Class DecodingOperator

cpp/src/arrow/json/reader.cc:302–328

Callable object for parsing/converting individual JSON blocks. The class itself can be called concurrently but reads from the `DecodeContext` aren't synchronized

// Callable object for parsing/converting individual JSON blocks. The class itself can be
// called concurrently but reads from the `DecodeContext` aren't synchronized
class DecodingOperator {
 public:
  explicit DecodingOperator(std::shared_ptr<const DecodeContext> context)
      : context_(std::move(context)) {}

  Result<DecodedBlock> operator()(const ChunkedBlock& block) const {
    int64_t num_bytes;
    ARROW_ASSIGN_OR_RAISE(auto unconverted, ParseBlock(block, context_->parse_options(),
                                                       context_->pool(), &num_bytes));

    std::shared_ptr<ChunkedArrayBuilder> builder;
    RETURN_NOT_OK(MakeChunkedArrayBuilder(TaskGroup::MakeSerial(), context_->pool(),
                                          context_->promotion_graph(),
                                          context_->conversion_type(), &builder));
    builder->Insert(0, field("", unconverted->type()), unconverted);

    std::shared_ptr<ChunkedArray> chunked;
    RETURN_NOT_OK(builder->Finish(&chunked));
    ARROW_ASSIGN_OR_RAISE(
        auto batch, RecordBatch::FromStructArray(chunked->chunk(0), context_->pool()));

    return DecodedBlock{std::move(batch), num_bytes};
  }

 private:
  std::shared_ptr<const DecodeContext> context_;
};

// 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