以STL的運(yùn)用角度而言，空間配置器時(shí)最不需要介紹的東西，它總是隱藏在一切組件的背后，整個(gè)STL的操作對(duì)象（所有的數(shù)值）都存放在容器之內(nèi)，而容器一定需要配置空間以置放資料。下面是一個(gè)簡單空間配置器代碼（來自 STL源碼剖析）：
//jjalloc.h
#ifndef _JJALLOC_
#define _JJALLOC_
#include<new>
#include<cstddef>
#include<cstdlib>
#include<climits>
#include<iostream>
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);//placement new operator
}
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));
}
};
}//end of namespace JJ
#endif
//jjalloc.cc,測試上面這個(gè)簡單的配置器
#include"jjalloc.h"
#include<vector>
#include<iostream>
using namespace std;
int main()
{
int ia[5]={0,1,2,3,4};
unsigned int i;
vector<int,JJ::allocator<int> >iv(ia,ia+5);
for(i=0;i<iv.size();i++)
cout<<iv[i]<<' ';
cout<<endl;
}