《STL源码剖析》学习笔记

jjalloc.h

#ifndef  JJALLOC_H#define JJALLOC_H#include
     
      #include 
      
       #include
       
        #include
        
         #include 
         
          namespace JJ{template
          
           inline T* _allocate(ptrdiff_t size,T*){ /*set_new_handler则是一个输入并返回 new_handler类型的函数。set_new_handler的 输入参数是operator new分配内存失败时要调 用的出错处理函数的指针，返回值 是set_new_handler没调用之前就 已经在起作用的旧的出错处理函数的指针*/ set_new_handler(0); T* tem=(T*)(::operator new((size_t)(size *sizeof(T)))); if(tem==0){ cout<<"out of memory"<
           
            inline void _deallocate(T* buffer){ ::operator delete(buffer);} template
            
             inline void _construct(T1* p,const T2& value){ new(p) T1(value);}template
             
              inline void _destroy(T* ptr){ ptr->~T();}template
              
               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 alloctor of type u template
               
                 struct rebind{ typedef allocator
                 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 //JJALLOC_H
               
              
             
            
           
          
         
        
       
      
     

测试代码：

#include "jjalloc.h"#include
     
      using namespace std;class Test{  public:      int x;      Test(int b=0){          x=b;                }      ~Test(){      }};int main(){    int x=4;    JJ::allocator
      
        a;    JJ::allocator
       
         b;    int *p=a.allocate(1);    Test *t=new Test;    //new(p) T1(value) 这叫place new,在指针p所指向的内存空间创建一个    //类型为T1的对象。调用的构造函数接受一个类型为const //    T2&（或其他兼容类型）的参数//    new(&t) Test(x);    b.construct(t,x);    *p=1;    cout<<*p<
        
         x<