在STL中設計了一個默認的空間配置器來負責內存的申請與釋放，因此在每種容器中比如vector中如果不顯示的指定使用何種空間配置器將調用默認的空間配置器，一般通用的代碼如下：
#include<vector>#include<iostream>
using namespace std;
int main(){
int ia[]={0,1,5,3,4};
unsigned int i;
vector<int > iv(ia,ia+5);
for(i=0;i<iv.size();i++){
cout<<iv[i]<<" ";
}
cout<<endl;
return 0;
}
在上述代碼中將使用默認的空間配置器std::allocator,除了使用默認的空間配置器外還可以自己完成。根據STL規範，allocator的必要接口，完成一個簡單的空間配置器如下:
/*
* 2jjalloc.h
*
* Created on: 2013-6-15
* Author: mwjsolar
*/
#ifndef _2JJALLOC_H_
#define _2JJALLOC_H_
#include<new>
#include<cstddef>
#include<cstdlib>
#include<climits>
#include<iostream>
#include<memory>
using namespace std;
namespace JJ{
template<class T>
inline T* _allocate(ptrdiff_t size,T*){
set_new_handler(0);
T* tmp=(T*)(::operator new ((size_t)(size*sizeof(T))));
if(tmp==0){
cerr<<"out of memory "<<endl;
exit(1);
}
return tmp;
}
template<class T>
inline void _deallocate(T* buffer){
::operator delete (buffer);
}
template <class T1,class T2>
inline void _construct(T1* p,const T2& value){
new(p) T1(value);
}
template <class T>
inline void _destroy(T* ptr){
ptr->~T();
}
template<class T>
class allocator{
public:
typedef T value_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T& reference;
typedef const T& const_reference;
typedef size_t size_type ;
typedef ptrdiff_t difference_type;
template<class U>
struct rebind{
typedef allocator<U> other;
};
pointer allocate(size_type n,const void *hint=0){
return _allocate((difference_type)n,(pointer)0);
}
void deallocate(pointer p,size_type n){
_deallocate(p);
}
void construct(pointer p,const T& value){
_construct(p,value);
}
void destroy(pointer p){
_destroy(p);
}
pointer address(reference x){
return (pointer)&x;
}
const_pointer const_address(const_reference x){
return (const_pointer)&x;
}
size_type max_size()const{
return size_type(UINT_MAX/sizeof(T));
}
};
}
#endif /* 2JJALLOC_H_ */
cpp文件如下：
/*
* 2jjalloc.cpp
*
* Created on: 2013-6-15
* Author: mwjsolar
*/
#include"2jjalloc.h"
#include<vector>
#include<iostream>
using namespace std;
/*
* 2jjalloc.h
*
* Created on: 2013-6-15
* Author: mwjsolar
*/
int main(){
int ia[]={0,1,5,3,4};
unsigned int i;
vector<int ,JJ::allocator<int> > iv(ia,ia+5);
for(i=0;i<iv.size();i++){
cout<<iv[i]<<" ";
}
cout<<endl;
return 0;
}
將vector中的參數設爲JJ::allocator<int>，調用自定義的空間配置器。