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associate.m
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associate.m
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#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "objc/runtime.h"
#include "objc/objc-arc.h"
#include "nsobject.h"
#include "spinlock.h"
#include "class.h"
#include "dtable.h"
#include "selector.h"
#include "lock.h"
#include "gc_ops.h"
/**
* A single associative reference. Contains the key, value, and association
* policy.
*/
struct reference
{
/**
* The key used for identifying this object. Opaque pointer, should be set
* to 0 when this slot is unused.
*/
void *key;
/**
* The associated object. Note, if the policy is assign then this may be
* some other type of pointer...
*/
void *object;
/**
* Association policy.
*/
uintptr_t policy;
};
#define REFERENCE_LIST_SIZE 10
/**
* Linked list of references associated with an object. We assume that there
* won't be very many, so we don't bother with a proper hash table, and just
* iterate over a list.
*/
struct reference_list
{
/**
* Next group of references. This is only ever used if we have more than
* 10 references associated with an object, which seems highly unlikely.
*/
struct reference_list *next;
/**
* Mutex. Only set for the first reference list in a chain. Used for
* @syncronize().
*/
mutex_t lock;
/**
* Garbage collection type. This stores the location of all of the
* instance variables in the object that may contain pointers.
*/
void *gc_type;
/**
* Array of references.
*/
struct reference list[REFERENCE_LIST_SIZE];
};
enum
{
OBJC_ASSOCIATION_ATOMIC = 0x300,
};
static BOOL isAtomic(uintptr_t policy)
{
return (policy & OBJC_ASSOCIATION_ATOMIC) == OBJC_ASSOCIATION_ATOMIC;
}
static struct reference* findReference(struct reference_list *list, void *key)
{
if (NULL == list) { return NULL; }
for (int i=0 ; i<REFERENCE_LIST_SIZE ; i++)
{
if (list->list[i].key == key)
{
return &list->list[i];
}
}
return NULL;
}
static void cleanupReferenceList(struct reference_list *list)
{
if (NULL == list) { return; }
cleanupReferenceList(list->next);
for (int i=0 ; i<REFERENCE_LIST_SIZE ; i++)
{
struct reference *r = &list->list[i];
if (0 != r->key)
{
r->key = 0;
if (OBJC_ASSOCIATION_ASSIGN != r->policy)
{
// Full barrier - ensure that we've zero'd the key before doing
// this!
__sync_synchronize();
objc_release(r->object);
}
r->object = 0;
r->policy = 0;
}
}
}
static void freeReferenceList(struct reference_list *l)
{
if (NULL == l) { return; }
freeReferenceList(l->next);
gc->free(l);
}
static void setReference(struct reference_list *list,
void *key,
void *obj,
uintptr_t policy)
{
switch (policy)
{
// Ignore any unknown association policies
default: return;
case OBJC_ASSOCIATION_COPY_NONATOMIC:
case OBJC_ASSOCIATION_COPY:
obj = [(id)obj copy];
break;
case OBJC_ASSOCIATION_RETAIN_NONATOMIC:
case OBJC_ASSOCIATION_RETAIN:
obj = objc_retain(obj);
case OBJC_ASSOCIATION_ASSIGN:
break;
}
// While inserting into the list, we need to lock it temporarily.
volatile int *lock = lock_for_pointer(list);
lock_spinlock(lock);
struct reference *r = findReference(list, key);
// If there's an existing reference, then we can update it, otherwise we
// have to install a new one
if (NULL == r)
{
// Search for an unused slot
r = findReference(list, 0);
if (NULL == r)
{
struct reference_list *l = list;
while (NULL != l->next) { l = l->next; }
l->next = gc->malloc(sizeof(struct reference_list));
r = &l->next->list[0];
}
r->key = key;
}
unlock_spinlock(lock);
// Now we only need to lock if the old or new property is atomic
BOOL needLock = isAtomic(r->policy) || isAtomic(policy);
if (needLock)
{
lock = lock_for_pointer(r);
lock_spinlock(lock);
}
r->policy = policy;
id old = r->object;
r->object = obj;
if (OBJC_ASSOCIATION_ASSIGN != r->policy)
{
objc_release(old);
}
if (needLock)
{
unlock_spinlock(lock);
}
}
static void deallocHiddenClass(id obj, SEL _cmd);
static inline Class findHiddenClass(id obj)
{
Class cls = obj->isa;
while (Nil != cls &&
!objc_test_class_flag(cls, objc_class_flag_assoc_class))
{
cls = class_getSuperclass(cls);
}
return cls;
}
static Class allocateHiddenClass(Class superclass)
{
Class newClass =
calloc(1, sizeof(struct objc_class) + sizeof(struct reference_list));
if (Nil == newClass) { return Nil; }
// Set up the new class
newClass->isa = superclass->isa;
newClass->name = superclass->name;
// Uncomment this for debugging: it makes it easier to track which hidden
// class is which
// static int count;
//asprintf(&newClass->name, "%s%d", superclass->name, count++);
newClass->info = objc_class_flag_resolved |
objc_class_flag_class | objc_class_flag_user_created |
objc_class_flag_new_abi | objc_class_flag_hidden_class |
objc_class_flag_assoc_class;
newClass->super_class = superclass;
newClass->dtable = uninstalled_dtable;
newClass->instance_size = superclass->instance_size;
LOCK_RUNTIME_FOR_SCOPE();
newClass->sibling_class = superclass->subclass_list;
superclass->subclass_list = newClass;
return newClass;
}
static inline Class initHiddenClassForObject(id obj)
{
Class hiddenClass = allocateHiddenClass(obj->isa);
assert(!class_isMetaClass(obj->isa));
static SEL cxx_destruct;
if (NULL == cxx_destruct)
{
cxx_destruct = sel_registerName(".cxx_destruct");
}
const char *types = sizeof(void*) == 4 ? "v8@0:4" : "v16@0:8";
class_addMethod(hiddenClass, cxx_destruct,
(IMP)deallocHiddenClass, types);
obj->isa = hiddenClass;
return hiddenClass;
}
static void deallocHiddenClass(id obj, SEL _cmd)
{
LOCK_RUNTIME_FOR_SCOPE();
Class hiddenClass = findHiddenClass(obj);
// After calling [super dealloc], the object will no longer exist.
// Free the hidden class.
struct reference_list *list = object_getIndexedIvars(hiddenClass);
DESTROY_LOCK(&list->lock);
cleanupReferenceList(list);
freeReferenceList(list->next);
fprintf(stderr, "Deallocating dtable %p\n", hiddenClass->dtable);
free_dtable(hiddenClass->dtable);
// We shouldn't have any subclasses left at this point
assert(hiddenClass->subclass_list == 0);
// Remove the class from the subclass list of its superclass
Class sub = hiddenClass->super_class->subclass_list;
if (sub == hiddenClass)
{
hiddenClass->super_class->subclass_list = hiddenClass->sibling_class;
}
else
{
while (sub != NULL)
{
if ((Class)sub->sibling_class == hiddenClass)
{
sub->sibling_class = hiddenClass->sibling_class;
break;
}
sub = sub->sibling_class;
}
}
// Free the class
free(hiddenClass);
}
static struct reference_list* referenceListForObject(id object, BOOL create)
{
if (class_isMetaClass(object->isa))
{
Class cls = (Class)object;
if ((NULL == cls->extra_data) && create)
{
volatile int *lock = lock_for_pointer(cls);
struct reference_list *list = gc->malloc(sizeof(struct reference_list));
lock_spinlock(lock);
if (NULL == cls->extra_data)
{
INIT_LOCK(list->lock);
cls->extra_data = list;
unlock_spinlock(lock);
}
else
{
unlock_spinlock(lock);
gc->free(list);
}
}
return cls->extra_data;
}
Class hiddenClass = findHiddenClass(object);
if ((NULL == hiddenClass) && create)
{
volatile int *lock = lock_for_pointer(object);
lock_spinlock(lock);
hiddenClass = findHiddenClass(object);
if (NULL == hiddenClass)
{
hiddenClass = initHiddenClassForObject(object);
struct reference_list *list = object_getIndexedIvars(hiddenClass);
INIT_LOCK(list->lock);
}
unlock_spinlock(lock);
}
return hiddenClass ? object_getIndexedIvars(hiddenClass) : NULL;
}
void objc_setAssociatedObject(id object,
void *key,
id value,
objc_AssociationPolicy policy)
{
if (isSmallObject(object)) { return; }
struct reference_list *list = referenceListForObject(object, YES);
setReference(list, key, value, policy);
}
id objc_getAssociatedObject(id object, void *key)
{
if (isSmallObject(object)) { return nil; }
struct reference_list *list = referenceListForObject(object, NO);
if (NULL == list) { return nil; }
struct reference *r = findReference(list, key);
if (NULL != r)
{
return r->object;
}
if (class_isMetaClass(object->isa))
{
return nil;
}
Class cls = object->isa;
while (Nil != cls)
{
while (Nil != cls &&
!objc_test_class_flag(cls, objc_class_flag_assoc_class))
{
cls = class_getSuperclass(cls);
}
if (Nil != cls)
{
struct reference_list *next_list = object_getIndexedIvars(cls);
if (list != next_list)
{
list = next_list;
struct reference *r = findReference(list, key);
if (NULL != r)
{
return r->object;
}
}
cls = class_getSuperclass(cls);
}
}
return nil;
}
void objc_removeAssociatedObjects(id object)
{
if (isSmallObject(object)) { return; }
cleanupReferenceList(referenceListForObject(object, NO));
}
PRIVATE void *gc_typeForClass(Class cls)
{
struct reference_list *list = referenceListForObject(cls, YES);
return list->gc_type;
}
PRIVATE void gc_setTypeForClass(Class cls, void *type)
{
struct reference_list *list = referenceListForObject(cls, YES);
list->gc_type = type;
}
int objc_sync_enter(id object)
{
if ((object == 0) || isSmallObject(object)) { return 0; }
struct reference_list *list = referenceListForObject(object, YES);
LOCK(&list->lock);
return 0;
}
int objc_sync_exit(id object)
{
if ((object == 0) || isSmallObject(object)) { return 0; }
struct reference_list *list = referenceListForObject(object, NO);
if (NULL != list)
{
UNLOCK(&list->lock);
return 0;
}
return 1;
}
static Class hiddenClassForObject(id object)
{
if (isSmallObject(object)) { return nil; }
if (class_isMetaClass(object->isa))
{
return object->isa;
}
Class hiddenClass = findHiddenClass(object);
if (NULL == hiddenClass)
{
volatile int *lock = lock_for_pointer(object);
lock_spinlock(lock);
hiddenClass = findHiddenClass(object);
if (NULL == hiddenClass)
{
hiddenClass = initHiddenClassForObject(object);
struct reference_list *list = object_getIndexedIvars(hiddenClass);
INIT_LOCK(list->lock);
}
unlock_spinlock(lock);
}
return hiddenClass;
}
BOOL object_addMethod_np(id object, SEL name, IMP imp, const char *types)
{
return class_addMethod(hiddenClassForObject(object), name, imp, types);
}
IMP object_replaceMethod_np(id object, SEL name, IMP imp, const char *types)
{
return class_replaceMethod(hiddenClassForObject(object), name, imp, types);
}
static char prototypeKey;
id object_clone_np(id object)
{
if (isSmallObject(object)) { return object; }
// Make sure that the prototype has a hidden class, so that methods added
// to it will appear in the clone.
referenceListForObject(object, YES);
id new = class_createInstance(object->isa, 0);
Class hiddenClass = initHiddenClassForObject(new);
struct reference_list *list = object_getIndexedIvars(hiddenClass);
INIT_LOCK(list->lock);
objc_setAssociatedObject(new, &prototypeKey, object,
OBJC_ASSOCIATION_RETAIN_NONATOMIC);
return new;
}
id object_getPrototype_np(id object)
{
return objc_getAssociatedObject(object, &prototypeKey);
}