ObjC源码解读之一

本系列主要用来解读OC开放源码：objc

NSObject的实现内容

@implementation NSObject

+ (void)initialize {
}

+ (id)self {
    return (id)self;
}

- (id)self {
    return self;
}

+ (Class)class {
    return self;
}

- (Class)class {
    return object_getClass(self);
}

+ (Class)superclass {
    return self->superclass;
}

- (Class)superclass {
    return [self class]->superclass;
}

+ (BOOL)isMemberOfClass:(Class)cls {
    return self->ISA() == cls;
}

- (BOOL)isMemberOfClass:(Class)cls {
    return [self class] == cls;
}

+ (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = self->ISA(); tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

- (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = [self class]; tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

+ (BOOL)isSubclassOfClass:(Class)cls {
    for (Class tcls = self; tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

+ (BOOL)isAncestorOfObject:(NSObject *)obj {
    for (Class tcls = [obj class]; tcls; tcls = tcls->superclass) {
        if (tcls == self) return YES;
    }
    return NO;
}

+ (BOOL)instancesRespondToSelector:(SEL)sel {
    return class_respondsToSelector_inst(nil, sel, self);
}

+ (BOOL)respondsToSelector:(SEL)sel {
    return class_respondsToSelector_inst(self, sel, self->ISA());
}

- (BOOL)respondsToSelector:(SEL)sel {
    return class_respondsToSelector_inst(self, sel, [self class]);
}

+ (BOOL)conformsToProtocol:(Protocol *)protocol {
    if (!protocol) return NO;
    for (Class tcls = self; tcls; tcls = tcls->superclass) {
        if (class_conformsToProtocol(tcls, protocol)) return YES;
    }
    return NO;
}

- (BOOL)conformsToProtocol:(Protocol *)protocol {
    if (!protocol) return NO;
    for (Class tcls = [self class]; tcls; tcls = tcls->superclass) {
        if (class_conformsToProtocol(tcls, protocol)) return YES;
    }
    return NO;
}

+ (NSUInteger)hash {
    return _objc_rootHash(self);
}

- (NSUInteger)hash {
    return _objc_rootHash(self);
}

+ (BOOL)isEqual:(id)obj {
    return obj == (id)self;
}

- (BOOL)isEqual:(id)obj {
    return obj == self;
}


+ (BOOL)isFault {
    return NO;
}

- (BOOL)isFault {
    return NO;
}

+ (BOOL)isProxy {
    return NO;
}

- (BOOL)isProxy {
    return NO;
}


+ (IMP)instanceMethodForSelector:(SEL)sel {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return class_getMethodImplementation(self, sel);
}

+ (IMP)methodForSelector:(SEL)sel {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return object_getMethodImplementation((id)self, sel);
}

- (IMP)methodForSelector:(SEL)sel {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return object_getMethodImplementation(self, sel);
}

+ (BOOL)resolveClassMethod:(SEL)sel {
    return NO;
}

+ (BOOL)resolveInstanceMethod:(SEL)sel {
    return NO;
}

// Replaced by CF (throws an NSException)
+ (void)doesNotRecognizeSelector:(SEL)sel {
    _objc_fatal("+[%s %s]: unrecognized selector sent to instance %p", 
                class_getName(self), sel_getName(sel), self);
}

// Replaced by CF (throws an NSException)
- (void)doesNotRecognizeSelector:(SEL)sel {
    _objc_fatal("-[%s %s]: unrecognized selector sent to instance %p", 
                object_getClassName(self), sel_getName(sel), self);
}


+ (id)performSelector:(SEL)sel {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return ((id(*)(id, SEL))objc_msgSend)((id)self, sel);
}

+ (id)performSelector:(SEL)sel withObject:(id)obj {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return ((id(*)(id, SEL, id))objc_msgSend)((id)self, sel, obj);
}

+ (id)performSelector:(SEL)sel withObject:(id)obj1 withObject:(id)obj2 {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return ((id(*)(id, SEL, id, id))objc_msgSend)((id)self, sel, obj1, obj2);
}

- (id)performSelector:(SEL)sel {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return ((id(*)(id, SEL))objc_msgSend)(self, sel);
}

- (id)performSelector:(SEL)sel withObject:(id)obj {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return ((id(*)(id, SEL, id))objc_msgSend)(self, sel, obj);
}

- (id)performSelector:(SEL)sel withObject:(id)obj1 withObject:(id)obj2 {
    if (!sel) [self doesNotRecognizeSelector:sel];
    return ((id(*)(id, SEL, id, id))objc_msgSend)(self, sel, obj1, obj2);
}


// Replaced by CF (returns an NSMethodSignature)
+ (NSMethodSignature *)instanceMethodSignatureForSelector:(SEL)sel {
    _objc_fatal("+[NSObject instanceMethodSignatureForSelector:] "
                "not available without CoreFoundation");
}

// Replaced by CF (returns an NSMethodSignature)
+ (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
    _objc_fatal("+[NSObject methodSignatureForSelector:] "
                "not available without CoreFoundation");
}

// Replaced by CF (returns an NSMethodSignature)
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
    _objc_fatal("-[NSObject methodSignatureForSelector:] "
                "not available without CoreFoundation");
}

+ (void)forwardInvocation:(NSInvocation *)invocation {
    [self doesNotRecognizeSelector:(invocation ? [invocation selector] : 0)];
}

- (void)forwardInvocation:(NSInvocation *)invocation {
    [self doesNotRecognizeSelector:(invocation ? [invocation selector] : 0)];
}

+ (id)forwardingTargetForSelector:(SEL)sel {
    return nil;
}

- (id)forwardingTargetForSelector:(SEL)sel {
    return nil;
}


// Replaced by CF (returns an NSString)
+ (NSString *)description {
    return nil;
}

// Replaced by CF (returns an NSString)
- (NSString *)description {
    return nil;
}

+ (NSString *)debugDescription {
    return [self description];
}

- (NSString *)debugDescription {
    return [self description];
}


+ (id)new {
    return [callAlloc(self, false/*checkNil*/) init];
}

+ (id)retain {
    return (id)self;
}

// Replaced by ObjectAlloc
- (id)retain {
    return _objc_rootRetain(self);
}


+ (BOOL)_tryRetain {
    return YES;
}

// Replaced by ObjectAlloc
- (BOOL)_tryRetain {
    return _objc_rootTryRetain(self);
}

+ (BOOL)_isDeallocating {
    return NO;
}

- (BOOL)_isDeallocating {
    return _objc_rootIsDeallocating(self);
}

+ (BOOL)allowsWeakReference { 
    return YES; 
}

+ (BOOL)retainWeakReference {
    return YES; 
}

- (BOOL)allowsWeakReference { 
    return ! [self _isDeallocating]; 
}

- (BOOL)retainWeakReference { 
    return [self _tryRetain]; 
}

+ (oneway void)release {
}

// Replaced by ObjectAlloc
- (oneway void)release {
    _objc_rootRelease(self);
}

+ (id)autorelease {
    return (id)self;
}

// Replaced by ObjectAlloc
- (id)autorelease {
    return _objc_rootAutorelease(self);
}

+ (NSUInteger)retainCount {
    return ULONG_MAX;
}

- (NSUInteger)retainCount {
    return _objc_rootRetainCount(self);
}

+ (id)alloc {
    return _objc_rootAlloc(self);
}

// Replaced by ObjectAlloc
+ (id)allocWithZone:(struct _NSZone *)zone {
    return _objc_rootAllocWithZone(self, (malloc_zone_t *)zone);
}

// Replaced by CF (throws an NSException)
+ (id)init {
    return (id)self;
}

- (id)init {
    return _objc_rootInit(self);
}

// Replaced by CF (throws an NSException)
+ (void)dealloc {
}


// Replaced by NSZombies
- (void)dealloc {
    _objc_rootDealloc(self);
}

// Previously used by GC. Now a placeholder for binary compatibility.
- (void) finalize {
}

+ (struct _NSZone *)zone {
    return (struct _NSZone *)_objc_rootZone(self);
}

- (struct _NSZone *)zone {
    return (struct _NSZone *)_objc_rootZone(self);
}

+ (id)copy {
    return (id)self;
}

+ (id)copyWithZone:(struct _NSZone *)zone {
    return (id)self;
}

- (id)copy {
    return [(id)self copyWithZone:nil];
}

+ (id)mutableCopy {
    return (id)self;
}

+ (id)mutableCopyWithZone:(struct _NSZone *)zone {
    return (id)self;
}

- (id)mutableCopy {
    return [(id)self mutableCopyWithZone:nil];
}

@end

C++里定义的锁的枚举

//锁的总类
enum class lockkind {
    MUTEX = 1, MONITOR = 2, RDLOCK = 3, WRLOCK = 4, RECURSIVE = 5
};

下面是宏定义

#define MUTEX     lockkind::MUTEX //互斥
#define MONITOR   lockkind::MONITOR //观察
#define RDLOCK    lockkind::RDLOCK //read
#define WRLOCK    lockkind::WRLOCK   //write
#define RECURSIVE lockkind::RECURSIVE//递归

'strncmp'
strncmp函数为字符串比较函数，字符串大小的比较是以ASCII 码表上的顺序来决定，此顺序亦为字符的值。其函数声明为int strncmp ( const char * str1, const char * str2, size_t n );功能是把 str1 和 str2 进行比较，最多比较前 n 个字节，若str1与str2的前n个字符相同，则返回0；若s1大于s2，则返回大于0的值；若s1 小于s2，则返回小于0的值。

strchr函数功能为在一个串中查找给定字符的第一个匹配之处。函数原型为：char *strchr(const char *str, int c)，即在参数 str 所指向的字符串中搜索第一次出现字符 c（一个无符号字符）的位置。