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