import quincy beta 17.1.0

[ceph.git] / ceph / src / boost / libs / stl_interfaces / example / back_insert_iterator.cpp

diff --git a/ceph/src/boost/libs/stl_interfaces/example/back_insert_iterator.cpp b/ceph/src/boost/libs/stl_interfaces/example/back_insert_iterator.cpp
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+++ b/ceph/src/boost/libs/stl_interfaces/example/back_insert_iterator.cpp
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+// Copyright (C) 2019 T. Zachary Laine
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//[ back_insert_iterator
+#include <boost/stl_interfaces/iterator_interface.hpp>
+
+#include <algorithm>
+#include <vector>
+
+#include <cassert>
+
+
+// This is an output iterator that holds a reference to a container, and calls
+// push_back() on that container when it is written to, just like
+// std::back_insert_iterator.  This is not a lot less code to write than the
+// implementation of std::back_insert_iterator, but it demonstrates that
+// iterator_interface is flexible enough to handle this odd kind of iterator.
+template<typename Container>
+struct back_insert_iterator : boost::stl_interfaces::iterator_interface<
+                                  back_insert_iterator<Container>,
+                                  std::output_iterator_tag,
+                                  typename Container::value_type,
+                                  back_insert_iterator<Container> &>
+{
+    // For concept requirements.
+    back_insert_iterator() : c_(nullptr) {}
+
+    // Construct from a container.
+    explicit back_insert_iterator(Container & c) : c_(std::addressof(c)) {}
+
+    // When writing to *this, copy v into the container via push_back().
+    back_insert_iterator & operator=(typename Container::value_type const & v)
+    {
+        c_->push_back(v);
+        return *this;
+    }
+    // When writing to *this, move v into the container via push_back().
+    back_insert_iterator & operator=(typename Container::value_type && v)
+    {
+        c_->push_back(std::move(v));
+        return *this;
+    }
+
+    // Dereferencing *this just returns a reference to *this, so that the
+    // expression *it = value uses the operator=() overloads above.
+    back_insert_iterator & operator*() { return *this; }
+    // There is no underlying sequence over which we are iterating, so there's
+    // nowhere to go in next().  Do nothing.
+    back_insert_iterator & operator++() { return *this; }
+
+    using base_type = boost::stl_interfaces::iterator_interface<
+        back_insert_iterator<Container>,
+        std::output_iterator_tag,
+        typename Container::value_type,
+        back_insert_iterator<Container> &>;
+    using base_type::operator++;
+
+private:
+    Container * c_;
+};
+
+// A convenience function that creates a back_insert_iterator<Container>.
+template<typename Container>
+back_insert_iterator<Container> back_inserter(Container & c)
+{
+    return back_insert_iterator<Container>(c);
+}
+
+
+int main()
+{
+    std::vector<int> ints = {{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}};
+    std::vector<int> ints_copy;
+    std::copy(ints.begin(), ints.end(), ::back_inserter(ints_copy));
+    assert(ints_copy == ints);
+}
+//]