Allow to (std::)Swap two pointers.

Author: ylavic

include/rapidjson/pointer.h

@@ -200,6 +200,36 @@ class GenericPointer {
         return *this;
     }
 
+    //! Swap the content of this pointer with an other.
+    /*!
+        \param other The pointer to swap with.
+        \note Constant complexity.
+    */
+    GenericPointer& Swap(GenericPointer& other) RAPIDJSON_NOEXCEPT {
+        internal::Swap(allocator_, other.allocator_);
+        internal::Swap(ownAllocator_, other.ownAllocator_);
+        internal::Swap(nameBuffer_, other.nameBuffer_);
+        internal::Swap(tokens_, other.tokens_);
+        internal::Swap(tokenCount_, other.tokenCount_);
+        internal::Swap(parseErrorOffset_, other.parseErrorOffset_);
+        internal::Swap(parseErrorCode_, other.parseErrorCode_);
+        return *this;
+    }
+
+    //! free-standing swap function helper
+    /*!
+        Helper function to enable support for common swap implementation pattern based on \c std::swap:
+        \code
+        void swap(MyClass& a, MyClass& b) {
+            using std::swap;
+            swap(a.pointer, b.pointer);
+            // ...
+        }
+        \endcode
+        \see Swap()
+     */
+    friend inline void swap(GenericPointer& a, GenericPointer& b) RAPIDJSON_NOEXCEPT { a.Swap(b); }
+
     //@}
 
     //!@name Append token

test/unittest/pointertest.cpp

@@ -529,6 +529,36 @@ TEST(Pointer, Assignment) {
     }
 }
 
+TEST(Pointer, Swap) {
+	Pointer p("/foo/0");
+	Pointer q(&p.GetAllocator());
+
+	q.Swap(p);
+	EXPECT_EQ(&q.GetAllocator(), &p.GetAllocator());
+	EXPECT_TRUE(p.IsValid());
+	EXPECT_TRUE(q.IsValid());
+	EXPECT_EQ(0u, p.GetTokenCount());
+	EXPECT_EQ(2u, q.GetTokenCount());
+	EXPECT_EQ(3u, q.GetTokens()[0].length);
+	EXPECT_STREQ("foo", q.GetTokens()[0].name);
+	EXPECT_EQ(1u, q.GetTokens()[1].length);
+	EXPECT_STREQ("0", q.GetTokens()[1].name);
+	EXPECT_EQ(0u, q.GetTokens()[1].index);
+
+    // std::swap compatibility
+	std::swap(p, q);
+	EXPECT_EQ(&p.GetAllocator(), &q.GetAllocator());
+	EXPECT_TRUE(q.IsValid());
+	EXPECT_TRUE(p.IsValid());
+	EXPECT_EQ(0u, q.GetTokenCount());
+	EXPECT_EQ(2u, p.GetTokenCount());
+	EXPECT_EQ(3u, p.GetTokens()[0].length);
+	EXPECT_STREQ("foo", p.GetTokens()[0].name);
+	EXPECT_EQ(1u, p.GetTokens()[1].length);
+	EXPECT_STREQ("0", p.GetTokens()[1].name);
+	EXPECT_EQ(0u, p.GetTokens()[1].index);
+}
+
 TEST(Pointer, Append) {
     {
         Pointer p;
@@ -867,7 +897,7 @@ TEST(Pointer, Set_NoAllocator) {
 #endif
 }
 
-TEST(Pointer, Swap) {
+TEST(Pointer, Swap_Value) {
     Document d;
     d.Parse(kJson);
     Document::AllocatorType& a = d.GetAllocator();
@@ -876,7 +906,7 @@ TEST(Pointer, Swap) {
     EXPECT_STREQ("bar", d["foo"][1].GetString());
 }
 
-TEST(Pointer, Swap_NoAllocator) {
+TEST(Pointer, Swap_Value_NoAllocator) {
     Document d;
     d.Parse(kJson);
     Pointer("/foo/0").Swap(d, *Pointer("/foo/1").Get(d));