Tengeneza dylib na sehemu ya __interpose (__DATA___interpose) (au sehemu iliyofungwa na S_INTERPOSING) inayojumuisha jozi za pointa za kazi zinazorejelea kazi za awali na zilizochukua nafasi.
Chaguo la mazingira la DYLD_PRINT_INTERPOSTING linaweza kutumika kudebugi interposing na litachapisha mchakato wa interpose.
Pia elewa kwamba interposing hutokea kati ya mchakato na maktaba zilizopakiwa, haitafanyi kazi na hifadhi ya maktaba iliyoshirikiwa.
Interposing ya Kisasa
Sasa pia ni iwezekanavyo kuingiza kazi kwa njia ya kisasa kwa kutumia kazi ya dyld_dynamic_interpose. Hii inaruhusu kuingiza kazi kwa njia ya programu wakati wa muda wa uendeshaji badala ya kufanya hivyo tu kutoka mwanzoni.
Inahitajika tu kuonyesha tuples ya kazi ya kuchukua nafasi na kazi mbadala.
Katika ObjectiveC hivi ndivyo mbinu inavyoitwa: [myClassInstance nameOfTheMethodFirstParam:param1 secondParam:param2]
Inahitajika kitu, mbinu na paramu. Na wakati mbinu inaitwa msg inatumwa kutumia kazi objc_msgSend: int i = ((int (*)(id, SEL, NSString *, NSString *))objc_msgSend)(someObject, @selector(method1p1:p2:), value1, value2);
Kitu ni someObject, mbinu ni @selector(method1p1:p2:) na hoja ni value1, value2.
Kufuatia miundo ya vitu, ni rahisi kufikia orodha ya mbinu ambapo majina na alama za nambari ya mbinu zinapatikana.
Tafadhali kumbuka kwamba kwa sababu mbinu na madarasa yanafikiwa kulingana na majina yao, habari hii imehifadhiwa kwenye faili ya binary, hivyo ni rahisi kuipata kwa kutumia otool -ov </path/bin> au class-dump </path/bin>
Kufikia mbinu za asili
Inawezekana kupata habari za mbinu kama jina, idadi ya paramu au anwani kama ilivyo kwenye mfano ufuatao:
// gcc -framework Foundation test.m -o test
#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>
int main() {
// Get class of the variable
NSString* str = @"This is an example";
Class strClass = [str class];
NSLog(@"str's Class name: %s", class_getName(strClass));
// Get parent class of a class
Class strSuper = class_getSuperclass(strClass);
NSLog(@"Superclass name: %@",NSStringFromClass(strSuper));
// Get information about a method
SEL sel = @selector(length);
NSLog(@"Selector name: %@", NSStringFromSelector(sel));
Method m = class_getInstanceMethod(strClass,sel);
NSLog(@"Number of arguments: %d", method_getNumberOfArguments(m));
NSLog(@"Implementation address: 0x%lx", (unsigned long)method_getImplementation(m));
// Iterate through the class hierarchy
NSLog(@"Listing methods:");
Class currentClass = strClass;
while (currentClass != NULL) {
unsigned int inheritedMethodCount = 0;
Method* inheritedMethods = class_copyMethodList(currentClass, &inheritedMethodCount);
NSLog(@"Number of inherited methods in %s: %u", class_getName(currentClass), inheritedMethodCount);
for (unsigned int i = 0; i < inheritedMethodCount; i++) {
Method method = inheritedMethods[i];
SEL selector = method_getName(method);
const char* methodName = sel_getName(selector);
unsigned long address = (unsigned long)method_getImplementation(m);
NSLog(@"Inherited method name: %s (0x%lx)", methodName, address);
}
// Free the memory allocated by class_copyMethodList
free(inheritedMethods);
currentClass = class_getSuperclass(currentClass);
}
// Other ways to call uppercaseString method
if([str respondsToSelector:@selector(uppercaseString)]) {
NSString *uppercaseString = [str performSelector:@selector(uppercaseString)];
NSLog(@"Uppercase string: %@", uppercaseString);
}
// Using objc_msgSend directly
NSString *uppercaseString2 = ((NSString *(*)(id, SEL))objc_msgSend)(str, @selector(uppercaseString));
NSLog(@"Uppercase string: %@", uppercaseString2);
// Calling the address directly
IMP imp = method_getImplementation(class_getInstanceMethod(strClass, @selector(uppercaseString))); // Get the function address
NSString *(*callImp)(id,SEL) = (typeof(callImp))imp; // Generates a function capable to method from imp
NSString *uppercaseString3 = callImp(str,@selector(uppercaseString)); // Call the method
NSLog(@"Uppercase string: %@", uppercaseString3);
return 0;
}