function concatBulkBuffer (parser) {
  const list = parser.bufferCache;
  const oldOffset = parser.offset;
  const length = parser.bigStrSize - oldOffset - 2;
  var chunks = list.length;
  var offset = parser.bigStrSize - parser.totalChunkSize;
  parser.offset = offset;
  if (offset <= 2) {
    if (chunks === 2) {
      return list[0].slice(oldOffset, list[0].length + offset - 2)
    }
    chunks--;
    offset = list[list.length - 2].length + offset;
  }
  resizeBuffer(length);
  const start = bufferOffset;
  list[0].copy(bufferPool, start, oldOffset, list[0].length);
  bufferOffset += list[0].length - oldOffset;
  for (var i = 1; i < chunks - 1; i++) {
    list[i].copy(bufferPool, bufferOffset);
    bufferOffset += list[i].length;
  }
  list[i].copy(bufferPool, bufferOffset, 0, offset - 2);
  bufferOffset += offset - 2;
  return bufferPool.slice(start, bufferOffset)
}
Concat the collected chunks from parser.bufferCache.

Increases the bufferPool size beforehand if necessary.

@param {JavascriptRedisParser} parser
@returns {Buffer}