Binder进程与线程ProcessState以及IPCThreadState

sp ProcessState::getContextObject(const sp& /*caller*/)
{
    return getStrongProxyForHandle(0);
}

sp ProcessState::getStrongProxyForHandle(int32_t handle)
{
    sp result;
 
    AutoMutex _l(mLock);
 
    handle_entry* e = lookupHandleLocked(handle);
 
    if (e != NULL) {
        ......
        IBinder* b = e->binder;
        if (b == NULL || !e->refs->attemptIncWeak(this)) {
            if (handle == 0) {
               ......
                Parcel data;
                status_t status = IPCThreadState::self()->transact(
                        0, IBinder::PING_TRANSACTION, data, NULL, 0);
                if (status == DEAD_OBJECT)
                   return NULL;
            }
 
            b = new BpBinder(handle); 
            e->binder = b;
            if (b) e->refs = b->getWeakRefs();
            result = b;
        } else {
            // This little bit of nastyness is to allow us to add a primary
            // reference to the remote proxy when this team doesn‘t have one
            // but another team is sending the handle to us.
            result.force_set(b);
            e->refs->decWeak(this);
        }
    }
 
    return result;
}

ProcessState::handle_entry* ProcessState::lookupHandleLocked(int32_t handle)
{
    const size_t N=mHandleToObject.size();
    if (N  (size_t)handle) {
        handle_entry e;
        e.binder = NULL;
        e.refs = NULL;
        status_t err = mHandleToObject.insertAt(e, N, handle+1-N);
        if (err return NULL;
    }
    return &mHandleToObject.editItemAt(handle);
}

sp b = ProcessState::self()->getContextObject(NULL);