简单空间配置器

一个简单的空间配置器, JJ::allocator:

<span style="font-family:Courier New;font-size:14px;">#ifndef __JJALLOC_#define __JJALLOC_#include <new>// for placement new#include <cstddef>// for ptrdiff_t, size_t#include <cstdlib>// for exit()#include <climits>// for UINT_MAX#include <iostream>// for cerrnamespace 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. 将p作为地址传入operate new函数//不进行分配操作, 调用T1::T1(value)}template <class T>inline void _destroy(T* ptr) {ptr->~T();}template <class T>class allocator {public:typedef Tvalue_type;typedef T*pointer;typedef const T*const_pointer;typedef T&reference;typedef const T&const_reference;typedef size_tsize_type;typedef ptrdiff_tdifference_type;template <class U>struct rebind {typedef allocator<U> other; //以list为例, allocator<int>::rebind<node>::other即为allocator<node>};//第二个参数是个提示, 实现上可能会利用它来增进区域性(locality), 或者完全忽略之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</span>

SGI标准空间配置器, std::allocator源码:

<span style="font-family:Courier New;font-size:14px;">#ifndef DEFALLOC_H#define DEFALLOC_H#include <new.h>#include <stddef.h>#include <stdlib.h>#include <limits.h>#include <iostream.h>#include <algobase.h>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 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;    pointer allocate(size_type n) { return ::allocate((difference_type)n, (pointer)0);    }    void deallocate(pointer p) { ::deallocate(p); }    pointer address(reference x) { return (pointer)&x; }    const_pointer const_address(const_reference x) { return (const_pointer)&x;     }    size_type init_page_size() { return max(size_type(1), size_type(4096/sizeof(T)));     }    size_type max_size() const { return max(size_type(1), size_type(UINT_MAX/sizeof(T)));     }};//模板特化需要加template<>, 此处为gcc特性class allocator<void> {   public:    typedef void* pointer;};#endif</span>