STL之空间配置器(一)

听名字就是他是为了给我们提供足够的空间而默默的服务着；

下面介绍一个简单的空间配置器JJ:allocator

//demo3.h
#include <new>
#include <cstddef>
#include <cstdlib>
#include <climits>
#include <iostream>

namespace JJ
{
	template <class T>//分配内存，相当于构造
	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>//相当于析构
	inline void _deallocate(T* buffer){
		::operator delete(buffer);
	}

	template<class T1,class T2>
	inline void _construct(T1* p,const T2& value){
		new (p) T2(value);//这边原来的是new (p)	T1(value)对照源码来讲边应该是T2
	}

	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));
		}
	};
}

　　

#include "demo3.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;
}

　　上面通过STLPort可编译过