Function Validate

include/bmpread/bmpread.c:535–609

Reads and validates the bitmap header metadata from the context's file * object. Assumes the file pointer is at the start of the file. Returns 1 if * ok or 0 if error or invalid file. */

 * ok or 0 if error or invalid file.
 */
static int Validate(read_context * p_ctx)
{
    if(!ReadHeader(&p_ctx->header, p_ctx->fp)) return 0;
    if(!ReadInfo(  &p_ctx->info,   p_ctx->fp)) return 0;

    if(p_ctx->info.info_size > UINT32_MAX - BMP_HEADER_SIZE) return 0;
    p_ctx->headers_size = BMP_HEADER_SIZE + p_ctx->info.info_size;

    if(p_ctx->header.data_offset < p_ctx->headers_size) return 0;
    p_ctx->after_headers = p_ctx->header.data_offset - p_ctx->headers_size;

    if(p_ctx->info.width <= 0 || p_ctx->info.height == 0) return 0;

    if(!CanMakeSizeT(p_ctx->info.width))  return 0;
    if(!CanNegate(   p_ctx->info.height)) return 0;
    p_ctx->lines = ((p_ctx->info.height < 0) ?
                    -p_ctx->info.height :
                     p_ctx->info.height);

    if(!(p_ctx->flags & BMPREAD_ANY_SIZE))
    {
        /* Both of these values have just been checked against being negative,
         * and thus it's safe to pass them on as uint32_t.
         */
        if(!IsPowerOf2(p_ctx->info.width)) return 0;
        if(!IsPowerOf2(p_ctx->lines))      return 0;
    }

    switch(p_ctx->info.compression)
    {
        case COMPRESSION_NONE:
            if(p_ctx->info.bits != 1 && p_ctx->info.bits != 4 &&
               p_ctx->info.bits != 8 && p_ctx->info.bits != 24) return 0;
            break;

        case COMPRESSION_BITFIELDS:
            if(p_ctx->info.bits != 16 && p_ctx->info.bits != 32) return 0;
            break;

        default: /* No compression supported yet (TODO: handle RLE). */
            return 0;
    }

    p_ctx->file_line_len = GetLineLength(p_ctx->info.width, p_ctx->info.bits);
    if(p_ctx->file_line_len == 0) return 0;

    p_ctx->out_channels = ((p_ctx->flags & BMPREAD_ALPHA) ? 4 : 3);

    /* This check happens outside the following if, where it would seem to
     * belong, because we make the same computation again in the future.
     */
    if(!CanMultiply(p_ctx->info.width, p_ctx->out_channels)) return 0;

    if(p_ctx->flags & BMPREAD_BYTE_ALIGN)
        p_ctx->out_line_len = (size_t)p_ctx->info.width * p_ctx->out_channels;
    else
    {
        p_ctx->out_line_len = GetLineLength(p_ctx->info.width,