Method ReadAt

cpp/src/arrow/io/concurrency.h:210–212

  // to use the exclusive_guard.

  Result<int64_t> ReadAt(int64_t position, int64_t nbytes, void* out) final {
    return ReadAt(position, nbytes, /*allow_short_read=*/true, out);
  }

  Result<int64_t> ReadAt(int64_t position, int64_t nbytes, bool allow_short_read,
                         void* out) final {