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ext/libpqxx-7.7.3/include/pqxx/internal/stream_iterator.hxx

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+/** Stream iterators.
+ *
+ * Copyright (c) 2000-2022, Jeroen T. Vermeulen.
+ *
+ * See COPYING for copyright license.  If you did not receive a file called
+ * COPYING with this source code, please notify the distributor of this
+ * mistake, or contact the author.
+ */
+#ifndef PQXX_H_STREAM_ITERATOR
+#define PQXX_H_STREAM_ITERATOR
+
+#include <memory>
+
+namespace pqxx
+{
+class stream_from;
+}
+
+
+namespace pqxx::internal
+{
+// C++20: Replace with generator?
+/// Input iterator for stream_from.
+/** Just barely enough to support range-based "for" loops.  Don't assume that
+ * any of the usual behaviour works beyond that.
+ */
+template<typename... TYPE> class stream_input_iterator
+{
+public:
+  using value_type = std::tuple<TYPE...>;
+
+  /// Construct an "end" iterator.
+  stream_input_iterator() = default;
+
+  explicit stream_input_iterator(stream_from &home) : m_home(&home)
+  {
+    advance();
+  }
+  stream_input_iterator(stream_input_iterator const &) = default;
+
+  stream_input_iterator &operator++()
+  {
+    advance();
+    return *this;
+  }
+
+  value_type const &operator*() const { return m_value; }
+
+  /// Comparison only works for comparing to end().
+  bool operator==(stream_input_iterator const &rhs) const
+  {
+    return m_home == rhs.m_home;
+  }
+  /// Comparison only works for comparing to end().
+  bool operator!=(stream_input_iterator const &rhs) const
+  {
+    return not(*this == rhs);
+  }
+
+private:
+  void advance()
+  {
+    if (m_home == nullptr)
+      throw usage_error{"Moving stream_from iterator beyond end()."};
+    if (not((*m_home) >> m_value))
+      m_home = nullptr;
+  }
+
+  stream_from *m_home{nullptr};
+  value_type m_value;
+};
+
+
+// C++20: Replace with generator?
+/// Iteration over a @ref stream_from.
+template<typename... TYPE> class stream_input_iteration
+{
+public:
+  using iterator = stream_input_iterator<TYPE...>;
+  explicit stream_input_iteration(stream_from &home) : m_home{home} {}
+  iterator begin() const { return iterator{m_home}; }
+  iterator end() const { return {}; }
+
+private:
+  stream_from &m_home;
+};
+
+
+// C++20: Replace with generator?
+/// Iteration over a @ref stream_from, deleting it once done.
+template<typename... TYPE> class owning_stream_input_iteration
+{
+public:
+  using iterator = stream_input_iterator<TYPE...>;
+  explicit owning_stream_input_iteration(std::unique_ptr<stream_from> &&home) :
+          m_home{std::move(home)}
+  {}
+  iterator begin() const { return iterator{*m_home.get()}; }
+  iterator end() const { return {}; }
+
+private:
+  std::unique_ptr<stream_from> m_home;
+};
+} // namespace pqxx::internal
+#endif