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/*******************************************************************************
JRSwizzle.m
Copyright (c) 2007 Jonathan 'Wolf' Rentzsch: <http://rentzsch.com>
Some rights reserved: <http://opensource.org/licenses/mit-license.php>

***************************************************************************/

#import "JRSwizzle.h"
#import <objc/objc-class.h>

#define SetNSError(ERROR_VAR, FORMAT,...) \
if (ERROR_VAR) { \
NSString *errStr = [@"+[NSObject(JRSwizzle) jr_swizzleMethod:withMethod:error:]: " stringByAppendingFormat:FORMAT,##__VA_ARGS__]; \
*ERROR_VAR = [NSError errorWithDomain:@"NSCocoaErrorDomain" \
code:-1 \
userInfo:[NSDictionary dictionaryWithObject:errStr forKey:NSLocalizedDescriptionKey]]; \
}

@implementation NSObject (JRSwizzle)

+ (BOOL)jr_swizzleMethod:(SEL)origSel_ withMethod:(SEL)altSel_ error:(NSError**)error_ {
#if OBJC_API_VERSION >= 2
Method origMethod = class_getInstanceMethod(self, origSel_);
if (!origMethod) {
SetNSError(error_, @"original method %@ not found for class %@", NSStringFromSelector(origSel_), [self className]);
return NO;
}

Method altMethod = class_getInstanceMethod(self, altSel_);
if (!altMethod) {
SetNSError(error_, @"alternate method %@ not found for class %@", NSStringFromSelector(altSel_), [self className]);
return NO;
}

class_addMethod(self,
origSel_,
class_getMethodImplementation(self, origSel_),
method_getTypeEncoding(origMethod));
class_addMethod(self,
altSel_,
class_getMethodImplementation(self, altSel_),
method_getTypeEncoding(altMethod));

method_exchangeImplementations(class_getInstanceMethod(self, origSel_), class_getInstanceMethod(self, altSel_));
return YES;
#else
// Scan for non-inherited methods.
Method directOriginalMethod = NULL, directAlternateMethod = NULL;

void *iterator = NULL;
struct objc_method_list *mlist = class_nextMethodList(self, &iterator);
while (mlist) {
int method_index = 0;
for (; method_index < mlist->method_count; method_index++) {
if (mlist->method_list[method_index].method_name == origSel_) {
assert(!directOriginalMethod);
directOriginalMethod = &mlist->method_list[method_index];
}
if (mlist->method_list[method_index].method_name == altSel_) {
assert(!directAlternateMethod);
directAlternateMethod = &mlist->method_list[method_index];
}
}
mlist = class_nextMethodList(self, &iterator);
}

// If either method is inherited, copy it up to the target class to make it non-inherited.
if (!directOriginalMethod || !directAlternateMethod) {
Method inheritedOriginalMethod = NULL, inheritedAlternateMethod = NULL;
if (!directOriginalMethod) {
inheritedOriginalMethod = class_getInstanceMethod(self, origSel_);
if (!inheritedOriginalMethod) {
SetNSError(error_, @"original method %@ not found for class %@", NSStringFromSelector(origSel_), [self className]);
return NO;
}
}
if (!directAlternateMethod) {
inheritedAlternateMethod = class_getInstanceMethod(self, altSel_);
if (!inheritedAlternateMethod) {
SetNSError(error_, @"alternate method %@ not found for class %@", NSStringFromSelector(altSel_), [self className]);
return NO;
}
}

int hoisted_method_count = !directOriginalMethod && !directAlternateMethod ? 2 : 1;
struct objc_method_list *hoisted_method_list = malloc(sizeof(struct objc_method_list) + (sizeof(struct objc_method)*(hoisted_method_count-1)));
hoisted_method_list->method_count = hoisted_method_count;
Method hoisted_method = hoisted_method_list->method_list;

if (!directOriginalMethod) {
bcopy(inheritedOriginalMethod, hoisted_method, sizeof(struct objc_method));
directOriginalMethod = hoisted_method++;
}
if (!directAlternateMethod) {
bcopy(inheritedAlternateMethod, hoisted_method, sizeof(struct objc_method));
directAlternateMethod = hoisted_method;
}
class_addMethods(self, hoisted_method_list);
}

// Swizzle.
IMP temp = directOriginalMethod->method_imp;
directOriginalMethod->method_imp = directAlternateMethod->method_imp;
directAlternateMethod->method_imp = temp;

return YES;
#endif
}

+ (BOOL)jr_swizzleClassMethod:(SEL)origSel_ withClassMethod:(SEL)altSel_ error:(NSError**)error_ {
assert(0);
return NO;
}

@end
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