Function ReadAt

cpp/src/arrow/ipc/reader_internal.h:58–60

  Result<int64_t> GetSize() override;

  Result<int64_t> ReadAt(int64_t position, int64_t nbytes, void* out) override {
    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) override;