浅析android中getStrongProxyForHandle函数动态申请索引对应的内存空间

浅析android中getStrongProxyForHandle函数动态申请handle索引对应的vector内存空间

class ProcessState : public virtual RefBase
{
    ...
    struct handle_entry {
        IBinder* binder;
        RefBase::weakref_type* refs;
    };
    ...
    Vector<handle_entry>mHandleToObject;//从模板定义一个大小为sizeof(handle_entry)的Vector变量mHandleToObject
    ...
}

ProcessState::handle_entry* ProcessState::lookupHandleLocked(int32_t handle)
{
    const size_t N=mHandleToObject.size();//开始N等于0
    if (N <= (size_t)handle) {
        handle_entry e;
        e.binder = NULL;//初始化该handle索引对应的结构体struct handle_entry
        e.refs = NULL;
        status_t err = mHandleToObject.insertAt(e, N, handle+1-N);//在Vector的最后位置,动态生长该Vector类中成员
        if (err < NO_ERROR) return NULL;
    }
    return &mHandleToObject.editItemAt(handle);//这样将返回handle作为索引,对应的空闲struct handle_entry结构体内存空间指针

}

include/utils/Vector.h
对Vector模板进行了定义：
template<class TYPE> inline
Vector<TYPE>::Vector()
    : VectorImpl(sizeof(TYPE),
                ((traits<TYPE>::has_trivial_ctor ? HAS_TRIVIAL_CTOR : 0)
                |(traits<TYPE>::has_trivial_dtor ? HAS_TRIVIAL_DTOR : 0)
                |(traits<TYPE>::has_trivial_copy ? HAS_TRIVIAL_COPY : 0)
                |(traits<TYPE>::has_trivial_assign ? HAS_TRIVIAL_ASSIGN : 0))
                )
{
}

template<class TYPE> inline
ssize_t vector<TYPE>::insertAt(const TYPE& item, size_t index, size_t numItems) {
    return vectorimpl::insertAt(&item, index, numItems);
}

ssize_t vectorimpl::insertAt(const void* item, size_t index, size_t numItems)
{
    if (index > size())//最开始等于0,所以0 > 0将不成立
        return BAD_INDEX;
    void* where = _grow(index, numItems);//malloc内存空间
    if (where) {
        if (item) {
            _do_splat(where, item, numItems);
        } else {
            _do_construct(where, numItems);
        }
    }
    return where ? index : (ssize_t)NO_MEMORY;
}

template<class TYPE> inline
TYPE& Vector<TYPE>::editItemAt(size_t index) {
    return *( static_cast<TYPE *>(editItemLocation(index)) );
}

void* VectorImpl::editItemLocation(size_t index)
{
    LOG_ASSERT(index<capacity(),
        "[%p] itemLocation: index=%d, capacity=%d, count=%d",
        this, (int)index, (int)capacity(), (int)mCount);
            
    void* buffer = editArrayImpl();
    if (buffer)
        return reinterpret_cast<char*>(buffer) + index*mItemSize;//返回index索引对应的buffer存储空间首指针
    return 0;
}