Function ReadSchema

cpp/src/arrow/ipc/read_write_test.cc:1335–1391

};

struct StreamWriterHelper {
  static constexpr bool kIsFileFormat = false;

  Status Init(const std::shared_ptr<Schema>& schema, const IpcWriteOptions& options) {
    ARROW_ASSIGN_OR_RAISE(buffer_, AllocateResizableBuffer(0));
    sink_.reset(new io::BufferOutputStream(buffer_));
    ARROW_ASSIGN_OR_RAISE(writer_, MakeStreamWriter(sink_.get(), schema, options));
    return Status::OK();
  }

  Status WriteBatch(const std::shared_ptr<RecordBatch>& batch,
                    const std::shared_ptr<const KeyValueMetadata>& metadata = nullptr) {
    RETURN_NOT_OK(writer_->WriteRecordBatch(*batch, metadata));
    return Status::OK();
  }

  Status WriteTable(const RecordBatchVector& batches) {
    ARROW_ASSIGN_OR_RAISE(auto table, Table::FromRecordBatches(batches));
    return writer_->WriteTable(*table);
  }

  Status Finish(WriteStats* out_stats = nullptr) {
    RETURN_NOT_OK(writer_->Close());
    if (out_stats) {
      *out_stats = writer_->stats();
    }
    return sink_->Close();
  }

  virtual Status ReadBatches(const IpcReadOptions& options,
                             RecordBatchVector* out_batches,
                             ReadStats* out_stats = nullptr,
                             MetadataVector* out_metadata_list = nullptr) {
    auto buf_reader = std::make_shared<io::BufferReader>(buffer_);
    ARROW_ASSIGN_OR_RAISE(auto reader, RecordBatchStreamReader::Open(buf_reader, options))
    if (out_metadata_list) {
      while (true) {
        ARROW_ASSIGN_OR_RAISE(auto chunk_with_metadata, reader->ReadNext());
        if (chunk_with_metadata.batch == nullptr) {
          break;
        }
        out_batches->push_back(chunk_with_metadata.batch);
        out_metadata_list->push_back(chunk_with_metadata.custom_metadata);
      }
    } else {
      ARROW_ASSIGN_OR_RAISE(*out_batches, reader->ToRecordBatches());
    }

    if (out_stats) {
      *out_stats = reader->stats();
    }
    return Status::OK();
  }

  Status ReadSchema(std::shared_ptr<Schema>* out) {
    return ReadSchema(ipc::IpcReadOptions::Defaults(), out);
  }