PoseAsClass.mm 3.04 KB
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/*
 * Copyright (C) 2013 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "PoseAsClass.h"

#import <objc/runtime.h>
#import <wtf/Assertions.h>

static void swizzleAllMethods(Class imposter, Class original)
{
    unsigned imposterMethodCount;
    Method* imposterMethods = class_copyMethodList(imposter, &imposterMethodCount);

    unsigned originalMethodCount;
    Method* originalMethods = class_copyMethodList(original, &originalMethodCount);

    for (unsigned i = 0; i < imposterMethodCount; i++) {
        SEL imposterMethodName = method_getName(imposterMethods[i]);

        // Attempt to add the method to the original class.  If it fails, the method already exists and we should
        // instead exchange the implementations.
        if (class_addMethod(original, imposterMethodName, method_getImplementation(imposterMethods[i]), method_getTypeEncoding(imposterMethods[i])))
            continue;

        unsigned j = 0;
        for (; j < originalMethodCount; j++) {
            SEL originalMethodName = method_getName(originalMethods[j]);
            if (sel_isEqual(imposterMethodName, originalMethodName))
                break;
        }

        // If class_addMethod failed above then the method must exist on the original class.
        ASSERT(j < originalMethodCount);
        method_exchangeImplementations(imposterMethods[i], originalMethods[j]);
    }

    free(imposterMethods);
    free(originalMethods);
}

void poseAsClass(const char* imposter, const char* original)
{
    Class imposterClass = objc_getClass(imposter);
    Class originalClass = objc_getClass(original);

    // Swizzle instance methods
    swizzleAllMethods(imposterClass, originalClass);
    // and then class methods
    swizzleAllMethods(object_getClass(imposterClass), object_getClass(originalClass));
}