void CIszImageStream::Seek(int64 position, Framework::STREAM_SEEK_DIRECTION origin)
{
	switch(origin)
	{
	case Framework::STREAM_SEEK_CUR:
		m_position += position;
		break;
	case Framework::STREAM_SEEK_SET:
		m_position = position;
		break;
	case Framework::STREAM_SEEK_END:
		m_position = GetTotalSize();
		break;
	}
}

uint64 CIszImageStream::Tell()
{
	return m_position;
}

uint64 CIszImageStream::Read(void* buffer, uint64 size)
{
	uint64 bytesRead = 0;
	uint8* inputBuffer = reinterpret_cast<uint8*>(buffer);
	while(size != 0)
	{
		if(IsEOF())
		{
			break;
		}
		SyncCache();
		uint64 blockPosition = (m_position % m_header.blockSize);
		uint64 sizeLeft = m_header.blockSize - blockPosition;
		uint64 sizeToRead = std::min<uint64>(size, sizeLeft);
		memcpy(inputBuffer, m_cachedBlock + blockPosition, static_cast<size_t>(sizeToRead));
		m_position += sizeToRead;
		size -= sizeToRead;
		inputBuffer += sizeToRead;
		bytesRead += sizeToRead;
	}
	return bytesRead;
}

uint64 CIszImageStream::Write(const void* buffer, uint64 size)
{
	throw std::exception();
}

bool CIszImageStream::IsEOF()
{
	return (m_position >= GetTotalSize());
}

void CIszImageStream::ReadBlockDescriptorTable()
{
	const char* key = "IsZ!";
	unsigned int cryptedTableLength = m_header.blockNumber * m_header.blockPtrLength;
	uint8* cryptedTable = new uint8[cryptedTableLength];
	m_baseStream->Seek(m_header.blockPtrOffset, Framework::STREAM_SEEK_SET);
	m_baseStream->Read(cryptedTable, cryptedTableLength);
	for(unsigned int i = 0; i < cryptedTableLength; i++)
	{
		cryptedTable[i] ^= ~key[i & 3];
	}

	m_blockDescriptorTable = new BLOCKDESCRIPTOR[m_header.blockNumber];
	for(unsigned int i = 0; i < m_header.blockNumber; i++)
	{
		uint32 value = *reinterpret_cast<uint32*>(&cryptedTable[i * m_header.blockPtrLength]);
		value &= 0xFFFFFF;
		m_blockDescriptorTable[i].size = value & 0x3FFFFF;
		m_blockDescriptorTable[i].storageType = static_cast<uint8>(value >> 22);
	}

	delete[] cryptedTable;
}

uint64 CIszImageStream::GetTotalSize() const
{
	return static_cast<uint64>(m_header.totalSectors) * static_cast<uint64>(m_header.sectorSize);
}

const CIszImageStream::BLOCKDESCRIPTOR& CIszImageStream::SeekToBlock(uint64 blockNumber)
{
	assert(blockNumber < m_header.blockNumber);
	uint64 seekPosition = m_header.dataOffset;
	for(unsigned int i = 0; i < blockNumber; i++)
	{
		const BLOCKDESCRIPTOR& blockDescriptor = m_blockDescriptorTable[i];
		if(blockDescriptor.storageType != ADI_ZERO)
		{
			seekPosition += blockDescriptor.size;
		}
	}
	m_baseStream->Seek(seekPosition, Framework::STREAM_SEEK_SET);
	return m_blockDescriptorTable[blockNumber];
}

void CIszImageStream::SyncCache()
{
	uint64 currentSector = (m_position / m_header.sectorSize);
	uint64 neededBlock = (currentSector * m_header.sectorSize) / m_header.blockSize;
	if(neededBlock == m_cachedBlockNumber)
	{
		return;
	}
	if(neededBlock >= m_header.blockNumber)
	{
		throw std::runtime_error("Trying to read past eof.");
	}

	const BLOCKDESCRIPTOR& blockDescriptor = SeekToBlock(neededBlock);
	memset(m_cachedBlock, 0, m_header.blockSize);
	switch(blockDescriptor.storageType)
	{
	case ADI_ZERO:
		ReadZeroBlock(blockDescriptor.size);
		break;
	case ADI_DATA:
		ReadDataBlock(blockDescriptor.size);
		break;
	case ADI_ZLIB:
		ReadGzipBlock(blockDescriptor.size);
		break;
	case ADI_BZ2:
		ReadBz2Block(blockDescriptor.size);
		break;
	default:
		throw std::runtime_error("Unsupported block storage mode.");
		break;
	}
	m_cachedBlockNumber = neededBlock;
}

void CIszImageStream::ReadZeroBlock(uint32 compressedBlockSize)
{
	if(compressedBlockSize != m_header.blockSize)
	{
		throw std::runtime_error("Invalid zero block.");
	}
}

void CIszImageStream::ReadDataBlock(uint32 compressedBlockSize)
{
	if(compressedBlockSize != m_header.blockSize)
	{
		throw std::runtime_error("Invalid data block.");
	}
	m_baseStream->Read(m_cachedBlock, compressedBlockSize);
}

void CIszImageStream::ReadGzipBlock(uint32 compressedBlockSize)
{
	m_baseStream->Read(m_readBuffer, compressedBlockSize);
	uLongf destLength = m_header.blockSize;
	if(uncompress(
	       reinterpret_cast<Bytef*>(m_cachedBlock), &destLength,
	       reinterpret_cast<Bytef*>(m_readBuffer), compressedBlockSize) != Z_OK)
	{
		throw std::runtime_error("Error decompressing zlib block.");
	}
}

void CIszImageStream::ReadBz2Block(uint32 compressedBlockSize)
{
	m_baseStream->Read(m_readBuffer, compressedBlockSize);
	//Force BZ2 header
	m_readBuffer[0] = 'B';
	m_readBuffer[1] = 'Z';
	m_readBuffer[2] = 'h';
	unsigned int destLength = m_header.blockSize;
	if(BZ2_bzBuffToBuffDecompress(
	       reinterpret_cast<char*>(m_cachedBlock), &destLength,
	       reinterpret_cast<char*>(m_readBuffer), compressedBlockSize, 0, 0) != BZ_OK)
	{
		throw std::runtime_error("Error decompressing bz2 block.");
	}
}