std::string LocalFileManager::readBytes()

in fbpcf/io/LocalFileManager.cpp [54:91]

• 30 lines of code
• 4 McCabe index (conditional complexity)

std::string LocalFileManager::readBytes(
    const std::string& fileName,
    std::size_t start,
    std::size_t end) {
  if (start > end) {
    throw PcfException{folly::sformat(
        "Start byte: <{}> is larger than the end: <{}>", start, end)};
  }
  auto stream = getInputStream(fileName);
  std::istream& is = stream->get();

  // get length of file
  is.seekg(0, std::ios::end);
  size_t length = is.tellg();
  if (start > length) {
    throw PcfException{folly::sformat(
        "Start byte: <{}> is larger than the length: <{}>", start, length)};
  }
  is.seekg(start, std::ios::beg);

  auto validatedEnd = std::min(length, end);
  size_t bufferLength = validatedEnd - start;

  char buffer[bufferLength + 1];

  // read data as a block:
  if (is.readsome(buffer, bufferLength) != bufferLength) {
    throw PcfException{
        folly::sformat(
            "Hit exception when trying to read bytes from {}", fileName),
    };
  }

  buffer[bufferLength] = '\0';

  std::string s{buffer};
  return s;
}