Function MakeDecodingGenerator

cpp/src/arrow/json/reader.cc:333–351

Reads from a source iterator, completes the subsequent decode task on the calling thread. This is only really used for compatibility with the async pipeline when CPU threading is disabled

// thread. This is only really used for compatibility with the async pipeline when CPU
// threading is disabled
AsyncGenerator<DecodedBlock> MakeDecodingGenerator(
    Iterator<ChunkedBlock> source,
    std::function<Result<DecodedBlock>(const ChunkedBlock&)> decoder) {
  struct State {
    Iterator<ChunkedBlock> source;
    std::function<Result<DecodedBlock>(const ChunkedBlock&)> decoder;
  } state{std::move(source), std::move(decoder)};
  return [state = std::make_shared<State>(std::move(state))] {
    auto maybe_block = state->source.Next();
    if (!maybe_block.ok()) {
      return Future<DecodedBlock>::MakeFinished(maybe_block.status());
    }
    const auto& block = maybe_block.ValueUnsafe();
    if (IsIterationEnd(block)) {
      return ToFuture(IterationEnd<DecodedBlock>());
    }
    return ToFuture(state->decoder(block));
  };
}

class StreamingReaderImpl : public StreamingReader {
 public: