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