Implement additional set operators: STLSetUnion, STLSetIntersection a…

…nd STLIncludes.

BUG=336824
TBR=willchan@chromium.org, jyasskin@chromium.org
(lgtm'ed in https://codereview.chromium.org/145663004/)

Review URL: https://codereview.chromium.org/148183012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247711 0039d316-1c4b-4281-b951-d872f2087c98

base/stl_util.h

@@ -201,9 +201,11 @@ namespace base {
 // Returns true if the container is sorted.
 template <typename Container>
 bool STLIsSorted(const Container& cont) {
-  return std::adjacent_find(cont.begin(), cont.end(),
-                            std::greater<typename Container::value_type>())
-      == cont.end();
+  // Note: Use reverse iterator on container to ensure we only require
+  // value_type to implement operator<.
+  return std::adjacent_find(cont.rbegin(), cont.rend(),
+                            std::less<typename Container::value_type>())
+      == cont.rend();
 }
 
 // Returns a new ResultType containing the difference of two sorted containers.
@@ -218,6 +220,41 @@ ResultType STLSetDifference(const Arg1& a1, const Arg2& a2) {
   return difference;
 }
 
+// Returns a new ResultType containing the union of two sorted containers.
+template <typename ResultType, typename Arg1, typename Arg2>
+ResultType STLSetUnion(const Arg1& a1, const Arg2& a2) {
+  DCHECK(STLIsSorted(a1));
+  DCHECK(STLIsSorted(a2));
+  ResultType result;
+  std::set_union(a1.begin(), a1.end(),
+                 a2.begin(), a2.end(),
+                 std::inserter(result, result.end()));
+  return result;
+}
+
+// Returns a new ResultType containing the intersection of two sorted
+// containers.
+template <typename ResultType, typename Arg1, typename Arg2>
+ResultType STLSetIntersection(const Arg1& a1, const Arg2& a2) {
+  DCHECK(STLIsSorted(a1));
+  DCHECK(STLIsSorted(a2));
+  ResultType result;
+  std::set_intersection(a1.begin(), a1.end(),
+                        a2.begin(), a2.end(),
+                        std::inserter(result, result.end()));
+  return result;
+}
+
+// Returns true if the sorted container |a1| contains all elements of the sorted
+// container |a2|.
+template <typename Arg1, typename Arg2>
+bool STLIncludes(const Arg1& a1, const Arg2& a2) {
+  DCHECK(STLIsSorted(a1));
+  DCHECK(STLIsSorted(a2));
+  return std::includes(a1.begin(), a1.end(),
+                       a2.begin(), a2.end());
+}
+
 }  // namespace base
 
 #endif  // BASE_STL_UTIL_H_

base/stl_util_unittest.cc

@@ -8,6 +8,28 @@
 
 #include "testing/gtest/include/gtest/gtest.h"
 
+namespace {
+
+// Used as test case to ensure the various base::STLXxx functions don't require
+// more than operators "<" and "==" on values stored in containers.
+class ComparableValue {
+ public:
+  explicit ComparableValue(int value) : value_(value) {}
+
+  bool operator==(const ComparableValue& rhs) const {
+    return value_ == rhs.value_;
+  }
+
+  bool operator<(const ComparableValue& rhs) const {
+    return value_ < rhs.value_;
+  }
+
+ private:
+  int value_;
+};
+
+}
+
 namespace base {
 namespace {
 
@@ -20,6 +42,14 @@ TEST(STLUtilTest, STLIsSorted) {
     EXPECT_TRUE(STLIsSorted(set));
   }
 
+  {
+    std::set<ComparableValue> set;
+    set.insert(ComparableValue(24));
+    set.insert(ComparableValue(1));
+    set.insert(ComparableValue(12));
+    EXPECT_TRUE(STLIsSorted(set));
+  }
+
   {
     std::vector<int> vector;
     vector.push_back(1);
@@ -78,5 +108,135 @@ TEST(STLUtilTest, STLSetDifference) {
   }
 }
 
+TEST(STLUtilTest, STLSetUnion) {
+  std::set<int> a1;
+  a1.insert(1);
+  a1.insert(2);
+  a1.insert(3);
+  a1.insert(4);
+
+  std::set<int> a2;
+  a2.insert(3);
+  a2.insert(4);
+  a2.insert(5);
+  a2.insert(6);
+  a2.insert(7);
+
+  {
+    std::set<int> result;
+    result.insert(1);
+    result.insert(2);
+    result.insert(3);
+    result.insert(4);
+    result.insert(5);
+    result.insert(6);
+    result.insert(7);
+    EXPECT_EQ(result, STLSetUnion<std::set<int> >(a1, a2));
+  }
+
+  {
+    std::set<int> result;
+    result.insert(1);
+    result.insert(2);
+    result.insert(3);
+    result.insert(4);
+    result.insert(5);
+    result.insert(6);
+    result.insert(7);
+    EXPECT_EQ(result, STLSetUnion<std::set<int> >(a2, a1));
+  }
+
+  {
+    std::vector<int> result;
+    result.push_back(1);
+    result.push_back(2);
+    result.push_back(3);
+    result.push_back(4);
+    result.push_back(5);
+    result.push_back(6);
+    result.push_back(7);
+    EXPECT_EQ(result, STLSetUnion<std::vector<int> >(a1, a2));
+  }
+
+  {
+    std::vector<int> result;
+    result.push_back(1);
+    result.push_back(2);
+    result.push_back(3);
+    result.push_back(4);
+    result.push_back(5);
+    result.push_back(6);
+    result.push_back(7);
+    EXPECT_EQ(result, STLSetUnion<std::vector<int> >(a2, a1));
+  }
+}
+
+TEST(STLUtilTest, STLSetIntersection) {
+  std::set<int> a1;
+  a1.insert(1);
+  a1.insert(2);
+  a1.insert(3);
+  a1.insert(4);
+
+  std::set<int> a2;
+  a2.insert(3);
+  a2.insert(4);
+  a2.insert(5);
+  a2.insert(6);
+  a2.insert(7);
+
+  {
+    std::set<int> result;
+    result.insert(3);
+    result.insert(4);
+    EXPECT_EQ(result, STLSetIntersection<std::set<int> >(a1, a2));
+  }
+
+  {
+    std::set<int> result;
+    result.insert(3);
+    result.insert(4);
+    EXPECT_EQ(result, STLSetIntersection<std::set<int> >(a2, a1));
+  }
+
+  {
+    std::vector<int> result;
+    result.push_back(3);
+    result.push_back(4);
+    EXPECT_EQ(result, STLSetIntersection<std::vector<int> >(a1, a2));
+  }
+
+  {
+    std::vector<int> result;
+    result.push_back(3);
+    result.push_back(4);
+    EXPECT_EQ(result, STLSetIntersection<std::vector<int> >(a2, a1));
+  }
+}
+
+TEST(STLUtilTest, STLIncludes) {
+  std::set<int> a1;
+  a1.insert(1);
+  a1.insert(2);
+  a1.insert(3);
+  a1.insert(4);
+
+  std::set<int> a2;
+  a2.insert(3);
+  a2.insert(4);
+
+  std::set<int> a3;
+  a3.insert(3);
+  a3.insert(4);
+  a3.insert(5);
+
+  EXPECT_TRUE(STLIncludes<std::set<int> >(a1, a2));
+  EXPECT_FALSE(STLIncludes<std::set<int> >(a1, a3));
+  EXPECT_FALSE(STLIncludes<std::set<int> >(a2, a1));
+  EXPECT_FALSE(STLIncludes<std::set<int> >(a2, a3));
+  EXPECT_FALSE(STLIncludes<std::set<int> >(a3, a1));
+  EXPECT_TRUE(STLIncludes<std::set<int> >(a3, a2));
+}
+
 }  // namespace
 }  // namespace base