Method _read

Engine/source/core/stream/fileStream.cpp:243–341

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bool FileStream::_read(const U32 i_numBytes, void *o_pBuffer)
{
   AssertFatal(0 != mStreamCaps, "FileStream::_read: the stream isn't open");
   AssertFatal(NULL != o_pBuffer || i_numBytes == 0, "FileStream::_read: NULL destination pointer with non-zero read request");

   if (!hasCapability(Stream::StreamRead))
   {
      AssertFatal(false, "FileStream::_read: file stream lacks capability");
      Stream::setStatus(IllegalCall);
      return(false);
   }

   // exit on pre-existing errors
   if (Ok != getStatus())
      return(false);

   // if a request of non-zero length was made
   if (0 != i_numBytes)
   {
      U8 *pDst = (U8 *)o_pBuffer;
      U32 readSize;
      U32 remaining = i_numBytes;
      U32 bytesRead;
      U32 blockHead;
      U32 blockTail;

      // check if the buffer has some data in it
      if (BUFFER_INVALID != mBuffHead)
      {
         // copy as much as possible from the buffer into the destination
         readSize = ((mBuffTail + 1) >= mBuffPos) ? (mBuffTail + 1 - mBuffPos) : 0;
         readSize = getMin(readSize, remaining);
         calcBlockHead(mBuffPos, &blockHead);
         dMemcpy(pDst, mBuffer + (mBuffPos - blockHead), readSize);
         // reduce the remaining amount to read
         remaining -= readSize;
         // advance the buffer pointers
         mBuffPos += readSize;
         pDst += readSize;

         if (mBuffPos > mBuffTail && remaining != 0)
         {
            flush();
            mBuffHead = BUFFER_INVALID;
            if (mEOF == true)
               Stream::setStatus(EOS);
         }
      }

      // if the request wasn't satisfied by the buffer and the file has more data
      if (false == mEOF && 0 < remaining)
      {
         // flush the buffer if its dirty, since we now need to go to disk
         if (true == mDirty)
            flush();

         // make sure we know the current read location in the underlying file
         mBuffPos = mFile->getPosition();