Add UnorderedEqualsMatcher for vectors

Closes #1093

include/internal/catch_matchers_vector.h

@@ -10,10 +10,33 @@
 
 #include "catch_matchers.h"
 
+#include <algorithm>
+
 namespace Catch {
 namespace Matchers {
 
     namespace Vector {
+        namespace Detail {
+            template <typename InputIterator, typename T>
+            size_t count(InputIterator first, InputIterator last, T const& item) {
+                size_t cnt = 0;
+                for (; first != last; ++first) {
+                    if (*first == item) {
+                        ++cnt;
+                    }
+                }
+                return cnt;
+            }
+            template <typename InputIterator, typename T>
+            bool contains(InputIterator first, InputIterator last, T const& item) {
+                for (; first != last; ++first) {
+                    if (*first == item) {
+                        return true;
+                    }
+                }
+                return false;
+            }
+        }
 
         template<typename T>
         struct ContainsElementMatcher : MatcherBase<std::vector<T>> {
@@ -89,6 +112,46 @@ namespace Matchers {
             std::vector<T> const& m_comparator;
         };
 
+        template<typename T>
+        struct UnorderedEqualsMatcher : MatcherBase<std::vector<T>> {
+            UnorderedEqualsMatcher(std::vector<T> const& target) : m_target(target) {}
+            bool match(std::vector<T> const& vec) const override {
+                // Note: This is a reimplementation of std::is_permutation,
+                //       because I don't want to include <algorithm> inside the common path
+                if (m_target.size() != vec.size()) {
+                    return false;
+                }
+                auto lfirst = m_target.begin(), llast = m_target.end();
+                auto rfirst = vec.begin(), rlast = vec.end();
+                // Cut common prefix to optimize checking of permuted parts
+                while (lfirst != llast && *lfirst != *rfirst) {
+                    ++lfirst; ++rfirst;
+                }
+                if (lfirst == llast) {
+                    return true;
+                }
+
+                for (auto mid = lfirst; mid != llast; ++mid) {
+                    // Skip already counted items
+                    if (Detail::contains(lfirst, mid, *mid)) {
+                        continue;
+                    }
+                    size_t num_vec = Detail::count(rfirst, rlast, *mid);
+                    if (num_vec == 0 || Detail::count(lfirst, llast, *mid) != num_vec) {
+                        return false;
+                    }
+                }
+
+                return true;
+            }
+
+            std::string describe() const override {
+                return "UnorderedEquals: " + ::Catch::Detail::stringify(m_target);
+            }
+        private:
+            std::vector<T> const& m_target;
+        };
+
     } // namespace Vector
 
     // The following functions create the actual matcher objects.
@@ -109,6 +172,11 @@ namespace Matchers {
         return Vector::EqualsMatcher<T>( comparator );
     }
 
+    template<typename T>
+    Vector::UnorderedEqualsMatcher<T> UnorderedEquals(std::vector<T> const& target) {
+        return Vector::UnorderedEqualsMatcher<T>(target);
+    }
+
 } // namespace Matchers
 } // namespace Catch