std::string S3FileManager::readBytes()

in fbpcf/io/S3FileManager.cpp [37:64]

• 21 lines of code
• 2 McCabe index (conditional complexity)

std::string S3FileManager::readBytes(
    const std::string& fileName,
    std::size_t start,
    std::size_t end) {
  const auto& ref = fbpcf::aws::uriToObjectReference(fileName);
  Aws::S3::Model::GetObjectRequest request;
  std::stringstream ss;
  // NOTE: The AWS API uses a closed interval [a, b] to request a range while
  // C++ string (and most "normal" programming APIs) use a half-open interval
  // [a, b). Therefore, we subtract one here to make this usage consistent with
  // other APIs. If the user passes in readBytes(path, 0, 4), we would expect
  // to generate the range "bytes=0-3"
  ss << "bytes=" << start << '-' << (end - 1);
  request.SetBucket(ref.bucket);
  request.SetKey(ref.key);
  request.SetRange(ss.str());

  auto outcome = s3Client_->GetObject(request);
  if (!outcome.IsSuccess()) {
    throw AwsException{outcome.GetError().GetMessage()};
  }

  auto stream =
      std::make_unique<S3InputStream>(outcome.GetResultWithOwnership());
  std::stringstream ss2;
  ss2 << stream->get().rdbuf();
  return ss2.str();
}