Method GetSegments

cpp/src/arrow/compute/row/grouper.cc:128–167

  }

  Result<std::vector<Segment>> GetSegments(const ExecSpan& batch) override {
    RETURN_NOT_OK(CheckForGetSegments(batch, {key_type_}));

    if (batch.length == 0) {
      return std::vector<Segment>{};
    }

    const auto& value = batch.values[0];
    DCHECK(is_fixed_width(*value.type()));

    std::vector<Segment> segments;
    const void* key_data;
    if (value.is_scalar()) {
      const auto& scalar = *value.scalar;
      DCHECK(scalar.is_valid);
      key_data = checked_cast<const PrimitiveScalarBase&>(scalar).data();
      bool extends = Extend(key_data);
      segments.push_back(MakeSegment(batch.length, 0, batch.length, extends));
    } else {
      DCHECK(value.is_array());
      const auto& array = value.array;
      DCHECK_EQ(array.GetNullCount(), 0);
      auto data = GetValuesAsBytes(array);
      int64_t byte_width = array.type->byte_width();
      int64_t offset = 0;
      bool extends = Extend(data);
      while (offset < array.length) {
        int64_t match_length = GetMatchLength(data + offset * byte_width, byte_width,
                                              data, offset, array.length);
        segments.push_back(MakeSegment(array.length, offset, match_length,
                                       offset == 0 ? extends : false));
        offset += match_length;
      }
      key_data = data + (array.length - 1) * byte_width;
    }

    SaveKeyData(key_data);

    return segments;
  }

 private:
  static const uint8_t* GetValuesAsBytes(const ArraySpan& data, int64_t offset = 0) {