Performing File I/O on RIFF Files

The following example shows how to open a RIFF file for buffered I/O, as well as how to descend, ascend, and read  RIFF  chunks.

// ReversePlay--Plays a waveform-audio file backward.

void ReversePlay()

{ 

    char        szFileName[128];    // filename of file to open

    HMMIO       hmmio;              // file handle for open file

    MMCKINFO    mmckinfoParent;     // parent chunk information

    MMCKINFO    mmckinfoSubchunk;   // subchunk information structure

    DWORD       dwFmtSize;          // size of "FMT" chunk

    DWORD       dwDataSize;         // size of "DATA" chunk

    WAVEFORMAT  *pFormat;           // address of "FMT" chunk

    HPSTR       lpData;             // address of "DATA" chunk

    // Get the filename from the edit control.

    .

    .

    .

    // Open the file for reading with buffered I/O

    // by using the default internal buffer

    if(!(hmmio = mmioOpen(szFileName, NULL,

        MMIO_READ | MMIO_ALLOCBUF)))

    { 

        Error("Failed to open file.");

        return;

    }

    // Locate a "RIFF" chunk with a "WAVE" form type to make

    // sure the file is a waveform-audio file.

    mmckinfoParent.fccType = mmioFOURCC('W', 'A', 'V', 'E');

    if (mmioDescend(hmmio, (LPMMCKINFO) &mmckinfoParent, NULL,

        MMIO_FINDRIFF))

    { 

        Error("This is not a waveform-audio file.");

        mmioClose(hmmio, 0);

        return;

    }

    // Find the "FMT" chunk (form type "FMT"); it must be

    // a subchunk of the "RIFF" chunk.

    mmckinfoSubchunk.ckid = mmioFOURCC('f', 'm', 't', ' ');

    if (mmioDescend(hmmio, &mmckinfoSubchunk, &mmckinfoParent,

        MMIO_FINDCHUNK))

    { 

        Error("Waveform-audio file has no "FMT" chunk.");

        mmioClose(hmmio, 0);

        return;

    }

    // Get the size of the "FMT" chunk. Allocate

    // and lock memory for it.

    dwFmtSize = mmckinfoSubchunk.cksize;

    .

    .

    .

    // Read the "FMT" chunk.

    if (mmioRead(hmmio, (HPSTR) pFormat, dwFmtSize) != dwFmtSize){ 

        Error("Failed to read format chunk.");

        .

        .

        .

        mmioClose(hmmio, 0);

        return;

    }

    // Ascend out of the "FMT" subchunk.

    mmioAscend(hmmio, &mmckinfoSubchunk 0);

    // Find the data subchunk. The current file position should be at

    // the beginning of the data chunk; however, you should not make

    // this assumption. Use mmioDescend to locate the data chunk.

    mmckinfoSubchunk.ckid = mmioFOURCC('d', 'a', 't', 'a');

    if (mmioDescend(hmmio, &mmckinfoSubchunk, &mmckinfoParent,

        MMIO_FINDCHUNK))

    { 

        Error("Waveform-audio file has no data chunk.");

        .

        .

        .

        mmioClose(hmmio, 0);

        return;

    }

    // Get the size of the data subchunk.

    dwDataSize = mmckinfoSubchunk.cksize;

    if (dwDataSize == 0L){ 

        Error("The data chunk contains no data.");

        .

        .

        .

        mmioClose(hmmio, 0);

        return;

    }

    // Open a waveform-audio output device.

    .

    .

    .

    // Allocate and lock memory for the waveform-audio data.

    .

    .

    .

    // Read the waveform-audio data subchunk.

    if(mmioRead(hmmio, (HPSTR) lpData, dwDataSize) != dwDataSize){ 

        Error("Failed to read data chunk.");

        .

        .

        .

        mmioClose(hmmio, 0);

        return;

    }

    // Close the file.

    mmioClose(hmmio, 0);

    // Reverse the sound and play it.

    .

    .

    .

}