iOS-自定义objc_class验证cache_t

根据类objc_class的结构，自定义lg_objc_class，来验证cache_t缓存，前提是了解原本cache_t的结构。

#import <Foundation/Foundation.h>
#import "LGPerson.h"
#import <objc/runtime.h>

typedef uint32_t mask_t;
typedef uintptr_t cache_key_t;
typedef unsigned long  uintptr_t;

struct lg_bucket_t {
    IMP _imp;
    cache_key_t _key;
};

struct lg_cache_t {
    struct lg_bucket_t *_buckets;
    mask_t _mask;
    mask_t _occupied;
};

struct lg_class_data_bits_t {
    uintptr_t bits;
};

struct lg_objc_class {
    Class ISA;
    Class superclass;
    struct lg_cache_t cache;             // formerly cache pointer and vtable
    struct lg_class_data_bits_t bits;    // class_rw_t * plus custom rr/alloc flags
};

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        LGPerson *person = [[LGPerson alloc] init];
        Class pClass = [LGPerson class];

        [person sayHello];
        [person sayCode];
        [person sayNB]; 

        struct lg_objc_class *lg_pClass = (__bridge struct lg_objc_class *)(pClass);
        for (mask_t i = 0; i<lg_pClass->cache._mask; i++) {
            struct lg_bucket_t bucket = lg_pClass->cache._buckets[i];
            NSLog(@"%lu - %p",bucket._key,bucket._imp);
        }
        NSLog(@"%@ - %p",person,pClass);

    }
    return 0;
}

使用此方法，可快速打印了解缓存的方法信息。