static int xwd_decode_frame(AVCodecContext *avctx, void *data,

                            int *got_frame, AVPacket *avpkt)

{

    AVFrame *p = data;

    const uint8_t *buf = avpkt->data;

    int i, ret, buf_size = avpkt->size;

    uint32_t version, header_size, vclass, ncolors;

    uint32_t xoffset, be, bpp, lsize, rsize;

    uint32_t pixformat, pixdepth, bunit, bitorder, bpad;

    uint32_t rgb[3];

    uint8_t *ptr;

    GetByteContext gb;



    if (buf_size < XWD_HEADER_SIZE)

        return AVERROR_INVALIDDATA;



    bytestream2_init(&gb, buf, buf_size);

    header_size = bytestream2_get_be32u(&gb);



    version = bytestream2_get_be32u(&gb);

    if (version != XWD_VERSION) {

        av_log(avctx, AV_LOG_ERROR, "unsupported version\n");

        return AVERROR_INVALIDDATA;

    }



    if (buf_size < header_size || header_size < XWD_HEADER_SIZE) {

        av_log(avctx, AV_LOG_ERROR, "invalid header size\n");

        return AVERROR_INVALIDDATA;

    }



    pixformat     = bytestream2_get_be32u(&gb);

    pixdepth      = bytestream2_get_be32u(&gb);

    avctx->width  = bytestream2_get_be32u(&gb);

    avctx->height = bytestream2_get_be32u(&gb);

    xoffset       = bytestream2_get_be32u(&gb);

    be            = bytestream2_get_be32u(&gb);

    bunit         = bytestream2_get_be32u(&gb);

    bitorder      = bytestream2_get_be32u(&gb);

    bpad          = bytestream2_get_be32u(&gb);

    bpp           = bytestream2_get_be32u(&gb);

    lsize         = bytestream2_get_be32u(&gb);

    vclass        = bytestream2_get_be32u(&gb);

    rgb[0]        = bytestream2_get_be32u(&gb);

    rgb[1]        = bytestream2_get_be32u(&gb);

    rgb[2]        = bytestream2_get_be32u(&gb);

    bytestream2_skipu(&gb, 8);

    ncolors       = bytestream2_get_be32u(&gb);

    bytestream2_skipu(&gb, header_size - (XWD_HEADER_SIZE - 20));



    av_log(avctx, AV_LOG_DEBUG,

           "pixformat %"PRIu32", pixdepth %"PRIu32", bunit %"PRIu32", bitorder %"PRIu32", bpad %"PRIu32"\n",

           pixformat, pixdepth, bunit, bitorder, bpad);

    av_log(avctx, AV_LOG_DEBUG,

           "vclass %"PRIu32", ncolors %"PRIu32", bpp %"PRIu32", be %"PRIu32", lsize %"PRIu32", xoffset %"PRIu32"\n",

           vclass, ncolors, bpp, be, lsize, xoffset);

    av_log(avctx, AV_LOG_DEBUG,

           "red %0"PRIx32", green %0"PRIx32", blue %0"PRIx32"\n",

           rgb[0], rgb[1], rgb[2]);



    if (pixformat > XWD_Z_PIXMAP) {

        av_log(avctx, AV_LOG_ERROR, "invalid pixmap format\n");

        return AVERROR_INVALIDDATA;

    }



    if (pixdepth == 0 || pixdepth > 32) {

        av_log(avctx, AV_LOG_ERROR, "invalid pixmap depth\n");

        return AVERROR_INVALIDDATA;

    }



    if (xoffset) {

        avpriv_request_sample(avctx, "xoffset %"PRIu32"", xoffset);

        return AVERROR_PATCHWELCOME;

    }



    if (be > 1) {

        av_log(avctx, AV_LOG_ERROR, "invalid byte order\n");

        return AVERROR_INVALIDDATA;

    }



    if (bitorder > 1) {

        av_log(avctx, AV_LOG_ERROR, "invalid bitmap bit order\n");

        return AVERROR_INVALIDDATA;

    }



    if (bunit != 8 && bunit != 16 && bunit != 32) {

        av_log(avctx, AV_LOG_ERROR, "invalid bitmap unit\n");

        return AVERROR_INVALIDDATA;

    }



    if (bpad != 8 && bpad != 16 && bpad != 32) {

        av_log(avctx, AV_LOG_ERROR, "invalid bitmap scan-line pad\n");

        return AVERROR_INVALIDDATA;

    }



    if (bpp == 0 || bpp > 32) {

        av_log(avctx, AV_LOG_ERROR, "invalid bits per pixel\n");

        return AVERROR_INVALIDDATA;

    }



    if (ncolors > 256) {

        av_log(avctx, AV_LOG_ERROR, "invalid number of entries in colormap\n");

        return AVERROR_INVALIDDATA;

    }



    if ((ret = av_image_check_size(avctx->width, avctx->height, 0, NULL)) < 0)

        return ret;



    rsize = FFALIGN(avctx->width * bpp, bpad) / 8;

    if (lsize < rsize) {

        av_log(avctx, AV_LOG_ERROR, "invalid bytes per scan-line\n");

        return AVERROR_INVALIDDATA;

    }



    if (bytestream2_get_bytes_left(&gb) < ncolors * XWD_CMAP_SIZE + (uint64_t)avctx->height * lsize) {

        av_log(avctx, AV_LOG_ERROR, "input buffer too small\n");

        return AVERROR_INVALIDDATA;

    }



    if (pixformat != XWD_Z_PIXMAP) {

        avpriv_report_missing_feature(avctx, "Pixmap format %"PRIu32, pixformat);

        return AVERROR_PATCHWELCOME;

    }



    avctx->pix_fmt = AV_PIX_FMT_NONE;

    switch (vclass) {

    case XWD_STATIC_GRAY:

    case XWD_GRAY_SCALE:

        if (bpp != 1 && bpp != 8)

            return AVERROR_INVALIDDATA;

        if (pixdepth == 1) {

            avctx->pix_fmt = AV_PIX_FMT_MONOWHITE;

        } else if (pixdepth == 8) {

            avctx->pix_fmt = AV_PIX_FMT_GRAY8;

        }

        break;

    case XWD_STATIC_COLOR:

    case XWD_PSEUDO_COLOR:

        if (bpp == 8)

            avctx->pix_fmt = AV_PIX_FMT_PAL8;

        break;

    case XWD_TRUE_COLOR:

    case XWD_DIRECT_COLOR:

        if (bpp != 16 && bpp != 24 && bpp != 32)

            return AVERROR_INVALIDDATA;

        if (bpp == 16 && pixdepth == 15) {

            if (rgb[0] == 0x7C00 && rgb[1] == 0x3E0 && rgb[2] == 0x1F)

                avctx->pix_fmt = be ? AV_PIX_FMT_RGB555BE : AV_PIX_FMT_RGB555LE;

            else if (rgb[0] == 0x1F && rgb[1] == 0x3E0 && rgb[2] == 0x7C00)

                avctx->pix_fmt = be ? AV_PIX_FMT_BGR555BE : AV_PIX_FMT_BGR555LE;

        } else if (bpp == 16 && pixdepth == 16) {

            if (rgb[0] == 0xF800 && rgb[1] == 0x7E0 && rgb[2] == 0x1F)

                avctx->pix_fmt = be ? AV_PIX_FMT_RGB565BE : AV_PIX_FMT_RGB565LE;

            else if (rgb[0] == 0x1F && rgb[1] == 0x7E0 && rgb[2] == 0xF800)

                avctx->pix_fmt = be ? AV_PIX_FMT_BGR565BE : AV_PIX_FMT_BGR565LE;

        } else if (bpp == 24) {

            if (rgb[0] == 0xFF0000 && rgb[1] == 0xFF00 && rgb[2] == 0xFF)

                avctx->pix_fmt = be ? AV_PIX_FMT_RGB24 : AV_PIX_FMT_BGR24;

            else if (rgb[0] == 0xFF && rgb[1] == 0xFF00 && rgb[2] == 0xFF0000)

                avctx->pix_fmt = be ? AV_PIX_FMT_BGR24 : AV_PIX_FMT_RGB24;

        } else if (bpp == 32) {

            if (rgb[0] == 0xFF0000 && rgb[1] == 0xFF00 && rgb[2] == 0xFF)

                avctx->pix_fmt = be ? AV_PIX_FMT_ARGB : AV_PIX_FMT_BGRA;

            else if (rgb[0] == 0xFF && rgb[1] == 0xFF00 && rgb[2] == 0xFF0000)

                avctx->pix_fmt = be ? AV_PIX_FMT_ABGR : AV_PIX_FMT_RGBA;

        }

        bytestream2_skipu(&gb, ncolors * XWD_CMAP_SIZE);

        break;

    default:

        av_log(avctx, AV_LOG_ERROR, "invalid visual class\n");

        return AVERROR_INVALIDDATA;

    }



    if (avctx->pix_fmt == AV_PIX_FMT_NONE) {

        avpriv_request_sample(avctx,

                              "Unknown file: bpp %"PRIu32", pixdepth %"PRIu32", vclass %"PRIu32"",

                              bpp, pixdepth, vclass);

        return AVERROR_PATCHWELCOME;

    }



    if ((ret = ff_get_buffer(avctx, p, 0)) < 0)

        return ret;



    p->key_frame = 1;

    p->pict_type = AV_PICTURE_TYPE_I;



    if (avctx->pix_fmt == AV_PIX_FMT_PAL8) {

        uint32_t *dst = (uint32_t *)p->data[1];

        uint8_t red, green, blue;



        for (i = 0; i < ncolors; i++) {



            bytestream2_skipu(&gb, 4); // skip colormap entry number

            red    = bytestream2_get_byteu(&gb);

            bytestream2_skipu(&gb, 1);

            green  = bytestream2_get_byteu(&gb);

            bytestream2_skipu(&gb, 1);

            blue   = bytestream2_get_byteu(&gb);

            bytestream2_skipu(&gb, 3); // skip bitmask flag and padding



            dst[i] = red << 16 | green << 8 | blue;

        }

    }



    ptr = p->data[0];

    for (i = 0; i < avctx->height; i++) {

        bytestream2_get_bufferu(&gb, ptr, rsize);

        bytestream2_skipu(&gb, lsize - rsize);

        ptr += p->linesize[0];

    }



    *got_frame       = 1;



    return buf_size;

}
