Function ReadInfo

include/bmpread/bmpread.c:275–312

Reads bitmap metadata from fp into info. Returns 0 on EOF or invalid info, * or nonzero on success. info is assumed to be initialized to 0 already. */

 * or nonzero on success.  info is assumed to be initialized to 0 already.
 */
static int ReadInfo(bmp_info * info, FILE * fp)
{
    if(!ReadLittleUint32(&info->info_size, fp)) return 0;

    /* Older formats might not have all the fields we require, so this check
     * comes first.
     */
    if(info->info_size < MIN_INFO_SIZE) return 0;

    if(!ReadLittleInt32( &info->width,       fp)) return 0;
    if(!ReadLittleInt32( &info->height,      fp)) return 0;
    if(!ReadLittleUint16(&info->planes,      fp)) return 0;
    if(!ReadLittleUint16(&info->bits,        fp)) return 0;
    if(!ReadLittleUint32(&info->compression, fp)) return 0;
    if(!ReadLittleUint32(&info->unused0[0],  fp)) return 0;
    if(!ReadLittleUint32(&info->unused0[1],  fp)) return 0;
    if(!ReadLittleUint32(&info->unused0[2],  fp)) return 0;
    if(!ReadLittleUint32(&info->colors,      fp)) return 0;
    if(!ReadLittleUint32(&info->unused1,     fp)) return 0;

    /* We don't bother to even try to read bitmasks if they aren't needed,
     * since they won't be present in Windows 3 format bitmap files.
     */
    if(info->compression == COMPRESSION_BITFIELDS)
    {
        /* Reject Windows NT format files with bitfields, since we don't
         * support them, and their masks aren't part of the info header anyway.
         */
        if(info->info_size == BMP3_INFO_SIZE) return 0;

        if(!ReadLittleUint32(&info->masks[0], fp)) return 0;
        if(!ReadLittleUint32(&info->masks[1], fp)) return 0;
        if(!ReadLittleUint32(&info->masks[2], fp)) return 0;
        if(!ReadLittleUint32(&info->masks[3], fp)) return 0;
    }

    return 1;
}

/* Bitfields for 16- and 32-bit files.  We track the first set bit (rightmost
 * being 0) and how many bits it spans.