本文原创

stl_uninitialized.h 头文件主要包含 uninitialized_copy、uninitialized_copy_n、uninitialized_fill、uninitialized_fill_n、__uninitialized_copy_copy、__uninitialized_copy_fill、__uninitialized_fill_copy。

template <class _InputIter, class _ForwardIter>
inline _ForwardIter __uninitialized_copy_aux(_InputIter __first, _InputIter __last,
                                             _ForwardIter __result, __true_type)
{
    return copy(__first, __last, __result);
}

template <class _InputIter, class _ForwardIter>
_ForwardIter __uninitialized_copy_aux(_InputIter __first, _InputIter __last,
                                      _ForwardIter __result, __false_type)
{
    _ForwardIter __cur = __result;
    __STL_TRY {
        for ( ; __first != __last; ++__first, ++__cur)
            _Construct(&*__cur, *__first);
        return __cur;
    }
    __STL_UNWIND(_Destroy(__result, __cur));
}

template <class _InputIter, class _ForwardIter, class _Tp>
inline _ForwardIter
__uninitialized_copy(_InputIter __first, _InputIter __last,
                     _ForwardIter __result, _Tp*)
{
    typedef typename __type_traits<_Tp>::is_POD_type _Is_POD;
    return __uninitialized_copy_aux(__first, __last, __result, _Is_POD());
}

template <class _InputIter, class _ForwardIter>
inline _ForwardIter uninitialized_copy(_InputIter __first, _InputIter __last,
                                       _ForwardIter __result)
{
    return __uninitialized_copy(__first, __last, __result, __value_type(__result));
}

inline char* uninitialized_copy(const char* __first, const char* __last, char* __result)
{
    memmove(__result, __first, __last - __first);
    return __result + (__last - __first);
}

inline wchar_t* uninitialized_copy(const wchar_t* __first, const wchar_t* __last, wchar_t* __result)
{
    memmove(__result, __first, sizeof(wchar_t) * (__last - __first));
    return __result + (__last - __first);
}

技巧仍是根据 __value_type 萃取出类型后选择不同的实现，这里若不是 POD 类型需要调用被拷贝对象构造函数（初始化值就是被拷贝处迭代器的解引用），这一般是深拷贝，若是 POD 类型则直接调用 copy 函数模板，进行浅拷贝。

template <class _ForwardIter, class _Tp>
inline void __uninitialized_fill_aux(_ForwardIter __first, _ForwardIter __last, const _Tp& __x, __true_type)
{
    fill(__first, __last, __x);
}

template <class _ForwardIter, class _Tp>
void __uninitialized_fill_aux(_ForwardIter __first, _ForwardIter __last, const _Tp& __x, __false_type)
{
    _ForwardIter __cur = __first;
    __STL_TRY {
        for ( ; __cur != __last; ++__cur)
            _Construct(&*__cur, __x);
    }
    __STL_UNWIND(_Destroy(__first, __cur));
}

template <class _ForwardIter, class _Tp, class _Tp1>
inline void __uninitialized_fill(_ForwardIter __first, 
                                 _ForwardIter __last, const _Tp& __x, _Tp1*)
{
    typedef typename __type_traits<_Tp1>::is_POD_type _Is_POD;
    __uninitialized_fill_aux(__first, __last, __x, _Is_POD());               
}

template <class _ForwardIter, class _Tp>
inline void uninitialized_fill(_ForwardIter __first, _ForwardIter __last, const _Tp& __x)
{
    __uninitialized_fill(__first, __last, __x, __value_type(__first));
}

同样，__uninitialized_fill 也是根据是否是 POD 类型进行区分对待。

// __uninitialized_copy_copy :
// Copies [first1, last1) into [result, result + (last1 - first1)), and
//  copies [first2, last2) into [result, result + (last1 - first1) + (last2 - first2)).
template <class _InputIter1, class _InputIter2, class _ForwardIter>
inline _ForwardIter
__uninitialized_copy_copy(_InputIter1 __first1, _InputIter1 __last1,
                          _InputIter2 __first2, _InputIter2 __last2,
                          _ForwardIter __result)
{
    _ForwardIter __mid = uninitialized_copy(__first1, __last1, __result);
    __STL_TRY {
        return uninitialized_copy(__first2, __last2, __mid);
    }
    __STL_UNWIND(_Destroy(__result, __mid));
}

// __uninitialized_fill_copy :
// Fills [result, mid) with x, and copies [first, last) into [mid, mid + (last - first)).
template <class _ForwardIter, class _Tp, class _InputIter>
inline _ForwardIter
__uninitialized_fill_copy(_ForwardIter __result, _ForwardIter __mid,
                          const _Tp& __x,
                          _InputIter __first, _InputIter __last)
{
    uninitialized_fill(__result, __mid, __x);
    __STL_TRY {
         return uninitialized_copy(__first, __last, __mid);
    }
    __STL_UNWIND(_Destroy(__result, __mid));
}

// __uninitialized_copy_fill :
// Copies [first1, last1) into [first2, first2 + (last1 - first1)), and fills [first2 + (last1 - first1), last2) with x.
template <class _InputIter, class _ForwardIter, class _Tp>
inline void
__uninitialized_copy_fill(_InputIter __first1, _InputIter __last1,
                          _ForwardIter __first2, _ForwardIter __last2,
                          const _Tp& __x)
{
    _ForwardIter __mid2 = uninitialized_copy(__first1, __last1, __first2);
    __STL_TRY {
        uninitialized_fill(__mid2, __last2, __x);
    }
    __STL_UNWIND(_Destroy(__first2, __mid2));
}