streaming_result.hpp

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#pragma once
 
#include "lazy_result.hpp"
 
#include <optional>
#include <string>
#include <utility>
#include <vector>
 
namespace relx::result {
 
template <typename DataSource>
class StreamingResultSet {
public:
  class streaming_iterator {
  public:
    streaming_iterator(DataSource& source, bool at_end = false)
        : source_(source), current_row_(), at_end_(at_end) {
      if (!at_end_) {
        advance();
      }
    }
 
    LazyRow operator*() const { return current_row_; }
 
    streaming_iterator& operator++() {
      advance();
      return *this;
    }
 
    bool operator!=(const streaming_iterator& other) const { return at_end_ != other.at_end_; }
 
  private:
    DataSource& source_;
    LazyRow current_row_;
    bool at_end_;
 
    void advance() {
      auto next_row_data = source_.get_next_row();
      if (next_row_data) {
        current_row_ = LazyRow(std::move(*next_row_data), source_.get_column_names());
      } else {
        at_end_ = true;
      }
    }
  };
 
  StreamingResultSet(DataSource source) : source_(std::move(source)) {}
 
  streaming_iterator begin() { return streaming_iterator(source_); }
 
  streaming_iterator end() { return streaming_iterator(source_, true); }
 
private:
  DataSource source_;
};
 
}  // namespace relx::result