C + + STL Source Analysis Learning Notes (i)

Template <class Inputiterator, class forwarditerator>
Inline ForwardIterator uninitialized_copy (inputiterator First, inputiterator last,forwarditerator result)

Function Use Example

#include <algorithm> #include <iostream> #include <memory> #include <string> #include <tuple > #include <vector>class int{public:int (int x): val (x) {} Int get () {return val;} Private:int Val;}; int main () {     int a1[]={1,2,3,4,5,6,7};     const int N = sizeof (A1)/sizeof (int);     int* a2= (int*) malloc (N * sizeof (INT));     Std::uninitialized_copy (A1,A1+N,A2);     for (int i = 0; i < N; ++i) {         std::cout << a2[i].get () << "";     }}

Uninitialized_copy Initializes a series of int elements at A2 's address, where the data is copied from the A1 array

Follow-up source to view Uninitialized_copy () workflow (source code STL source analysis with the book Codes Tass-sgi-stl-2.91.57-source)

Template <class Inputiterator, class forwarditerator>
Inline ForwardIterator uninitialized_copy (inputiterator First, inputiterator last, forwarditerator result)

--->

__uninitialized_copy (First, last, result, value_type (result));

--->

__uninitialized_copy_aux (First, last, result, is_pod ());

--->

Template <class Inputiterator, class forwarditerator>
Inline ForwardIterator
__uninitialized_copy_aux (inputiterator First, Inputiterator last,
ForwardIterator result,
__true_type) {
Return copy (First, last, result);
}

Template <class Inputiterator, class forwarditerator>
ForwardIterator
__uninitialized_copy_aux (inputiterator First, Inputiterator last,
ForwardIterator result,
__false_type) {
ForwardIterator cur = result;
__stl_try {
for (; first! = last; ++first, ++cur)
Construct (&*cur, *first);
return cur;
}
__stl_unwind (Destroy (result, cur));
}

The main thing is uninitialized_copy () call __uninitialized_copy () The last argument is value_type (result)

Value_type (Result) is the function of converting forwarditerator result to pointer type T

Call __uninitialized_copy_aux () in __uninitialized_copy () is to determine if T is pod type

How do I tell if it is pod type?

typedef typename __TYPE_TRAITS<T>::IS_POD_TYPE Is_pod;

All the basic types are defined as follows

struct __type_traits<char> {
typedef __true_type IS_POD_TYPE;
};

struct __type_traits<signed char> {
typedef __true_type IS_POD_TYPE;
};

struct __type_traits<int> {
typedef __true_type IS_POD_TYPE;
};

Instead of the base type, it corresponds to the following template code

Template <class type>
struct __type_traits {
typedef __false_type IS_POD_TYPE;
};

So when TypeName __type_traits<t>::is_pod_type's T is int char double type

Is_pod_type to __true_type

Other types are

Is_pod_type to __false_type

If it is pod type, it is the basic data type (int char double, etc.) then copy directly

The code is as follows

__true_type
Return copy (First, last, result);

If it is not pod type, you need to call the constructor in turn to create the data

The code is as follows

__false_type
for (; first! = last; ++first, ++cur)
Construct (&*cur, *first);

C + + STL Source Analysis Learning Note (i)