Add ScopedObjCClassSwizzler in base/mac, absorbs objc_method_swizzle and ScopedClassSwizzler

base/mac/scoped_objc_class_swizzler_unittest.mm

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "base/mac/scoped_objc_class_swizzler.h"
+
+#import "base/mac/scoped_nsobject.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+@interface ObjCClassSwizzlerTestOne : NSObject
++ (NSInteger)function;
+- (NSInteger)method;
+- (NSInteger)modifier;
+@end
+
+@interface ObjCClassSwizzlerTestTwo : NSObject
++ (NSInteger)function;
+- (NSInteger)method;
+- (NSInteger)modifier;
+@end
+
+@implementation ObjCClassSwizzlerTestOne : NSObject
+
++ (NSInteger)function {
+  return 10;
+}
+
+- (NSInteger)method {
+  // Multiply by a modifier to ensure |self| in a swizzled implementation
+  // refers to the original object.
+  return 1 * [self modifier];
+}
+
+- (NSInteger)modifier {
+  return 3;
+}
+
+@end
+
+@implementation ObjCClassSwizzlerTestTwo : NSObject
+
++ (NSInteger)function {
+  return 20;
+}
+
+- (NSInteger)method {
+  return 2 * [self modifier];
+}
+
+- (NSInteger)modifier {
+  return 7;
+}
+
+@end
+
+namespace base {
+namespace mac {
+
+TEST(ObjCClassSwizzlerTest, SwizzleInstanceMethods) {
+  base::scoped_nsobject<ObjCClassSwizzlerTestOne> object_one(
+      [[ObjCClassSwizzlerTestOne alloc] init]);
+  base::scoped_nsobject<ObjCClassSwizzlerTestTwo> object_two(
+      [[ObjCClassSwizzlerTestTwo alloc] init]);
+  EXPECT_EQ(3, [object_one method]);
+  EXPECT_EQ(14, [object_two method]);
+
+  {
+    base::mac::ScopedObjCClassSwizzler swizzler(
+        [ObjCClassSwizzlerTestOne class],
+        [ObjCClassSwizzlerTestTwo class],
+        @selector(method));
+    EXPECT_EQ(6, [object_one method]);
+    EXPECT_EQ(7, [object_two method]);
+
+    IMP original = swizzler.GetOriginalImplementation();
+    id expected_result = reinterpret_cast<id>(3);
+    EXPECT_EQ(expected_result, original(object_one, @selector(method)));
+  }
+
+  EXPECT_EQ(3, [object_one method]);
+  EXPECT_EQ(14, [object_two method]);
+}
+
+TEST(ObjCClassSwizzlerTest, SwizzleClassMethods) {
+  EXPECT_EQ(10, [ObjCClassSwizzlerTestOne function]);
+  EXPECT_EQ(20, [ObjCClassSwizzlerTestTwo function]);
+
+  {
+    base::mac::ScopedObjCClassSwizzler swizzler(
+        [ObjCClassSwizzlerTestOne class],
+        [ObjCClassSwizzlerTestTwo class],
+        @selector(function));
+    EXPECT_EQ(20, [ObjCClassSwizzlerTestOne function]);
+    EXPECT_EQ(10, [ObjCClassSwizzlerTestTwo function]);
+
+    IMP original = swizzler.GetOriginalImplementation();
+    id expected_result = reinterpret_cast<id>(10);
+    EXPECT_EQ(expected_result, original(nil, @selector(function)));
+  }
+
+  EXPECT_EQ(10, [ObjCClassSwizzlerTestOne function]);
+  EXPECT_EQ(20, [ObjCClassSwizzlerTestTwo function]);
+}
+
+}  // namespace mac
+}  // namespace base