Function DEFINE_SMALL_ARRAY

src/brpc/rtmp.cpp:575–644

the buf should be short generally, copy it out to continuous memory to simplify parsing.

    // the buf should be short generally, copy it out to continuous memory
    // to simplify parsing.
    DEFINE_SMALL_ARRAY(char, cont_buf, buf.size(), 64);
    buf.copy_to(cont_buf, buf.size());
    return Create(cont_buf, buf.size());
}

butil::Status AVCDecoderConfigurationRecord::Create(const void* data, size_t len) {
    butil::StringPiece buf((const char*)data, len);
    if (buf.size() < 6) {
        return butil::Status(EINVAL, "Length=%lu is not long enough",
                            (unsigned long)buf.size());
    }
    // skip configurationVersion at buf[0]
    avc_profile = (AVCProfile)buf[1];
    // skip profile_compatibility at buf[2]
    avc_level = (AVCLevel)buf[3];
    
    // 5.3.4.2.1 Syntax, H.264-AVC-ISO_IEC_14496-15.pdf, page 16
    // 5.2.4.1 AVC decoder configuration record
    // 5.2.4.1.2 Semantics
    // The value of this field shall be one of 0, 1, or 3 corresponding to a
    // length encoded with 1, 2, or 4 bytes, respectively.
    length_size_minus1 = buf[4] & 0x03;
    if (length_size_minus1 == 2) {
        return butil::Status(EINVAL, "lengthSizeMinusOne should never be 2");
    }

    // Parsing SPS
    const int num_sps = (int)(buf[5] & 0x1f);
    buf.remove_prefix(6);
    sps_list.clear();
    sps_list.reserve(num_sps);
    for (int i = 0; i < num_sps; ++i) {
        if (buf.size() < 2) {
            return butil::Status(EINVAL, "Not enough data to decode SPS-length");
        }
        const uint16_t sps_length = policy::ReadBigEndian2Bytes(buf.data());
        if (buf.size() < 2u + sps_length) {
            return butil::Status(EINVAL, "Not enough data to decode SPS");
        }
        if (sps_length > 0) {
            butil::Status st = ParseSPS(buf.data() + 2, sps_length);
            if (!st.ok()) {
                return st;
            }
            sps_list.push_back(buf.substr(2, sps_length).as_string());
        }
        buf.remove_prefix(2 + sps_length);
    }
    // Parsing PPS
    pps_list.clear();
    if (buf.empty()) {
        return butil::Status(EINVAL, "Not enough data to decode PPS");
    }
    const int num_pps = (int)buf[0];
    buf.remove_prefix(1);
    for (int i = 0; i < num_pps; ++i) {
        if (buf.size() < 2) {
            return butil::Status(EINVAL, "Not enough data to decode PPS-length");