Refbase, SP and WP (2)

1. Example of creating an SP through WP, such as:

int main () {

A * PA = new A ();

Wp<a> WpA (PA); The weak reference count is 1, and the strong reference count is the initial value 0x1000000.

sp<a> SpA = Wpa.promote (); Get an SP through promote ().

}

2. Implementation of the promote function:

Template<typename t>

Sp<t> wp<t>::p romote () const {

Retrun sp<t> (m_ptr, m_refs); Call the SP constructor.

}

3. Template<typename t>

SP<T>::SP (t* p, weakref_type* refs)

: M_ptr (P && refs->attemptincstrong (This)) p:0) {

}

4. BOOL Refbase::weakref_type::attemptincstrong (const void* ID) {

Incweak (ID); Adds a reference count, at which point the weak reference count is 2.

weakref_impl* Const IMPL = static_cast<weakref_impl*> (this);

int32_t Curcount = impl->mstrong; This is still the initial value

while (Curcount > 0 && curcount! = initial_strong_value) {

if (Android_atomic_cmpxchg (Curcount, Curcount + 1, &impl->mstrong) = = 0) {

Break

}

Curcount = impl->mstrong;

}

if (curcount <= 0 | | curcount = = initial_strong_value) {

BOOL Allow;

if (Curcount = = Initial_strong_value) {

Allow = (impl->mflags&object_lifetime_weak)! = Objece_lifetime_weak | | Impl->mbase->onincstrongattempted (First_inc_strong, id);

} else {

Allow = (impl->mflags&object_lifetime_weak)! = Objece_lifetime_weak && impl->mbase-> Onincstrongattempted (First_inc_strong, id);

}

if (!allow) {

Decweak (ID); The weak is not allowed to be strong, if the reference count minus 1, came in with the addition of 1.

return false;

}

Curcount = Android_atomic_inc (&impl->mstrong); Allowed by weak to strong, strong reference count plus 1.

if (Curcount > 0 && curcount < initial_strong_value) {

Impl->mbase->onlaststrongref (ID);

}

}

if (Curcount = = Initial_strong_value) {

Android_atomic_add (-initial_strong_value, &impl->mstrong); The strong reference count becomes 1.

Impl->mbase->onfirstref ();

}

return true;

}

Refbase, SP and WP (2)