为什么不说allocator是内存配置器而说是空间配置器，因为空间不一定是内存，也可以是磁盘或其他辅助介质。是的，你可以写一个allocator，直接向硬盘取空间。sgi stl提供的配置器，配置的对象是内存。
stl中allocator用法参考以前的http://www.cnblogs.com/youxin/archive/2012/06/07/2540170.html。
书中jj allocator类
#ifndef _JJALLOC
#define _JJALLOC
#include<new> //for placement new
#include<cstddef> //for ptrdiff_t ,size_t
#include<cstdlib> //for exit()
#include<climits> //for UINX_MAX
#include<iostream> //for cerr namespace JJ
{
template<class T>
inline T* _allocate(ptrdiff_t size,T*)
{
set_new_handler();
T* tmp=(T*)(::operator new((size_t)(size*sizeof(T))));
if(tmp==)
{
cerr<<"out of memory"<<endl;
exit();
}
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,invoke constuctor of t1
} 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; //rebind allocator of type U
template<class U>
struct rebind{
typedef allocator<U> other;
};
//需要加上以下2个函数，windows的编译器用到了allocator不同类型的拷贝，
allocator()
{
return ;
} template <class U>
allocator(const allocator<U>& c )
{
} //hint user for locality,第2个参数是个提示，实现上可能会利用它来增进区域性（locality），或完全忽略之 pointer allocate(size_type n,const void* hint=)
{
return _allocate((difference_type)n,(pointer));
} 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
#include"2jjalloc.h"
#include<vector>
#include<iostream>
using namespace std; int main()
{
int ia[]={,,,,};
unsigned int i; vector<int,JJ::allocator<int> > iv(ia,ia+);
for(i=;i<iv.size();i++)
cout<<iv[i]<<ends;
cout<<endl;
}
这个allocator只能有限程序带票PJ STL，