Mercurial > vba-linux

     1 // FindSignature.cpp

     2 

     3 #include "StdAfx.h"

     4 

     5 #include "Common/Buffer.h"

     6 

     7 #include "FindSignature.h"

     8 

     9 #include "../../Common/StreamUtils.h"

    10 

    11 HRESULT FindSignatureInStream(ISequentialInStream *stream,

    12     const Byte *signature, unsigned signatureSize,

    13     const UInt64 *limit, UInt64 &resPos)

    14 {

    15   resPos = 0;

    16   CByteBuffer byteBuffer2;

    17   byteBuffer2.SetCapacity(signatureSize);

    18   RINOK(ReadStream_FALSE(stream, byteBuffer2, signatureSize));

    19 

    20   if (memcmp(byteBuffer2, signature, signatureSize) == 0)

    21     return S_OK;

    22 

    23   const UInt32 kBufferSize = (1 << 16);

    24   CByteBuffer byteBuffer;

    25   byteBuffer.SetCapacity(kBufferSize);

    26   Byte *buffer = byteBuffer;

    27   UInt32 numPrevBytes = signatureSize - 1;

    28   memcpy(buffer, (const Byte *)byteBuffer2 + 1, numPrevBytes);

    29   resPos = 1;

    30   for (;;)

    31   {

    32     if (limit != NULL)

    33       if (resPos > *limit)

    34         return S_FALSE;

    35     do

    36     {

    37       UInt32 numReadBytes = kBufferSize - numPrevBytes;

    38       UInt32 processedSize;

    39       RINOK(stream->Read(buffer + numPrevBytes, numReadBytes, &processedSize));

    40       numPrevBytes += processedSize;

    41       if (processedSize == 0)

    42         return S_FALSE;

    43     }

    44     while (numPrevBytes < signatureSize);

    45     UInt32 numTests = numPrevBytes - signatureSize + 1;

    46     for (UInt32 pos = 0; pos < numTests; pos++)

    47     {

    48       Byte b = signature[0];

    49       for (; buffer[pos] != b && pos < numTests; pos++);

    50       if (pos == numTests)

    51         break;

    52       if (memcmp(buffer + pos, signature, signatureSize) == 0)

    53       {

    54         resPos += pos;

    55         return S_OK;

    56       }

    57     }

    58     resPos += numTests;

    59     numPrevBytes -= numTests;

    60     memmove(buffer, buffer + numTests, numPrevBytes);

    61   }

    62 }
author	Robert McIntyre <rlm@mit.edu>
date	Sat, 03 Mar 2012 10:31:27 -0600
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