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Accessing a File I/O Buffer
The following example accesses an I/O buffer directly to read data from a
waveform-audio file.
HMMIO hmmio;
MMIOINFO mmioinfo;
DWORD dwDataSize;
DWORD dwCount;
HPSTR hptr;
// Get information about the file I/O buffer.
if (mmioGetInfo(hmmio, &mmioinfo, 0))
{
Error("Failed to get I/O buffer info.");
.
.
.
mmioClose(hmmio, 0);
return;
}
// Read the entire file by directly reading the file I/O buffer.
// When the end of the I/O buffer is reached, advance the buffer.
for (dwCount = dwDataSize, hptr = lpData; dwCount 0; dwCount--)
{
// Check to see if the I/O buffer must be advanced.
if (mmioinfo.pchNext == mmioinfo.pchEndRead)
{
if(mmioAdvance(hmmio, &mmioinfo, MMIO_READ))
{
Error("Failed to advance buffer.");
.
.
.
mmioClose(hmmio, 0);
return;
}
}
// Get a character from the buffer.
*hptr++ = *mmioinfo.pchNext++;
}
// End direct buffer access and close the file.
mmioSetInfo(hmmio, &mmioinfo, 0);
mmioClose(hmmio, 0);
When you finish accessing a file I/O buffer, call the mmioSetInfo function, passing an address of the MMIOINFO structure filled by the mmioGetInfo function. If you wrote to the buffer, set the MMIO_DIRTY flag in the dwFlags member of the MMIOINFO structure before calling mmioSetInfo. Otherwise, the buffer will not be flushed to disk.
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