101 lines
2.0 KiB
C++
101 lines
2.0 KiB
C++
// CabBlockInStream.cpp
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#include "StdAfx.h"
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#include "../../../../C/Alloc.h"
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#include "../../../../C/CpuArch.h"
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#include "../../Common/StreamUtils.h"
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#include "CabBlockInStream.h"
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namespace NArchive {
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namespace NCab {
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static const UInt32 kBlockSize = (1 << 16);
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bool CCabBlockInStream::Create()
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{
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if (!_buf)
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_buf = (Byte *)::MyAlloc(kBlockSize);
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return _buf != 0;
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}
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CCabBlockInStream::~CCabBlockInStream()
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{
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::MyFree(_buf);
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}
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static UInt32 CheckSum(const Byte *p, UInt32 size)
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{
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UInt32 sum = 0;
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for (; size >= 8; size -= 8)
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{
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sum ^= GetUi32(p) ^ GetUi32(p + 4);
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p += 8;
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}
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if (size >= 4)
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{
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sum ^= GetUi32(p);
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p += 4;
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}
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size &= 3;
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if (size > 2) sum ^= (UInt32)(*p++) << 16;
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if (size > 1) sum ^= (UInt32)(*p++) << 8;
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if (size > 0) sum ^= (UInt32)(*p++);
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return sum;
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}
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HRESULT CCabBlockInStream::PreRead(ISequentialInStream *stream, UInt32 &packSize, UInt32 &unpackSize)
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{
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const UInt32 kHeaderSize = 8;
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const UInt32 kReservedMax = 256;
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Byte header[kHeaderSize + kReservedMax];
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RINOK(ReadStream_FALSE(stream, header, kHeaderSize + ReservedSize))
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packSize = GetUi16(header + 4);
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unpackSize = GetUi16(header + 6);
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if (packSize > kBlockSize - _size)
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return S_FALSE;
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RINOK(ReadStream_FALSE(stream, _buf + _size, packSize));
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if (MsZip)
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{
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if (_size == 0)
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{
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if (packSize < 2 || _buf[0] != 0x43 || _buf[1] != 0x4B)
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return S_FALSE;
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_pos = 2;
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}
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if (_size + packSize > ((UInt32)1 << 15) + 12) /* v9.31 fix. MSZIP specification */
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return S_FALSE;
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}
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if (GetUi32(header) != 0) // checkSum
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if (CheckSum(header, kHeaderSize + ReservedSize) != CheckSum(_buf + _size, packSize))
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return S_FALSE;
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_size += packSize;
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return S_OK;
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}
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STDMETHODIMP CCabBlockInStream::Read(void *data, UInt32 size, UInt32 *processedSize)
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{
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if (size != 0)
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{
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UInt32 rem = _size - _pos;
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if (size > rem)
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size = rem;
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memcpy(data, _buf + _pos, size);
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_pos += size;
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}
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if (processedSize)
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*processedSize = size;
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return S_OK;
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}
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}}
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