static int jpeg2000_read_main_headers(Jpeg2000DecoderContext *s)
{
    Jpeg2000CodingStyle *codsty = s->codsty;
    Jpeg2000QuantStyle *qntsty  = s->qntsty;
    uint8_t *properties         = s->properties;

    for (;;) {
        int len, ret = 0;
        uint16_t marker;
        int oldpos;

        if (bytestream2_get_bytes_left(&s->g) < 2) {
            av_log(s->avctx, AV_LOG_ERROR, "Missing EOC\n");
            break;
        }

        marker = bytestream2_get_be16u(&s->g);
        oldpos = bytestream2_tell(&s->g);

        if (marker == JPEG2000_EOC)
            break;

        if (bytestream2_get_bytes_left(&s->g) < 2)
            return AVERROR(EINVAL);
        len = bytestream2_get_be16u(&s->g);
        switch (marker) {
        case JPEG2000_SIZ:
            ret = get_siz(s);
            break;
        case JPEG2000_COC:
            ret = get_coc(s, codsty, properties);
            break;
        case JPEG2000_COD:
            ret = get_cod(s, codsty, properties);
            break;
        case JPEG2000_QCC:
            ret = get_qcc(s, len, qntsty, properties);
            break;
        case JPEG2000_QCD:
            ret = get_qcd(s, len, qntsty, properties);
            break;
        case JPEG2000_SOT:
            ret = get_sot(s, len);
            break;
        case JPEG2000_COM:
            // the comment is ignored
            bytestream2_skip(&s->g, len - 2);
            break;
        case JPEG2000_TLM:
            // Tile-part lengths
            ret = get_tlm(s, len);
            break;
        default:
            av_log(s->avctx, AV_LOG_ERROR,
                   "unsupported marker 0x%.4X at pos 0x%tX\n",
                   marker, bytestream2_tell(&s->g) - 4);
            bytestream2_skip(&s->g, len - 2);
            break;
        }
        if (((bytestream2_tell(&s->g) - oldpos != len) && (marker != JPEG2000_SOT)) || ret) {
            av_log(s->avctx, AV_LOG_ERROR,
                   "error during processing marker segment %.4x\n", marker);
            return ret ? ret : -1;
        }
    }
    return 0;
}