63 lines
1.6 KiB
C++
63 lines
1.6 KiB
C++
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// FindSignature.cpp
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#include "StdAfx.h"
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#include <string.h>
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#include "../../../Common/MyBuffer.h"
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#include "../../Common/StreamUtils.h"
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#include "FindSignature.h"
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HRESULT FindSignatureInStream(ISequentialInStream *stream,
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const Byte *signature, unsigned signatureSize,
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const UInt64 *limit, UInt64 &resPos)
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{
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resPos = 0;
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CByteBuffer byteBuffer2(signatureSize);
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RINOK(ReadStream_FALSE(stream, byteBuffer2, signatureSize));
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if (memcmp(byteBuffer2, signature, signatureSize) == 0)
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return S_OK;
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const UInt32 kBufferSize = (1 << 16);
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CByteBuffer byteBuffer(kBufferSize);
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Byte *buffer = byteBuffer;
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UInt32 numPrevBytes = signatureSize - 1;
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memcpy(buffer, (const Byte *)byteBuffer2 + 1, numPrevBytes);
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resPos = 1;
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for (;;)
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{
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if (limit != NULL)
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if (resPos > *limit)
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return S_FALSE;
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do
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{
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UInt32 numReadBytes = kBufferSize - numPrevBytes;
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UInt32 processedSize;
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RINOK(stream->Read(buffer + numPrevBytes, numReadBytes, &processedSize));
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numPrevBytes += processedSize;
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if (processedSize == 0)
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return S_FALSE;
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}
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while (numPrevBytes < signatureSize);
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UInt32 numTests = numPrevBytes - signatureSize + 1;
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for (UInt32 pos = 0; pos < numTests; pos++)
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{
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Byte b = signature[0];
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for (; buffer[pos] != b && pos < numTests; pos++);
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if (pos == numTests)
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break;
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if (memcmp(buffer + pos, signature, signatureSize) == 0)
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{
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resPos += pos;
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return S_OK;
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}
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}
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resPos += numTests;
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numPrevBytes -= numTests;
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memmove(buffer, buffer + numTests, numPrevBytes);
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}
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}
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