🚀 go-pugleaf

"TMBTC" <jkofsky@bellsouth.net> wrote in message
news:44b994f9$1@newsgroups.borland.com...

> Can anyone help me understand how to use the
> mmioDescend() / mmioAscend() API functions for
> a read operation.

What exactly is unclear about them that you want to know?

> I have a test.wav file that contains the CART chunk. When I read
> it all is fine. When I read a WAVE file that does not contain it, I
> also can't find the 'data' chunk.

That is because you are not seeking the file properly when the chunk is
missing.  In fact, you should not be seeking the file at all.

Try this code instead:

    void __fastcall TForm1::OpenButtonClick(TObject *Sender)
    {
        MMCKINFO mmckInfoWave = {0};
        HMMIO mmioFileHandle = NULL;
        WAVEFORMATEX WaveFormat = {0};
        MMCKINFO mmckInfoSubChunk = {0};
        MMRESULT mmResult = 0;
        CartChunkTagURL cartTag = {0};
        AnsiString asTemp = "";

        Memo1->Lines->Clear();

        mmioFileHandle = mmioOpen(".\\test.wav", NULL, MMIO_READ);
        if( !mmioFileHandle )
        {
            Memo1->Lines->Add("Unable to open file");
            return;
        }

        mmckInfoWave.fccType = mmioFOURCC('W','A','V','E');
        if( mmioDescend(mmioFileHandle, &mmckInfoWave, NULL, MMIO_FINDRIFF)
!= MMSYSERR_NOERROR )
        {
            Memo1->Lines->Add("Error finding WAVE chunk");
            mmioClose(mmioFileHandle, 0);
            return;
        }

        mmckInfoSubChunk.ckid = mmioFOURCC('f','m','t',' ');
        if( mmioDescend(mmioFileHandle, &mmckInfoSubChunk, &mmckInfoWave,
MMIO_FINDCHUNK) != MMSYSERR_NOERROR )
        {
            Memo1->Lines->Add("Error finding FMT chunk");
            mmioClose(mmioFileHandle, 0);
            return;
        }

        if( mmioRead(mmioFileHandle, (HPSTR)&WaveFormat,
mmckInfoSubChunk.cksize) < mmckInfoSubChunk.cksize )
        {
            Memo1->Lines->Add("Error reading FMT chunk");
            mmioClose(mmioFileHandle, 0);
            return;
        }

        asTemp.sprintf("Number of Channels: %d", WaveFormat.nChannels);
        Memo1->Lines->Add(asTemp);
        asTemp.sprintf("Sample Per Second: %d", WaveFormat.nSamplesPerSec);
        Memo1->Lines->Add(asTemp);
        asTemp.sprintf("Avg. Bytes Per Second: %d",
WaveFormat.nAvgBytesPerSec);
        Memo1->Lines->Add(asTemp);
        asTemp.sprintf("Block Alignment: %d", WaveFormat.nBlockAlign);
        Memo1->Lines->Add(asTemp);

        if( mmioAscend(mmioFileHandle, &mmckInfoSubChunk, 0) !=
MMSYSERR_NOERROR )
        {
            Memo1->Lines->Add("Error ascending from FMT chunk");
            mmioClose(mmioFileHandle, 0);
            return;
        }

        mmckInfoSubChunk.ckid = mmioFOURCC('C','A','R','T');
        mmResult = mmioDescend(mmioFileHandle, &mmckInfoSubChunk,
&mmckInfoWave, MMIO_FINDCHUNK);
        if( mmResult != MMSYSERR_NOERROR )
        {
            if( mmResult != MMIOERR_CHUNKNOTFOUND )
            {
                Memo1->Lines->Add("Error finding CART chunk");
                mmioClose(mmioFileHandle, 0);
                return;
            }

            Memo1->Lines->Add("No CART chunk was found");
        }
        else
        {
            if( mmioRead(mmioFileHandle, (HPSTR)&cartTag,
mmckInfoSubChunk.cksize) < mmckInfoSubChunk.cksize )
            {
                Memo1->Lines->Add("Error reading CART chunk");
                mmioClose(mmioFileHandle, 0);
                return;
            }

            asTemp.sprintf("Size of CART: %d", mmckInfoSubChunk.cksize);
            Memo1->Lines->Add(asTemp);

            mmioAscend(mmioFileHandle, &mmckInfoSubChunk, 0);
        }

        ZeroMemory(&mmckInfoSubChunk, sizeof(mmckInfoSubChunk));

        mmckInfoSubChunk.ckid = mmioFOURCC('d','a','t','a');
        mmResult = mmioDescend(mmioFileHandle, &mmckInfoSubChunk,
&mmckInfoWave, MMIO_FINDCHUNK);
        if( mmResult != MMSYSERR_NOERROR )
        {
            if( mmResult != MMIOERR_CHUNKNOTFOUND )
                Memo1->Lines->Add("Error finding DATA chunk");
            else
                Memo1->Lines->Add("No DATA chunk was found.");
        }
        else
        {
            asTemp.sprintf("Size of Data: %d", mmckInfoSubChunk.cksize);
            Memo1->Lines->Add(asTemp);
        }

        mmioClose(mmioFileHandle, 0);
    }


Gambit