Lecture à partir d’un flux et écriture dans un autre

L’exemple suivant lit les données d’un flux, effectue une opération avec les données et écrit les données compressées dans un flux d’un nouveau fichier.

// SaveSmall - copies a stream of data from one file, compresses 
// the stream, and writes the compressed stream to a new file. 
// 
// ps stream interface pointer 
// lpFilename - new AVI file to build 
// 
 
void SaveSmall(PAVISTREAM ps, LPSTR lpFilename) 
{ 
    PAVIFILE         pf; 
    PAVISTREAM       psSmall; 
    HRESULT          hr; 
    AVISTREAMINFO    strhdr; 
    BITMAPINFOHEADER bi; 
    BITMAPINFOHEADER biNew; 
    LONG             lStreamSize; 
    LPVOID           lpOld; 
    LPVOID           lpNew; 
 
    // Determine the size of the format data using 
    // AVIStreamFormatSize. 
    AVIStreamFormatSize(ps, 0, &lStreamSize); 
    if (lStreamSize > sizeof(bi)) // Format too large? 
        return; 
 
    lStreamSize = sizeof(bi); 
    hr = AVIStreamReadFormat(ps, 0, &bi, &lStreamSize); // Read format 
    if (bi.biCompression != BI_RGB) // Wrong compression format? 
        return; 
 
    hr = AVIStreamInfo(ps, &strhdr, sizeof(strhdr)); 
 
    // Create new AVI file using AVIFileOpen. 
    hr = AVIFileOpen(&pf, lpFilename, OF_WRITE | OF_CREATE, NULL); 
    if (hr != 0) 
        return; 
 
    // Set parameters for the new stream. 
    biNew = bi; 
    biNew.biWidth /= 2; 
    biNew.biHeight /= 2; 
    biNew.biSizeImage = ((((UINT)biNew.biBitCount * biNew.biWidth 
                        + 31)&~31) / 8) * biNew.biHeight; 
    SetRect(&strhdr.rcFrame, 0, 0, (int) biNew.biWidth, 
            (int) biNew.biHeight); 
 
    // Create a stream using AVIFileCreateStream. 
    hr = AVIFileCreateStream(pf, &psSmall, &strhdr); 
    if (hr != 0) {            //Stream created OK? If not, close file. 
        AVIFileRelease(pf); 
        return; 
    } 
 
    // Set format of new stream using AVIStreamSetFormat. 
    hr = AVIStreamSetFormat(psSmall, 0, &biNew, sizeof(biNew)); 
    if (hr != 0) { 
        AVIStreamRelease(psSmall); 
        AVIFileRelease(pf); 
        return; 
    } 
 
    // Allocate memory for the bitmaps. 
    lpOld = GlobalAllocPtr(GMEM_MOVEABLE, bi.biSizeImage); 
    lpNew = GlobalAllocPtr(GMEM_MOVEABLE, biNew.biSizeImage); 
 
    // Read the stream data using AVIStreamRead. 
    for (lStreamSize = AVIStreamStart(ps); lStreamSize <
        AVIStreamEnd(ps); lStreamSize++) { 
        hr = AVIStreamRead(ps, lStreamSize, 1, lpOld, bi.biSizeImage,
            NULL, NULL); 
        // 
        // Place error check here. 
        // 
 
        // Do something with the data and write it to lpNew buffer. 
 
        // Save the compressed data using AVIStreamWrite. 
        hr = AVIStreamWrite(psSmall, lStreamSize, 1, lpNew,
            biNew.biSizeImage, AVIIF_KEYFRAME, NULL, NULL); 
    } 
 
     // Close the stream and file. 
    AVIStreamRelease(psSmall); 
    AVIFileRelease(pf); 
}