static int s_verify_prelude_state()

in source/event_stream.c [1211:1273]

• 52 lines of code
• 5 McCabe index (conditional complexity)

static int s_verify_prelude_state(
    struct aws_event_stream_streaming_decoder *decoder,
    const uint8_t *data,
    size_t len,
    size_t *processed) /* NOLINT */ {
    (void)data;
    (void)len;
    (void)processed;

    decoder->prelude.headers_len = aws_read_u32(decoder->working_buffer + HEADER_LEN_OFFSET);
    decoder->prelude.prelude_crc = aws_read_u32(decoder->working_buffer + PRELUDE_CRC_OFFSET);
    decoder->prelude.total_len = aws_read_u32(decoder->working_buffer + TOTAL_LEN_OFFSET);

    decoder->running_crc = aws_checksums_crc32(decoder->working_buffer, PRELUDE_CRC_OFFSET, 0);

    if (AWS_LIKELY(decoder->running_crc == decoder->prelude.prelude_crc)) {

        if (AWS_UNLIKELY(
                decoder->prelude.headers_len > AWS_EVENT_STREAM_MAX_HEADERS_SIZE ||
                decoder->prelude.total_len > AWS_EVENT_STREAM_MAX_MESSAGE_SIZE)) {
            aws_raise_error(AWS_ERROR_EVENT_STREAM_MESSAGE_FIELD_SIZE_EXCEEDED);
            char error_message[] = "Maximum message field size exceeded";

            decoder->on_error(
                decoder,
                &decoder->prelude,
                AWS_ERROR_EVENT_STREAM_MESSAGE_FIELD_SIZE_EXCEEDED,
                error_message,
                decoder->user_context);
            return AWS_OP_ERR;
        }

        /* Should only call on_prelude() after passing crc check and limitation check, otherwise call on_prelude() with
         * incorrect prelude is error prune. */
        decoder->on_prelude(decoder, &decoder->prelude, decoder->user_context);

        decoder->running_crc = aws_checksums_crc32(
            decoder->working_buffer + PRELUDE_CRC_OFFSET,
            (int)sizeof(decoder->prelude.prelude_crc),
            decoder->running_crc);
        memset(decoder->working_buffer, 0, sizeof(decoder->working_buffer));
        decoder->state = decoder->prelude.headers_len > 0 ? s_headers_state : s_payload_state;
    } else {
        char error_message[70];
        snprintf(
            error_message,
            sizeof(error_message),
            "CRC Mismatch. prelude_crc was 0x08%" PRIX32 ", but computed 0x08%" PRIX32,
            decoder->prelude.prelude_crc,
            decoder->running_crc);

        aws_raise_error(AWS_ERROR_EVENT_STREAM_PRELUDE_CHECKSUM_FAILURE);
        decoder->on_error(
            decoder,
            &decoder->prelude,
            AWS_ERROR_EVENT_STREAM_PRELUDE_CHECKSUM_FAILURE,
            error_message,
            decoder->user_context);
        return AWS_OP_ERR;
    }

    return AWS_OP_SUCCESS;
}