ParseStatus caretParseHeader()

in mcrouter/lib/network/CaretProtocol.cpp [110:197]
72 lines of code
16 McCabe index (conditional complexity)

ParseStatus caretParseHeader(
    const uint8_t* buff,
    size_t nbuf,
    CaretMessageInfo& headerInfo) {
  /* we need the magic byte and the first byte of encoded header
     to determine if we have enough data in the buffer to get the
     entire header */
  if (nbuf < 2) {
    return ParseStatus::NotEnoughData;
  }

  if (buff[0] != kCaretMagicByte) {
    return ParseStatus::MessageParseError;
  }

  const char* buf = reinterpret_cast<const char*>(buff);
  size_t encodedLength = folly::GroupVarint32::encodedSize(buf + 1);

  if (nbuf < encodedLength + 1) {
    return ParseStatus::NotEnoughData;
  }

  uint32_t additionalFields;
  folly::GroupVarint32::decode_simple(
      buf + 1,
      &headerInfo.bodySize,
      &headerInfo.typeId,
      &headerInfo.reqId,
      &additionalFields);

  folly::StringPiece range(buf, nbuf);
  range.advance(encodedLength + 1);

  // Additional fields are sequence of (key,value) pairs
  resetAdditionalFields(headerInfo);
  for (uint32_t i = 0; i < additionalFields; i++) {
    size_t fieldType;
    if (auto maybeFieldType = folly::tryDecodeVarint(range)) {
      fieldType = *maybeFieldType;
    } else {
      return ParseStatus::NotEnoughData;
    }

    size_t fieldValue;
    if (auto maybeFieldValue = folly::tryDecodeVarint(range)) {
      fieldValue = *maybeFieldValue;
    } else {
      return ParseStatus::NotEnoughData;
    }

    if (fieldType >
        static_cast<uint64_t>(CaretAdditionalFieldType::SERVER_LOAD)) {
      // Additional Field Type not recognized, ignore.
      continue;
    }

    switch (static_cast<CaretAdditionalFieldType>(fieldType)) {
      case CaretAdditionalFieldType::TRACE_ID:
        headerInfo.traceId.first = fieldValue;
        break;
      case CaretAdditionalFieldType::TRACE_NODE_ID:
        headerInfo.traceId.second = fieldValue;
        break;
      case CaretAdditionalFieldType::SUPPORTED_CODECS_FIRST_ID:
        headerInfo.supportedCodecsFirstId = fieldValue;
        break;
      case CaretAdditionalFieldType::SUPPORTED_CODECS_SIZE:
        headerInfo.supportedCodecsSize = fieldValue;
        break;
      case CaretAdditionalFieldType::USED_CODEC_ID:
        headerInfo.usedCodecId = fieldValue;
        break;
      case CaretAdditionalFieldType::UNCOMPRESSED_BODY_SIZE:
        headerInfo.uncompressedBodySize = fieldValue;
        break;
      case CaretAdditionalFieldType::DROP_PROBABILITY:
        headerInfo.dropProbability = fieldValue;
        break;
      case CaretAdditionalFieldType::SERVER_LOAD:
        headerInfo.serverLoad = ServerLoad(fieldValue);
        break;
    }
  }

  headerInfo.headerSize = range.cbegin() - buf;

  return ParseStatus::Ok;
}