Function protocol

test/tools/mongodb-mock/src/server.js:250–315

(self, message)

}

const protocol = function (self, message) {
  let index = 0;
  self.isCompressed = false;
  // Get the size for the message
  const size =
    message[index++] |
    (message[index++] << 8) |
    (message[index++] << 16) |
    (message[index++] << 24);
  if (size !== message.length) throw new Error('corrupt wire protocol message');
  // Adjust to opcode
  index = 12;
  // Get the opCode for the message
  let type =
    message[index++] |
    (message[index++] << 8) |
    (message[index++] << 16) |
    (message[index++] << 24);

  // Unpack and decompress if the message is OP_COMPRESSED
  if (type === opcodes.OP_COMPRESSED) {
    const requestID = message.readInt32LE(4);
    const responseTo = message.readInt32LE(8);
    const originalOpcode = message.readInt32LE(16);
    const uncompressedSize = message.readInt32LE(20);
    const compressorID = message.readUInt8(24);

    const compressedData = message.slice(25);
    let uncompressedData;
    switch (compressorID) {
      case compressorIDs.snappy:
        uncompressedData = snappy.uncompressSync(compressedData);
        break;
      case compressorIDs.zlib:
        uncompressedData = zlib.inflateSync(compressedData);
        break;
      default:
        uncompressedData = compressedData;
    }

    if (uncompressedData.length !== uncompressedSize) {
      throw new Error(
        'corrupt wire protocol message: uncompressed message is not the correct size'
      );
    }

    // Reconstruct the msgHeader of the uncompressed opcode
    const newMsgHeader = Buffer(MESSAGE_HEADER_SIZE);
    newMsgHeader.writeInt32LE(MESSAGE_HEADER_SIZE + uncompressedData.length, 0);
    newMsgHeader.writeInt32LE(requestID, 4);
    newMsgHeader.writeInt32LE(responseTo, 8);
    newMsgHeader.writeInt32LE(originalOpcode, 12);

    // Full uncompressed message
    message = Buffer.concat([newMsgHeader, uncompressedData]);
    type = originalOpcode;

    // Compressed flag