Swizzletastic

gistfile1.txt

#include <objc/runtime.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "SwizzleMyNizzleProtocol.h"

BOOL SwizzleMethod(Class _class, SEL origSel, IMP altImp, char *prefix) {
    if (_class == NULL || origSel == NULL || altImp == NULL) {
        fprintf(stderr, "[Error] Class, SEL or IMP is NULL");
		return NO;
    }
    
    Method origMethod = class_getInstanceMethod(_class, origSel);
    if (origMethod == NULL) {
        fprintf(stderr, "[Error] origMethod not found");
        return NO;
    }
    
    if (prefix == NULL) {
        prefix = "orig_";
    }
    
    const char *type = method_getTypeEncoding(origMethod);
    
    const char *origName = sel_getName(origSel);
    
    size_t namelen = strlen(origName);
    size_t fixlen = strlen(prefix);
    
    char *altName;
    altName = (char *)malloc((fixlen + namelen + 1) * sizeof(char));
    memcpy(altName, prefix, fixlen);
    memcpy(altName + fixlen, origName, namelen + 1);
    
    SEL altSel = sel_registerName(altName);
    
    if (!class_addMethod(_class, origSel, class_getMethodImplementation(_class, origSel), type)) {
        fprintf(stderr, "[Error] Failed to add origMethod");
        return NO;
    }
    
    if (!class_addMethod(_class, altSel, altImp, type)) {
        fprintf(stderr, "[Error] Failed to add altMethod");
        return NO;
    }
    
    method_exchangeImplementations(class_getInstanceMethod(_class, origSel), class_getInstanceMethod(_class, altSel));
    return YES;
}