objc-internal.h

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此文件包含Objective-C的内部实现细节，适用于特定系统框架的私有接口，包括实例构造、类初始化、内存管理等关键操作。注意，其中的方法和类仅供内部使用，对外界不可预测且可能在更新中改变。
文档地址:http://www.opensource.apple.com/source/objc4/objc4-493.9/runtime/objc-internal.h
/*
 * Copyright (c) 2009 Apple Inc.  All Rights Reserved.
 * 
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */


#ifndef _OBJC_INTERNAL_H
#define _OBJC_INTERNAL_H

/* 
 * WARNING  DANGER  HAZARD  BEWARE  EEK
 * 
 * Everything in this file is for Apple Internal use only.
 * These will change in arbitrary OS updates and in unpredictable ways.
 * When your program breaks, you get to keep both pieces.
 */

/*
 * objc-internal.h: Private SPI for use by other system frameworks.
 */

#include <objc/objc.h>
#include <Availability.h>
#include <malloc/malloc.h>
#include <dispatch/dispatch.h>

__BEGIN_DECLS

// In-place construction of an Objective-C instance.
OBJC_EXPORT id objc_constructInstance(Class cls, void *bytes) 
    __OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_0)
    OBJC_ARC_UNAVAILABLE;
OBJC_EXPORT void *objc_destructInstance(id obj) 
    __OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_0)
    OBJC_ARC_UNAVAILABLE;

// In-place construction of an Objective-C class.
OBJC_EXPORT Class objc_initializeClassPair(Class superclass_gen, const char *name, Class cls_gen, Class meta_gen) 
    __OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_0);

#if __OBJC2__  &&  __LP64__
// Register a tagged pointer class.
OBJC_EXPORT void _objc_insert_tagged_isa(unsigned char slotNumber, Class isa)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_4_3);
#endif

// Batch object allocation using malloc_zone_batch_malloc().
OBJC_EXPORT unsigned class_createInstances(Class cls, size_t extraBytes, 
                                           id *results, unsigned num_requested)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_4_3)
    OBJC_ARC_UNAVAILABLE;

// Get the isa pointer written into objects just before being freed.
OBJC_EXPORT Class _objc_getFreedObjectClass(void)
    __OSX_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

// Substitute receiver for messages to nil.
// Not supported for all messages to nil.
OBJC_EXPORT id _objc_setNilReceiver(id newNilReceiver)
    __OSX_AVAILABLE_STARTING(__MAC_10_3, __IPHONE_NA);
OBJC_EXPORT id _objc_getNilReceiver(void)
    __OSX_AVAILABLE_STARTING(__MAC_10_3, __IPHONE_NA);

// Return NO if no instance of `cls` has ever owned an associative reference.
OBJC_EXPORT BOOL class_instancesHaveAssociatedObjects(Class cls)
    __OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_0);

// Return YES if GC is on and `object` is a GC allocation.
OBJC_EXPORT BOOL objc_isAuto(id object) 
    __OSX_AVAILABLE_STARTING(__MAC_10_4, __IPHONE_NA);

// env NSObjCMessageLoggingEnabled
OBJC_EXPORT void instrumentObjcMessageSends(BOOL flag)
    __OSX_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

// GC startup callback from Foundation
OBJC_EXPORT malloc_zone_t *objc_collect_init(int (*callback)(void))
    __OSX_AVAILABLE_STARTING(__MAC_10_4, __IPHONE_NA);

// Plainly-implemented GC barriers. Rosetta used to use these.
OBJC_EXPORT id objc_assign_strongCast_generic(id value, id *dest)
    UNAVAILABLE_ATTRIBUTE;
OBJC_EXPORT id objc_assign_global_generic(id value, id *dest)
    UNAVAILABLE_ATTRIBUTE;
OBJC_EXPORT id objc_assign_threadlocal_generic(id value, id *dest)
    UNAVAILABLE_ATTRIBUTE;
OBJC_EXPORT id objc_assign_ivar_generic(id value, id dest, ptrdiff_t offset)
    UNAVAILABLE_ATTRIBUTE;

// Install missing-class callback. Used by the late unlamented ZeroLink.
OBJC_EXPORT void _objc_setClassLoader(BOOL (*newClassLoader)(const char *))  OBJC2_UNAVAILABLE;

// This can go away when AppKit stops calling it (rdar://7811851)
#if __OBJC2__
OBJC_EXPORT void objc_setMultithreaded (BOOL flag)
    __OSX_AVAILABLE_BUT_DEPRECATED(__MAC_10_0,__MAC_10_5, __IPHONE_NA,__IPHONE_NA);
#endif

// Used by ExceptionHandling.framework
#if !__OBJC2__
OBJC_EXPORT void _objc_error(id rcv, const char *fmt, va_list args)
    __attribute__((noreturn))
    __OSX_AVAILABLE_BUT_DEPRECATED(__MAC_10_0,__MAC_10_5, __IPHONE_NA,__IPHONE_NA);

#endif

// External Reference support. Used to support compaction.

enum {
    OBJC_XREF_STRONG = 1,
    OBJC_XREF_WEAK = 2
};
typedef uintptr_t objc_xref_type_t;
typedef uintptr_t objc_xref_t;

OBJC_EXPORT objc_xref_t _object_addExternalReference(id object, objc_xref_type_t type)
     __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_4_3);
OBJC_EXPORT void _object_removeExternalReference(objc_xref_t xref)
     __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_4_3);
OBJC_EXPORT id _object_readExternalReference(objc_xref_t xref)
     __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_4_3);

OBJC_EXPORT uintptr_t _object_getExternalHash(id object)
     __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

// Instance-specific instance variable layout.

OBJC_EXPORT void _class_setIvarLayoutAccessor(Class cls_gen, const uint8_t* (*accessor) (id object))
     __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_NA);
OBJC_EXPORT const uint8_t *_object_getIvarLayout(Class cls_gen, id object)
     __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_NA);

OBJC_EXPORT BOOL _class_usesAutomaticRetainRelease(Class cls)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

// API to only be called by root classes like NSObject or NSProxy

OBJC_EXPORT
id
_objc_rootRetain(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void
_objc_rootRelease(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
bool
_objc_rootReleaseWasZero(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
bool
_objc_rootTryRetain(id obj)
__OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
bool
_objc_rootIsDeallocating(id obj)
__OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
id
_objc_rootAutorelease(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
uintptr_t
_objc_rootRetainCount(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
id
_objc_rootInit(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
id
_objc_rootAllocWithZone(Class cls, malloc_zone_t *zone)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
id
_objc_rootAlloc(Class cls)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void
_objc_rootDealloc(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void
_objc_rootFinalize(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
malloc_zone_t *
_objc_rootZone(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
uintptr_t
_objc_rootHash(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void *
objc_autoreleasePoolPush(void)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void
objc_autoreleasePoolPop(void *context)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);


OBJC_EXPORT id objc_retain(id obj)
    __asm__("_objc_retain")
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT void objc_release(id obj)
    __asm__("_objc_release")
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT id objc_autorelease(id obj)
    __asm__("_objc_autorelease")
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

// wraps objc_autorelease(obj) in a useful way when used with return values
OBJC_EXPORT
id
objc_autoreleaseReturnValue(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

// wraps objc_autorelease(objc_retain(obj)) in a useful way when used with return values
OBJC_EXPORT
id
objc_retainAutoreleaseReturnValue(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

// called ONLY by ARR by callers to undo the autorelease (if possible), otherwise objc_retain
OBJC_EXPORT
id
objc_retainAutoreleasedReturnValue(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void
objc_storeStrong(id *location, id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
id
objc_retainAutorelease(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

// obsolete.
OBJC_EXPORT id objc_retain_autorelease(id obj)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
id
objc_loadWeakRetained(id *location)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
id 
objc_initWeak(id *addr, id val) 
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void 
objc_destroyWeak(id *addr) 
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void 
objc_copyWeak(id *to, id *from)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void 
objc_moveWeak(id *to, id *from) 
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);


OBJC_EXPORT
void
_objc_autoreleasePoolPrint(void)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT BOOL objc_should_deallocate(id object)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT void objc_clear_deallocating(id object)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

 
// to make CF link for now

OBJC_EXPORT
void *
_objc_autoreleasePoolPush(void)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

OBJC_EXPORT
void
_objc_autoreleasePoolPop(void *context)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);



// API to only be called by classes that provide their own reference count storage

OBJC_EXPORT
void
_objc_deallocOnMainThreadHelper(void *context)
    __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_5_0);

#define _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, _dealloc2main)    \
    -(id)retain {                                                       \
        /* this will fail to compile if _rc_ivar is an unsigned type */ \
        int _retain_count_ivar_must_not_be_unsigned[0L - (__typeof__(_rc_ivar))-1] __attribute__((unused)); \
        __typeof__(_rc_ivar) _prev = __sync_fetch_and_add(&_rc_ivar, 2); \
        if (_prev < 0) {                                                \
            __builtin_trap(); /* BUG: retain of dealloc'ed ref */       \
        }                                                               \
        return self;                                                    \
    }                                                                   \
    -(oneway void)release {                                             \
        __typeof__(_rc_ivar) _prev = __sync_fetch_and_sub(&_rc_ivar, 2); \
        if (_prev == 0) {                                               \
            if (__sync_bool_compare_and_swap(&_rc_ivar, -2, 1)) {       \
                if (_dealloc2main) {                                    \
                    dispatch_barrier_async_f(dispatch_get_main_queue(), \
                                             self, _objc_deallocOnMainThreadHelper); \
                } else {                                                \
                    [self dealloc];                                     \
                }                                                       \
            } else {                                                    \
                __builtin_trap(); /* BUG: dangling ref did a retain */  \
            }                                                           \
        } else if (_prev < 0) {                                         \
            __builtin_trap(); /* BUG: over-release */                   \
        }                                                               \
    }                                                                   \
    -(NSUInteger)retainCount {                                          \
        return (_rc_ivar + 2) >> 1;                                     \
    }                                                                   \
    -(BOOL)_tryRetain {                                                   \
        __typeof__(_rc_ivar) _prev;                                     \
        do {                                                            \
            _prev = _rc_ivar;                                           \
            if (_prev & 1) {                                            \
                return 0;                                             \
            } else if (_prev == -2) {                                   \
                return 0;                                             \
            } else if (_prev < -2) {                                    \
                __builtin_trap(); /* BUG: over-release elsewhere */     \
            }                                                           \
        } while ( ! __sync_bool_compare_and_swap(&_rc_ivar, _prev, _prev + 2)); \
        return 1;                                                    \
    }                                                                   \
    -(BOOL)_isDeallocating {                                            \
        if (_rc_ivar == -2) {                                           \
            return 1;                                                   \
        } else if (_rc_ivar < -2) {                                     \
            __builtin_trap(); /* BUG: over-release elsewhere */         \
        }                                                               \
        return _rc_ivar & 1;                                            \
    }

#define _OBJC_SUPPORTED_INLINE_REFCNT(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 0)
#define _OBJC_SUPPORTED_INLINE_REFCNT_WITH_DEALLOC2MAIN(_rc_ivar) _OBJC_SUPPORTED_INLINE_REFCNT_LOGIC(_rc_ivar, 1)

__END_DECLS

#endif