Method ReadAt

cpp/src/arrow/io/hdfs.cc:138–163

  bool closed() const { return !is_open_; }

  Result<int64_t> ReadAt(int64_t position, int64_t nbytes, uint8_t* buffer) {
    RETURN_NOT_OK(CheckClosed());
    if (!driver_->HasPread()) {
      std::lock_guard<std::mutex> guard(lock_);
      RETURN_NOT_OK(Seek(position));
      return Read(nbytes, buffer);
    }

    constexpr int64_t kMaxBlockSize = std::numeric_limits<int32_t>::max();
    int64_t total_bytes = 0;
    while (nbytes > 0) {
      const auto block_size = static_cast<tSize>(std::min(kMaxBlockSize, nbytes));
      tSize ret =
          driver_->Pread(fs_, file_, static_cast<tOffset>(position), buffer, block_size);
      CHECK_FAILURE(ret, "read");
      DCHECK_LE(ret, block_size);
      if (ret == 0) {
        break;  // EOF
      }
      buffer += ret;
      total_bytes += ret;
      position += ret;
      nbytes -= ret;
    }
    return total_bytes;
  }

  Result<std::shared_ptr<Buffer>> ReadAt(int64_t position, int64_t nbytes) {
    RETURN_NOT_OK(CheckClosed());