GCD Inside: GCD 数据结构
1 OS_object
OS_object
由下面宏OS_OBJECT_DEC_BASE
扩展而来:
// 1. os/object.h
OS_OBJECT_DECL_BASE(object, NSObject);
// 2. os/object.h
#define OS_OBJECT_DECL_BASE(name, ...) \
@interface OS_OBJECT_CLASS(name) : __VA_ARGS__ \
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift"); \
@end
扩展之后的结果为:
@interface OS_object : NSObject
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift");
@end
从扩展的结果来看,OS_object
继承自NSObject
。
OS_object
实现部分位于 src/object.m 中:
@implementation OS_OBJECT_CLASS(object)
DISPATCH_UNAVAILABLE_INIT()
-(id)retain {
return _os_object_retain(self);
}
-(oneway void)release {
return _os_object_release_without_xref_dispose(self);
}
-(NSUInteger)retainCount {
return _os_object_retain_count(self);
}
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-implementations"
-(BOOL)retainWeakReference {
return _os_object_retain_weak(self);
}
-(BOOL)allowsWeakReference {
return _os_object_allows_weak_reference(self);
}
#pragma clang diagnostic pop
- (void)_xref_dispose {
return _os_object_release_internal(self);
}
@end
宏OS_OBJECT_CLASS
的作用就是给宏参数加一个OS_
前缀,因此OS_OBJECT_CLASS(object)
扩展之后就是OS_object
。
GCD 源码为OS_object
定义了一个指针类型:
// 1. os/object_private.h
typedef OS_OBJECT_CLASS(object) *_os_object_t;
上面代码中将宏扩展开,就是做了如下定义:
typdef OS_object *_os_object_t;
2 OS_dispatch_object
OS_dispatch_object
由宏OS_OBJECT_DECL_CLASS
扩展而来:
// 1. dispatch/object.h
OS_OBJECT_DECL_CLASS(dispatch_object);
// 2. os/object.h
#define OS_OBJECT_DECL_CLASS(name) \
OS_OBJECT_DECL_SUBCLASS_SWIFT(name, object)
// 3. os/object.h
#define OS_OBJECT_DECL_SUBCLASS_SWIFT(name, super) \
OS_EXPORT OS_OBJECT_OBJC_RUNTIME_VISIBLE \
OS_OBJECT_DECL_IMPL_CLASS(name, OS_OBJECT_CLASS(super))
// 4. os/object.h
#define OS_OBJECT_DECL_IMPL_CLASS(name, ...) \
OS_OBJECT_DECL_BASE(name, ## __VA_ARGS__) \
typedef OS_OBJECT_CLASS(name) \
* OS_OBJC_INDEPENDENT_CLASS name##_t
扩展之后的结果为:
@interface OS_dispatch_object : OS_object
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift");
@end
typedef OS_dispatch_object *dispatch_object_t
从扩展结果看,OS_dispatch_object
继承自OS_object
。
上面注释 3 处的宏OS_OBJECT_OBJC_RUNTIME_VISIBLE
和注释 4 处的宏OS_OBJC_INDEPENDENT_CLASS
都是 Clang 编译器的属性,对数据结构本身没有影响,因此没有写出来。比如宏OS_OBJECT_OBJC_RUNTIME_VISIBLE
扩展之后就是:
__attribute__((objc_runtime_visible))
OS_dispatch_object
的实现位于 src/object.m 中:
@implementation DISPATCH_CLASS(object)
DISPATCH_UNAVAILABLE_INIT()
- (NSString *)debugDescription {
Class nsstring = objc_lookUpClass("NSString");
if (!nsstring) return nil;
char buf[2048];
struct dispatch_object_s *obj = (struct dispatch_object_s *)self;
if (dx_vtable(obj)->do_debug) {
dx_debug(obj, buf, sizeof(buf));
} else {
strlcpy(buf, object_getClassName(self), sizeof(buf));
}
NSString *format = [nsstring stringWithUTF8String:"<%s: %s>"];
if (!format) return nil;
return [nsstring stringWithFormat:format, object_getClassName(self), buf];
}
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wobjc-missing-super-calls"
- (void)dealloc {
return _dispatch_dispose(self);
}
#pragma clang diagnostic pop
@end
宏DISPATCH_CLASS
的作用是在宏参数前面加上前缀OS_dispatch_
,因此DISPATCH_CLASS(object)
扩展之后就是OS_dispatch_object
。
3 OS_dispatch_queue
OS_dispatch_queue
由宏DISPATCH_DECL_FACTORY_CLASS_SWIFT
扩展而来:
// 1. dispatch/queue.h
DISPATCH_DECL_FACTORY_CLASS_SWIFT(dispatch_queue, DispatchQueue);
// 2. dispatch/object.h
#define DISPATCH_DECL_FACTORY_CLASS_SWIFT(name, swift_name) \
OS_OBJECT_SWIFT_HAS_MISSING_DESIGNATED_INIT DISPATCH_DECL_SWIFT(name, swift_name)
// 3. dispatch/object.h
#define DISPATCH_DECL_SWIFT(name, swift_name) DISPATCH_SWIFT_NAME(swift_name) DISPATCH_DECL(name)
// 4. dispatch/object.h
#define DISPATCH_DECL(name) OS_OBJECT_DECL_SENDABLE_SUBCLASS_SWIFT(name, dispatch_object)
// 5. os/object.h
#define OS_OBJECT_DECL_SENDABLE_SUBCLASS_SWIFT(name, super) \
OS_EXPORT OS_OBJECT_OBJC_RUNTIME_VISIBLE OS_OBJECT_SWIFT_SENDABLE \
OS_OBJECT_DECL_IMPL_CLASS(name, OS_OBJECT_CLASS(super))
扩展之后的结果为:
@interface OS_dispatch_queue : OS_dispatch_object
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift");
@end
typedef OS_dispatch_queue *dispatch_queue_t;
从扩展结果看OS_dispatch_queue
继承自OS_dispatch_object
。
OS_dispatch_queue
的实现部分位于 src/object.m 中:
@implementation DISPATCH_CLASS(queue)
OS_OBJECT_NONLAZY_CLASS_LOAD
DISPATCH_UNAVAILABLE_INIT()
DISPATCH_OBJECT_USES_XREF_DISPOSE()
- (NSString *)description {
Class nsstring = objc_lookUpClass("NSString");
if (!nsstring) return nil;
NSString *format = [nsstring stringWithUTF8String:"<%s: %s>"];
if (!format) return nil;
return [nsstring stringWithFormat:format, object_getClassName(self),
dispatch_queue_get_label(self), self];
}
- (void)_xref_dispose {
_dispatch_queue_xref_dispose((struct dispatch_queue_s *)self);
[super _xref_dispose];
}
@end
宏DISPATCH_CLASS(queue)
扩展之后就是OS_dispatch_queue
。
4 OS_dispatch_queue_serial
OS_dispatch_queue_serial
由宏DISPATCH_DECL_SERIAL_EXECUTOR_SWIFT
扩展而来:
// 1. dispatch/queue.h
DISPATCH_DECL_SERIAL_EXECUTOR_SWIFT(dispatch_queue_serial, DispatchSerialQueue);
// 2. dispatch/object.h
#define DISPATCH_DECL_SERIAL_EXECUTOR_SWIFT(name, swift_name) \
DISPATCH_DECL_SUBCLASS_SWIFT(name, dispatch_queue, swift_name)
// 3. dispatch/object.h
#define DISPATCH_DECL_SUBCLASS_SWIFT(name, base, swift_name) \
DISPATCH_SWIFT_NAME(swift_name) DISPATCH_DECL_SUBCLASS(name, base)
// 4. dispatch/object.h
#define DISPATCH_DECL_SUBCLASS(name, base) OS_OBJECT_DECL_SENDABLE_SUBCLASS_SWIFT(name, base)
扩展之后的结果为:
@interface OS_dispatch_queue_serial : OS_dispatch_queue
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift");
@end
typedef OS_dispatch_queue_searial *dispatch_queue_searial_t;
从扩展结果看,OS_dispatch_queue_serial
继承自OS_dispatch_queue
。
OS_dispatch_queue_serial
的实现位于 src/object.m 中:
// 1. src/object.m
DISPATCH_CLASS_IMPL(queue_serial)
// 2. src/object.m
#define DISPATCH_CLASS_IMPL(name) \
EMPTY_OS_OBJECT_CLASS_IMPL(DISPATCH_CLASS(name))
// 3. src/object.m
#define EMPTY_OS_OBJECT_CLASS_IMPL(name) \
OS_OBJECT_NONLAZY_CLASS \
@implementation name \
OS_OBJECT_NONLAZY_CLASS_LOAD \
DISPATCH_UNAVAILABLE_INIT() \
@end
// 4. src/object_internal.h
#define DISPATCH_UNAVAILABLE_INIT() \
- (instancetype)init { \
DISPATCH_CLIENT_CRASH(0, "-init called directly"); \
return [super init]; \
}
扩展之后的结果为:
@implementation OS_dispatch_queue_serial
- (instancetype)init {
return [super init];
}
@end
5 OS_dispatch_queue_concurrent
OS_dispatch_queque_concurrent
由宏DISPATCH_DECL_SUBCLASS_SWIFT
扩展而来:
// 1. dispatch/queue.h
DISPATCH_DECL_SUBCLASS_SWIFT(dispatch_queue_concurrent, dispatch_queue, DispatchConcurrentQueue);
扩展结果为:
@interface OS_dispatch_queue_concurrent : OS_dispatch_queue
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift");
@end
typedef OS_dispatch_queue_concurrent *dispatch_queue_concurrent_t;
从扩展结果看,OS_dispatch_queue_concurrent
继承自OS_dispatch_queue
。
OS_dispatch_queue_concurrent
的实现位于 src/object.m 中:
DISPATCH_CLASS_IMPL(queue_concurrent)
扩展之后的结果为:
@implementation OS_dispatch_queue_concurrent
- (instancetype)init {
return [super init];
}
@end
5 OS_dispatch_queue_main
OS_dispatch_queue_main
由宏DISPATCH_DECL_SUBCLASS
扩展而来:
// 1. dispatch/queue.h
DISPATCH_DECL_SUBCLASS(dispatch_queue_main, dispatch_queue_serial);
扩展的结果为:
@interface OS_dispatch_queue_main : OS_dispatch_queue_serial
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift");
@end
typedef OS_dispatch_queue_main *dispatch_queue_main_t;
从扩展结果看,OS_dispatch_queue_main
继承自OS_dispatch_queue_serial
。
OS_dispatch_queue_main
的实现部分位于 src/object.m 中:
// 1. src/object.m
DISPATCH_CLASS_IMPL(queue_main)
扩展之后的结果为:
@implementation OS_dispatch_queue_main
- (instancetype)init {
return [super init];
}
@end
6 OS_dispatch_queue_global
OS_disaptch_queue_global
由宏DISPATCH_DECL_SUBCLASS
扩展而来:
// 1. dispatch/queue.h
DISPATCH_DECL_SUBCLASS(dispatch_queue_global, dispatch_queue);
扩展之后的结果为:
@interface OS_dispatch_queue_global : OS_dispatch_queue
- (instancetype)init OS_SWIFT_UNAVAILABLE("Unavailable in Swift");
@end
typedef OS_dispatch_queue_global *dispatch_queue_global_t;
从扩展结果看,OS_dispatch_queue_global
继承自OS_dispatch_queue
。
OS_dispatch_queue_global
的实现位于 src/object.m 中:
// 1. src/object.m
DISPATCH_CLASS_IMPL(queue_global)
扩展结果之后为:
@implementation OS_dispatch_queue_global
- (instancetype)init {
return [super init];
}
@end
2 OC 协议
2.1 <OS_object>
<OS_object>
由宏OS_OBJECT_DECL_PROTOCOL
定义:
// 1. os/object_private.h
OS_OBJECT_DECL_PROTOCOL(object, <NSObject>);
// 2. os/object.h
#define OS_OBJECT_DECL_PROTOCOL(name, ...) \
@protocol OS_OBJECT_CLASS(name) __VA_ARGS__ \
@end
宏扩展的结果为:
@protocol OS_object <NSObject>
@end
从扩展结果可以知道,<OS_object>
继承自<NSObject>
。
2.2 <OS_dispatch_object>
<OS_dispatch_object>
由宏_OS_OBJECT_DECL_PROTOCOL
定义:
// 1. src/object_internal.h
_OS_OBJECT_DECL_PROTOCOL(dispatch_object, object);
// 2. os/object_private.h
#define _OS_OBJECT_DECL_PROTOCOL(name, super) \
OS_OBJECT_DECL_PROTOCOL(name, <OS_OBJECT_CLASS(super)>)
宏扩展之后的结果为:
@protocol OS_dispatch_object <OS_object>
@end
从扩展结果可以看出,<OS_dispatch_object>
继承自<OS_object>
。
2.3 <OS_dispatch_queue>
<OS_dispatch_queue>
由宏DISPATCH_CLASS_DECL
定义:
// 1. src/queue_internal.h
DISPATCH_CLASS_DECL(queue, QUEUE);
// 2. src/object_internal.h
#define DISPATCH_CLASS_DECL(name, cluster) \
_OS_OBJECT_DECL_PROTOCOL(dispatch_##name, dispatch_object) \
_OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL(dispatch_##name, dispatch_##name) \
DISPATCH_CLASS_DECL_BARE(name, cluster)
宏DISPATCH_CLASS_DECL
有 3 个宏构成,其中宏DISPATCH_CLASS_DECL_BARE
后面再说。
宏_OS_OBJECT_DECL_PROTOCOL
扩展之后的结果为:
@protocol OS_dispatch_queue <OS_dispatch_object>
@end
从扩展结果看,<OS_dispatch_queue>
继承自<OS_dispatch_object>
。
宏_OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL
的定义如下:
// 1. os/object_private.h
#define _OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL(name, super) \
OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL(name, super)
// 2. os/object.h
#define OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL(name, proto) \
OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL_IMPL( \
OS_OBJECT_CLASS(name), OS_OBJECT_CLASS(proto))
// 3. os/object.h
#define OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL_IMPL(name, proto) \
@interface name () <proto> \
@end
宏的扩展结果为:
@interface OS_dispatch_queue () <OS_dispatch_queue>
@end
从扩展结果可知,OS_dispatch_queue
实现了同名协议<OS_dispatch_queue>
。
2.4 <OS_dispatch_queue_serial>
<OS_dispatch_queue_serial>
由宏DISPATCH_SUBCLASS_DECL
定义:
// 1. src/queue_internal.h
DISPATCH_SUBCLASS_DECL(queue_serial, queue_serial_executor, lane);
// 2. src/object_internal.h
#define DISPATCH_SUBCLASS_DECL(name, super, ctype) \
_OS_OBJECT_DECL_PROTOCOL(dispatch_##name, dispatch_##super); \
_OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL(dispatch_##name, dispatch_##name) \
OS_OBJECT_SUBCLASS_DECL(dispatch_##name, dispatch_##ctype)
宏DISPATCH_SUBCLASS_DECL
由 3 个宏构成,其中宏OS_OBJECT_SUBCLASS_DECL
后面再说。
宏_OS_OBJECT_DECL_PROTOCOL
_OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL
扩展的结果为:
@protocol OS_dispatch_queue_serial <OS_dispatch_queue_serial_executor>
@end
@interface OS_dispatch_queue_serial () <OS_dispatch_queue_serial>
@end
从扩展结果可以知道,<OS_dispatch_queue_serial>
继承自<OS_dispatch_queue_serial_executor>
。同时,OS_dispatch_queue_serial
实现了同名协议<OS_dispatch_queue_serial>
。
协议<OS_dispatch_queue_serial_executor>
是 GCD 内部的一个协议,同样也有宏DISPATCH_SUBCLASS_DECL
定义:
// 1. src/queue_internal.h
DISPATCH_SUBCLASS_DECL(queue_serial_executor, queue, lane);
因此,协议<OS_dispatch_queue_serial_executor>继承自
<OS_dispatch_queue>`。
2.5 <OS_dispatch_queue_concurrent>
<OS_dispatch_queue_concurrent>
由宏DISPATCH_SUBCLASS_DECL
定义:
// 1. src/queue_internal.h
DISPATCH_SUBCLASS_DECL(queue_concurrent, queue, lane);
宏扩展的结果为:
@protocol OS_dispatch_queue_concurrent <OS_dispatch_queue>
@end
@interface OS_dispatch_queue_concurrent () <OS_dispatch_queue_concurrent>
@end
从扩展结果可以知道,<OS_dispatch_queue_concurrent>
继承自<OS_dispatch_queue>
。同时,OS_dispatch_queue_concurrent
实现了同名的<OS_dispatch_queue_concurrent>
。
2.6 <OS_dispatch_queue_main>
OS_dispatch_queue_main
由宏DISPATCH_SUBCLASS_DECL
定义:
// 1. src/queue_internal.h
DISPATCH_SUBCLASS_DECL(queue_main, queue_serial, lane);
宏扩展结果为:
@protocol OS_dispatch_queue_main <OS_dispatch_queue_serial>
@end
@interface OS_dispatch_queue_main () <OS_dispatch_queue_main>
@end
从扩展结果可以知道,<OS_dispatch_queue_main>
继承自<OS_dispatch_queue_serial>
。同时,OS_dispatch_queue_main
实现了同名的<OS_dispatch_queue_main>
。
2.7 <OS_dispatch_queue_global>
<OS_dispatch_queue_global>
由宏DISPATCH_SUBCLASS_DECL`定义:
// 1. src/queue_internal.h
DISPATCH_SUBCLASS_DECL(queue_global, queue, lane);
宏扩展的结果为:
@protocol OS_disaptch_queue_global <OS_dispatch_queue>
@end
@interface OS_dispatch_queue_global () <OS_dispatch_queue_global>
@end
从扩展结果可以知道,<OS_dispatch_queue_global>
继承自<OS_dispatch_queue>
。同时,OS_dispatch_queue_global
实现了同名协议<OS_dispatch_queue_global>
。
3 Struct
3.1 _os_object_s 与 _os_object_vtable_s
_os_object_s
定义如下:
// 1. src/object_internal.h
typedef struct _os_object_s {
_OS_OBJECT_HEADER(
const _os_object_vtable_s *__ptrauth_objc_isa_pointer os_obj_isa,
os_obj_ref_cnt,
os_obj_xref_cnt);
} _os_object_s;
宏_OS_OBJECT_HEADER
定义如下:
// 1. os/object_private.h
#define _OS_OBJECT_HEADER(isa, ref_cnt, xref_cnt) \
isa; /* must be pointer-sized and use __ptrauth_objc_isa_pointer */ \
int volatile ref_cnt; \
int volatile xref_cnt
因此,_os_object_s
完整的定义如下:
typedef struct _os_object_s {
const _os_object_vtable_s *__ptrauth_objc_isa_pointer os_obj_isa,
int volatile os_obj_ref_cnt;
int volatile os_obj_xref_cnt;
} _os_object_s;
_os_object_vtable_s
的定义如下:
// 1. src/object_internal.h
typedef struct _os_object_vtable_s {
_OS_OBJECT_CLASS_HEADER();
} _os_object_vtable_s;
宏_OS_OBJECT_CLASS_HEADER
定义如下:
// 1. os/object_private.h
// Must match size of compiler-generated OBJC_CLASS structure rdar://10640168
#define _OS_OBJECT_CLASS_HEADER() \
void *_os_obj_objc_class_t[5]
因此,_os_object_vtalbe_s
的完整定义为:
typedef struct _os_object_vtable_s {
void *_os_obj_objc_class_t[5];
} _os_object_vtable_s;
3.2 dispatch_object_s 与 dispatch_object_vtable_s
dispatch_object_s
定义如下:
// 1. src/object_internal.h
struct dispatch_object_s {
_DISPATCH_OBJECT_HEADER(object);
};
宏_DISPATCH_OBJECT_HEADER
的定义如下:
// 1. src/object_internal.h
#define _DISPATCH_OBJECT_HEADER(x) \
_DISPATCH_OBJECT_HEADER_INTERNAL(x) \
struct dispatch_queue_s *do_targetq; \
void *do_ctxt; \
union { \
dispatch_function_t DISPATCH_FUNCTION_POINTER do_finalizer; \
void *do_introspection_ctxt; \
}
// 2. src/object_internal.h
#define _DISPATCH_OBJECT_HEADER(x) \
_DISPATCH_OBJECT_HEADER_INTERNAL(x) \
struct dispatch_queue_s *do_targetq; \
void *do_ctxt; \
union { \
dispatch_function_t DISPATCH_FUNCTION_POINTER do_finalizer; \
void *do_introspection_ctxt; \
}
// 3. src/object_internal.h
#define _DISPATCH_OBJECT_HEADER_INTERNAL(x) \
struct _os_object_s _as_os_obj[0]; \
OS_OBJECT_STRUCT_HEADER(dispatch_##x); \
struct dispatch_##x##_s *volatile do_next;
// 4. src/object_internal.h
#define OS_OBJECT_STRUCT_HEADER(x) \
_OS_OBJECT_HEADER(\
const struct x##_vtable_s *__ptrauth_objc_isa_pointer do_vtable, \
do_ref_cnt, \
do_xref_cnt)
因此,dispatch_object_s
展开的完整结果为:
struct dispatch_object_s {
// 这里就是 _os_object_s 内容
const struct dispatch_object_vtable_s *__ptrauth_objc_isa_pointer do_vtable,
int volatile do_ref_cnt;
int volatile do_xref_cnt;
struct dispatch_object_s *volatile do_next;
struct dispatch_queue_s *do_targetq;
void *do_ctx;
union {
dispatch_function_t DISPATCH_FUNCTION_POINTER do_finalizer;
void *do_introspection_ctxt;
}
};
从展开的结果可以看到,dispatch_object_s
的头部区域就是_os_object_s
的内容,可以认为,dispatch_object_s
"继承"自_os_object_s
。
dispatch_object_vtable_s
由宏DISPATCH_CLASS_DECL_BARE
定义:
// 1. src/object_internal.h
DISPATCH_CLASS_DECL_BARE(object, OBJECT);
DISPATCH_CLASS_DECL_BARE
正是组成DISPATCH_CLASS_DECL
的第 3 个宏。
DISPATCH_CLASS_DECL_BARE
的定义如下:
// 1. src/object_internal.h
#define DISPATCH_CLASS_DECL_BARE(name, cluster) \
OS_OBJECT_CLASS_DECL(dispatch_##name, \
DISPATCH_##cluster##_VTABLE_HEADER(dispatch_##name))
因此,宏DISPATCH_CLASS_DECL_BARE(name, OBJECT)
扩展为:
OS_OBJECT_CLASS_DECL(dispatch_object, DISPATCH_OBJECT_VTALBE_HEADER(dispatch_object))
宏DISPATCH_OBJECT_VTABLE_HEADER
的定义如下:
// 1. src/object_internal.h
#define DISPATCH_OBJECT_VTABLE_HEADER(x) \
unsigned long const do_type; \
void DISPATCH_VTABLE_ENTRY(do_dispose)(struct x##_s *, \
bool *allow_free); \
size_t DISPATCH_VTABLE_ENTRY(do_debug)(struct x##_s *, \
char *, size_t); \
void DISPATCH_VTABLE_ENTRY(do_invoke)(struct x##_s *, \
dispatch_invoke_context_t, dispatch_invoke_flags_t)
// 2. src/internal.h
#define DISPATCH_VTABLE_ENTRY(op) \
(* __ptrauth(ptrauth_key_process_independent_code, true, \
ptrauth_string_discriminator("dispatch." #op)) const op)
宏DISPATCH_VTALBE_ENTRY
中的__ptrauth
与PAC
指针认证有关,与 GCD 功能无关,扩展结果中可以剔除这些扩展,因此宏DISPATCH_OBJECT_VTABLE_HEADER
的扩展结果为:
unsigned const do_type;
void (* const do_dispose)(struct dispatch_object_s *, bool *allow_free);
size_t (* const do_debug)(struct dispatch_object_s *, char *, size_t);
void (* const do_invoke)(struct dispatch_object_s *, dispatch_invoke_context_t, dispatch_invoke_flags_t);
宏OS_OBJECT_CLASS_DECL
的定义如下:
// 1. src/object_internal.h
#define OS_OBJECT_CLASS_DECL(name, ...) \
struct name##_s; \
struct name##_extra_vtable_s { \
__VA_ARGS__; \
}; \
struct name##_vtable_s { \
_OS_OBJECT_CLASS_HEADER(); \
struct name##_extra_vtable_s _os_obj_vtable; \
}; \
OS_OBJECT_EXTRA_VTABLE_DECL(name, name) \
extern const struct name##_vtable_s OS_OBJECT_CLASS_SYMBOL(name) \
__asm__(OS_OBJC_CLASS_RAW_SYMBOL_NAME(OS_OBJECT_CLASS(name)))
// 2. os/object_private.h
#define OS_OBJECT_CLASS_SYMBOL(name) OS_##name##_class
// 3. os/object_private.h
#define OS_OBJC_CLASS_RAW_SYMBOL_NAME(name) "_OBJC_CLASS_$_" OS_STRINGIFY(name)
上面代码中__VA_ARGS__
就是宏DISPATCH_OBJECT_VTABLE_HEADER(dispatch_object)
扩展的结果。因此宏DISPATCH_CLASS_DECL_BARE(object, OBJECT)
扩展之后的结果为:
struct dispatch_object_s;
struct dispatch_object_extra_vtable_s {
unsigned const do_type;
void (* const do_dispose)(struct dispatch_object_s *, bool *allow_free);
size_t (* const do_debug)(struct dispatch_object_s *, char *, size_t);
void (* const do_invoke)(struct dispatch_object_s *, dispatch_invoke_context_t, dispatch_invoke_flags_t);
};
struct dispatch_object_vtable_s {
void *_os_obj_objc_class_t[5];
struct dispatch_object_extra_vtable_s _os_obj_vtable;
};
extern const struct dispatch_object_vtable_s OS_dispatch_object_class __asm__("_OBJC_CLASS_$_OS_dispatch_object");
3.3 dispatch_queue_s 与 dispatch_queue_vtable_s
dispatch_queue_s
的定义如下:
// 1. src/queue_internal.h
struct dispatch_queue_s {
DISPATCH_QUEUE_CLASS_HEADER(queue, void *__dq_opaque1);
/* 32bit hole on LP64 */
} DISPATCH_ATOMIC64_ALIGN;
// 2. src/queue_internal.h
#define DISPATCH_QUEUE_CLASS_HEADER(x, __pointer_sized_field__) \
_DISPATCH_QUEUE_CLASS_HEADER(x, __pointer_sized_field__); \
/* LP64 global queue cacheline boundary */ \
unsigned long dq_serialnum; \
const char *dq_label; \
DISPATCH_UNION_LE(uint32_t volatile dq_atomic_flags, \
const uint16_t dq_width, \
const uint16_t __dq_opaque2 \
); \
dispatch_priority_t dq_priority; \
union { \
struct dispatch_queue_specific_head_s *dq_specific_head; \
struct dispatch_source_refs_s *ds_refs; \
struct dispatch_timer_source_refs_s *ds_timer_refs; \
struct dispatch_mach_recv_refs_s *dm_recv_refs; \
struct dispatch_channel_callbacks_s const *dch_callbacks; \
}; \
int volatile dq_sref_cnt
// 3. src/queue_internal.h
#define _DISPATCH_QUEUE_CLASS_HEADER(x, __pointer_sized_field__) \
DISPATCH_OBJECT_HEADER(x); \
__pointer_sized_field__; \
DISPATCH_UNION_LE(uint64_t volatile dq_state, \
dispatch_lock dq_state_lock, \
uint32_t dq_state_bits \
)
// 4. src/object_internal.h
#define DISPATCH_OBJECT_HEADER(x) \
struct dispatch_object_s _as_do[0]; \
_DISPATCH_OBJECT_HEADER(x)
dispatch_queue_s
完整的扩展结果如下:
struct disaptch_queue_s {
// 头部 dispatch_object_s 内容
const struct dispatch_queue_vtable_s *__ptrauth_objc_isa_pointer do_vtable,
int volatile do_ref_cnt;
int volatile do_xref_cnt;
struct dispatch_queue_s *volatile do_next;
struct dispatch_queue_s *do_targetq;
void *do_ctx;
union {
dispatch_function_t DISPATCH_FUNCTION_POINTER do_finalizer;
void *do_introspection_ctxt;
};
void *__dq_opaque1;
union {
uint64_t volatile dq_state;
struct {
dispatch_lock dq_state_lock;
uint32_t dq_state_bits;
};
};
/* LP64 global queue cacheline boundary */
unsigned long dq_serialnum;
const char *dq_label;
union {
uint32_t volatile dq_atomic_flags;
struct {
const uint16_t dq_width;
const uint16_t __dq_opaque2;
};
};
dispatch_priority_t dq_priority;
union {
struct dispatch_queue_specific_head_s *dq_specific_head;
struct dispatch_source_refs_s *ds_refs;
struct dispatch_timer_source_refs_s *ds_timer_refs;
struct dispatch_mach_recv_refs_s *dm_recv_refs;
struct dispatch_channel_callbacks_s const *dch_callbacks;
};
int volatile dq_sref_cnt
}
disaptch_queue_vtable_s
由宏DISPATCH_CLASS_DECL
定义:
// 1. src/queue_internal.h
DISPATCH_CLASS_DECL(queue, QUEUE);
// 2. src/object_internal.h
#define DISPATCH_CLASS_DECL(name, cluster) \
_OS_OBJECT_DECL_PROTOCOL(dispatch_##name, dispatch_object) \
_OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL(dispatch_##name, dispatch_##name) \
DISPATCH_CLASS_DECL_BARE(name, cluster)
具体的说,是构成DISPATCH_CLASS_DECL
宏的第 3 个宏DISPATCH_CLASS_BARE
定义了dispatch_queue_vtable_s
,完整的扩展结果为:
struct dispatch_queue_s;
struct dispatch_queue_extra_vtable_s {
unsigned long const do_type;
void (* const do_dispose)(struct dispatch_queue_s *, bool *allow_free);
size_t (* const do_debug)(struct dispatch_queue_s *, char *, size_t);
void (* const do_invoke)(struct dispatch_queue_s *, dispatch_invoke_context_t, dispatch_qos_t);
void (* const dq_activate)(dispatch_queue_class_t);
void (* const dq_wakeup)(dispatch_queue_class_t, dispatch_qos_t, dispatch_wakeup_flags_t);
void (* const dq_push)(dispatch_queue_class_t, dispatch_object_t, dispatch_qos_t);
};
struct dispatch_queue_vtable_s {
void *_os_obj_objc_class_t[5];
struct dispatch_queue_extra_vtable_s _os_obj_vtable;
}
extern const struct dispatch_queue_vtable_s OS_dispatch_queue_class __asm__("_OBJC_CLASS_$_OS_dispatch_queue");
3.4 dispatch_lane_s 与 dispatch_lane_vtable_s
dispatch_lane_s
的定义如下:
// 1. src/queue_internal.h
typedef struct dispatch_lane_s {
DISPATCH_LANE_CLASS_HEADER(lane);
/* 32bit hole on LP64 */
} DISPATCH_ATOMIC64_ALIGN *dispatch_lane_t;
// 2. src/queue_internal.h
#define DISPATCH_LANE_CLASS_HEADER(x) \
struct dispatch_queue_s _as_dq[0]; \
DISPATCH_QUEUE_CLASS_HEADER(x, \
struct dispatch_object_s *volatile dq_items_tail); \
dispatch_unfair_lock_s dq_sidelock; \
struct dispatch_object_s *volatile dq_items_head; \
uint32_t dq_side_suspend_cnt
扩展之后的完整结果为:
typedef struct dispatch_lane_s {
// 这里是 dispatch_queue_s
const struct dispatch_lane_vtable_s *__ptrauth_objc_isa_pointer do_vtable;
int volatile do_ref_cnt;
int volatile do_xref_cnt;
struct dispatch_lane_s *volatile do_next;
struct dispatch_queue_s *do_targetq;
void *do_ctxt;
union {
dispatch_function_t DISPATCH_FUNCTION_POINTER do_finalizer;
void *do_introspection_ctxt;
};
struct dispatch_object_s *volatile dq_items_tail;
union {
uint64_t volatile dq_state;
struct {
dispatch_lock dq_state_lock;
uint32_t dq_state_bits;
};
);
/* LP64 global queue cacheline boundary */ \
unsigned long dq_serialnum; \
const char *dq_label; \
union {
uint32_t volatile dq_atomic_flags;
struct {
const uint16_t dq_width;
const uint16_t __dq_opaque2;
};
);
dispatch_priority_t dq_priority;
union {
struct dispatch_queue_specific_head_s *dq_specific_head;
struct dispatch_source_refs_s *ds_refs;
struct dispatch_timer_source_refs_s *ds_timer_refs;
struct dispatch_mach_recv_refs_s *dm_recv_refs;
struct dispatch_channel_callbacks_s const *dch_callbacks;
};
int volatile dq_sref_cnt;
dispatch_unfair_lock_s dq_sidelock;
struct dispatch_object_s *volatile dq_items_head;
uint32_t dq_side_suspend_cnt;
} *dispatch_lane_t;
dispatch_lane_vtable_s
由宏DISPATCH_CLASS_DECL_BARE
定义:
// 1. src/queue_internal.h
DISPATCH_CLASS_DECL_BARE(lane, QUEUE);
dispatch_lane_vtable_s
由宏OS_OBJECT_SUBCLASS_DECL
定义,完整的展开结果为:
struct dispatch_lane_s;
struct dispatch_lane_extra_vtable_s {
unsigned long const do_type;
void (* const do_dispose)(struct dispatch_lane_s * bool *allow_free);
size_t (* const do_debug)(struct dispatch_lane_s *, char *, size_t);
void (* const do_invoke)(struct dispatch_lane_s * dispatch_invoke_context_t, dispatch_invoke_flags_t);
void (* const dq_activate)(dispatch_queue_class_t);
void (* const dq_wakeup)(dispatch_queue_class_t, dispatch_qos_t, dispatch_wakeup_flags_t);
void (* const dq_push)(dispatch_queue_class_t, dispatch_object_t, dispatch_qos_t);
}
struct dispatch_lane_vtable_s {
void *_os_obj_objc_class_t[5];
struct dispatch_lane_extra_vtable_s _os_obj_vtable;
}
extern const struct dispatch_lane_vtable_s OS_dispatch_lane_class __asm__("_OBJC_CLASS_$_OS_dispatch_lane")
与dispatch_lane_vtable_s
有关的 3 个宏定义如下:
// 1. src/queue_internal.h
DISPATCH_SUBCLASS_DECL(queue_serial, queue_serial_executor, lane);
DISPATCH_SUBCLASS_DECL(queue_main, queue_serial, lane);
DISPATCH_SUBCLASS_DECL(queue_concurrent, queue, lane);
DISPATCH_SUBCLASS_DECL(queue_global, queue, lane);
// 2. src/object_internal.h
#define DISPATCH_SUBCLASS_DECL(name, super, ctype) \
_OS_OBJECT_DECL_PROTOCOL(dispatch_##name, dispatch_##super); \
_OS_OBJECT_CLASS_IMPLEMENTS_PROTOCOL(dispatch_##name, dispatch_##name) \
OS_OBJECT_SUBCLASS_DECL(dispatch_##name, dispatch_##ctype)
// 3. src/object_internal.h
// define a new subclass used in a cluster
#define OS_OBJECT_SUBCLASS_DECL(name, ctype) \
struct name##_s; \
OS_OBJECT_EXTRA_VTABLE_DECL(name, ctype) \
extern const struct ctype##_vtable_s OS_OBJECT_CLASS_SYMBOL(name) \
__asm__(OS_OBJC_CLASS_RAW_SYMBOL_NAME(OS_OBJECT_CLASS(name)))
之前在第 2 部分没有介绍宏OS_OBJECT_SUBCLASS_DECL
,这里继续介绍。
代码注释 1 处 4 个宏展开之后的结果为:
struct dispatch_queue_serial_s;
extern const struct dispatch_lane_vtable_s OS_dispatch_queue_serial_class __asm__("_OBJC_CLASS_$_OS_dispatch_queue_serial");
struct dispatch_queue_main_s;
extern const struct dispatch_lane_vtable_s OS_dispatch_queue_main_class __asm__("_OBJC_CLASS_$_OS_dispatch_queue_main");
struct dispatch_queue_concurrent_s;
extern const struct dispatch_lane_vtable_s OS_dispatch_queue_concurrent_class __asm__("_OBJC_CLASS_$_OS_dispatch_concurrent");
struct dispatch_queue_global_s;
extern const struct dispatch_lane_vtable_s OS_dispatch_queue_global_class __asm__("_OBJC_CLASS_$_OS_dispatch_queue_global");
## 3.6 dispatch_queue_global_s
`dispatch_queue_global_s`定义如下:
```c++
// 1. src/queue_internal.h
struct dispatch_queue_global_s {
DISPATCH_QUEUE_ROOT_CLASS_HEADER(lane);
} DISPATCH_CACHELINE_ALIGN;
// 2. src/queue_internal.h
#define DISPATCH_QUEUE_ROOT_CLASS_HEADER(x) \
struct dispatch_queue_s _as_dq[0]; \
DISPATCH_QUEUE_CLASS_HEADER(x, \
struct dispatch_object_s *volatile dq_items_tail); \
int volatile dgq_thread_pool_size; \
struct dispatch_object_s *volatile dq_items_head; \
int volatile dgq_pending;
完整扩展结果如下:
typedef struct dispatch_queue_global_s {
// 这里是 dispatch_queue_s
const struct dispatch_lane_vtable_s *__ptrauth_objc_isa_pointer do_vtable;
int volatile do_ref_cnt;
int volatile do_xref_cnt;
struct dispatch_lane_s *volatile do_next;
struct dispatch_queue_s *do_targetq;
void *do_ctxt;
union {
dispatch_function_t DISPATCH_FUNCTION_POINTER do_finalizer;
void *do_introspection_ctxt;
};
struct dispatch_object_s *volatile dq_items_tail;
union {
uint64_t volatile dq_state;
struct {
dispatch_lock dq_state_lock;
uint32_t dq_state_bits;
};
);
/* LP64 global queue cacheline boundary */ \
unsigned long dq_serialnum; \
const char *dq_label; \
union {
uint32_t volatile dq_atomic_flags;
struct {
const uint16_t dq_width;
const uint16_t __dq_opaque2;
};
);
dispatch_priority_t dq_priority;
union {
struct dispatch_queue_specific_head_s *dq_specific_head;
struct dispatch_source_refs_s *ds_refs;
struct dispatch_timer_source_refs_s *ds_timer_refs;
struct dispatch_mach_recv_refs_s *dm_recv_refs;
struct dispatch_channel_callbacks_s const *dch_callbacks;
};
int volatile dq_sref_cnt;
int volatile dgq_thread_pool_size;
struct dispatch_object_s *volatile dq_items_head;
int volatile dgq_pending;
}
3.7 dispatch_queue_class_t
dispatch_queue_class_t
的定义如下:
// 1. src/internal.h
// Dispatch queue cluster class: type for any dispatch_queue_t
typedef union {
struct dispatch_queue_s *_dq;
struct dispatch_workloop_s *_dwl;
struct dispatch_lane_s *_dl;
struct dispatch_queue_static_s *_dsq;
struct dispatch_queue_global_s *_dgq;
struct dispatch_queue_pthread_root_s *_dpq;
struct dispatch_source_s *_ds;
struct dispatch_channel_s *_dch;
struct dispatch_mach_s *_dm;
dispatch_lane_class_t _dlu;
#ifdef __OBJC__
id<OS_dispatch_queue> _objc_dq;
#endif
} dispatch_queue_class_t DISPATCH_TRANSPARENT_UNION;