替换所有block的实现

main.m

//
//  main.m
//  TestObjc
//
//  Created by Skifary on 14/03/2018.
//  Copyright © 2018 skifary. All rights reserved.
//

#import <Foundation/Foundation.h>

#import "fishhook.h"

typedef struct __block_impl {
    void *isa;
    int Flags;
    int Reserved;
    void *FuncPtr;
}__block_impl;

static void (*orig_func)(void *v ,int i, NSString *str);

void hookFunc(void *v ,int i, NSString *str) {
    NSLog(@"%d,%@", i, str);
    orig_func(v,i,str);
}

void HookBlockToPrintArguments(id blk) {
    __block_impl *ptr = (__bridge __block_impl *)blk;
    orig_func = ptr->FuncPtr;
    ptr->FuncPtr = &hookFunc;
}

#pragma mark - 第三题实现部分

static id (*orig_objc_retainBlock)(id);

id hook_objc_retainBlock(id blk) {
    
    id retainBlk = orig_objc_retainBlock(blk);
    
    // 因为retain会多次调动
    // 这里可以给blk添加一个属性 如果被hook过就不用继续hook
    // 因为这里只是一个测试例子 就不做这么麻烦了
    if (true) {
        HookBlockToPrintArguments(blk);
    }
    return retainBlk;
}

void HookEveryBlockToPrintArguments() {
    rebind_symbols((struct rebinding[1]){{"objc_retainBlock", hook_objc_retainBlock, (void *)&orig_objc_retainBlock}}, 1);
}

int main(int argc, const char * argv[]) {

    HookEveryBlockToPrintArguments();
    
    void (^blk)(int, NSString *) = ^void(int i, NSString *str) {
        NSLog(@"original invoke");
    };

    blk(1,@"aaa");
    
    return 0;
}