为C++标准库容器写自己的内存分配程序

为C++标准库容器写自己的内存分配程序

根据sgi 的STL源码的二级分配算法改写的内存池分配程序，只要稍微修改就可以实现共享内存方式管理，使用C++标准库容器中的map，set，multimap，multiset测试通过，vector测试通不过，原因是在内存回收的时候考虑的比较简单，vector每次分配内存个数不固定，回收也不固定，这样的话，程序还需要继续完善。

　　

内存池管理程序源码如下：

以下是引用片段：

以下是代码片段： #ifndef MY_ALLOCATOR_H_ #define MY_ALLOCATOR_H_ #include "stdafx.h" #include <limits> #include <iostream> namespace happyever  {   enum { NODENUMS = 2 };   union _Obj    {     union _Obj* M_free_list_link;     char M_client_data[1];       } ;   typedef union _Obj Obj;   struct _Cookie   {     int iShmKey;        /* 共享内存键值 */     int iShmID;         /* iShmKey对应的shmid */     int iSemKey;        /* 锁信号键值 */     int iSemID;         /* 锁信号标识 */     int iTotalsize;    /* 容器总容量 */     void* pStartall;   /* 共享内存自身地址 */     char* pStartfree;  /* 自由空间的开始地址*/     char* pEndfree;    /* 自由空间的结束地址*/     int iUseNum[NODENUMS];     /*用来存放free_list中节点的size*/     short sFreelistIndex[NODENUMS];     /*存放分配内存节点的链表*/     Obj* uFreelist[NODENUMS];   };   typedef struct _Cookie Cookie;   //Obj;   //Cookie;   static Cookie *pHead = NULL;   template <class T>   class MyAlloc    {   private:     static const int ALIGN = sizeof(Obj);     int round_up(int bytes);     int freelist_index(int bytes);     int freelist_getindex(int bytes);     char* chunk_alloc(int size, int *nobjs);     void* refill(int num,int n);   public:     // type definitions     typedef T        value_type;     typedef T*       pointer;     typedef const T* const_pointer;     typedef T&       reference;     typedef const T& const_reference;     typedef std::size_t    size_type;     typedef std::ptrdiff_t difference_type;     template <class U>     struct rebind      {       typedef MyAlloc<U> other;     };     pointer address (reference value) const      {       return &value;     }     const_pointer address (const_reference value) const      {       return &value;     }     MyAlloc() throw()      {       std::cout<<"MyAlloc"<<std::endl;     }     MyAlloc(const MyAlloc& x) throw()      {       std::cout<<"const MyAlloc"<<std::endl;     }     template <class U>     MyAlloc (const MyAlloc<U>& x) throw()     {       std::cout<<"const MyAlloc<U>"<<std::endl;     }     ~MyAlloc() throw()      {       std::cout<<"~MyAlloc"<<std::endl;     }     size_type max_size () const throw()      {       return std::numeric_limits<std::size_t>::max() / sizeof(T);     }     //void PrintFreelistAndCookie();     pointer allocate (size_type num, const void* = 0)      {       pointer ret = 0;       Obj** my_free_list;       Obj* result;       int index;       // print message and allocate memory with global new       std::cerr << "allocate " << num << " element(s)"         << " of size " << sizeof(T) << std::endl;       index = freelist_index(sizeof(T));       if(index >= NODENUMS)       {         return NULL;       }       my_free_list = pHead->uFreelist + index;       //Lock(semid,LOCK_NUM);       result = *my_free_list;       if (result == 0)       {         ret = (pointer)refill((int)num, round_up(sizeof(T)));       }       else       {         *my_free_list = result->M_free_list_link;         ret = (pointer)result;       }       //UnLock(semid,LOCK_NUM);       pHead->iUseNum[index] = pHead->iUseNum[index] + (int)num;       if(0 == ret)       {         std::cerr << "alloc memory fail!" << std::endl;         exit(1);       }       std::cerr << " allocated at: " << (void*)ret << std::endl;       PrintFreelistAndCookie();       return ret;     }     void construct (pointer p, const T& value)      {       // initialize memory with placement new       new((void*)p)T(value);     }     void destroy (pointer p)      {       // destroy objects by calling their destructor       p->~T();     }     void deallocate (pointer p, size_type num)      {       Obj** my_free_list;       Obj* q ;       int index;       index = freelist_getindex(sizeof(T));       if(index >= NODENUMS)       {         std::cerr << "deallocate memory fail!" << std::endl;         exit(1);       }       my_free_list = pHead->uFreelist + index;       q = (Obj*) p;       //Lock(semid,LOCK_NUM);       /*这个地方可能会有问题*/       //for(int i=0 ;i<(int)num ; i++)       {         q->M_free_list_link = *my_free_list;         *my_free_list = q;       }       //UnLock(semid,LOCK_NUM);       pHead->iUseNum[index] = pHead->iUseNum[index] - (int)num;              std::cerr << "deallocate " << num << " element(s)"         << " of size " << sizeof(T)         << " at: " << (void*)p << std::endl;       PrintFreelistAndCookie();     }   };   template <class T>   int MyAlloc<T>::round_up(int bytes)   {     int i;     i = bytes;     if(bytes < ALIGN)     {       i = ALIGN;     }     std::cout<<"round_up:bytes="<<bytes<<" , return="<<i<<std::endl;     return i;   };   template <class T>   int MyAlloc<T>::freelist_index(int bytes)   {     int i;     for(i=0 ; i< NODENUMS ; i++)     {       if(pHead->sFreelistIndex[i] == bytes)         break;     }     if(i >= NODENUMS)     {       for(i=0 ; i< NODENUMS ; i++)       {         if(pHead->sFreelistIndex[i] == 0)         {           pHead->sFreelistIndex[i] = bytes;           std::cout<<"freelist_index:bytes="<<bytes<<" , return="<<i<<std::endl;           return i;         }       }     }     std::cout<<"freelist_index:bytes="<<bytes<<" , return="<<i<<std::endl;     return i;   };   template <class T>   int MyAlloc<T>::freelist_getindex(int bytes)   {     int i;     for(i=0 ; i< NODENUMS ; i++)     {       if(pHead->sFreelistIndex[i] == bytes)         break;     }     std::cout<<"freelist_getindex:bytes="<<bytes<<" , return="<<i<<std::endl;     return i;   };   template <class T>   char* MyAlloc<T>::chunk_alloc(int size, int *nobjs)   {     char* result;     int counts = *nobjs;     int total_bytes = size * counts;     int bytes_left = int(pHead->pEndfree - pHead->pStartfree);     std::cout<<"chunk_alloc:total_bytes = "<<total_bytes       <<",bytes_left = "<<bytes_left<<std::endl;     if (bytes_left >= total_bytes)     {       result = pHead->pStartfree;       pHead->pStartfree += total_bytes;       std::cout<<"chunk_alloc:total_bytes = "<<total_bytes         <<",result = "<<*result<<",start_free = "<<&(pHead->pStartfree)<<std::endl;     }     else if (bytes_left >= size)     {       counts = bytes_left/size;       total_bytes = size * counts;       result = pHead->pStartfree;       pHead->pStartfree += total_bytes;       *nobjs = counts;       std::cout<<"chunk_alloc:total_bytes = "<<total_bytes<<",nobjs = "<<nobjs         <<",result = "<<*result<<",start_free = "<<&(pHead->pStartfree)<<std::endl;     }     else     {       /*还需要处理回收其他空闲freelist里面的空间*/       result = NULL;     }     return(result);   };   template <class T>   void* MyAlloc<T>::refill(int num,int n)   {     int counts = num;     int *nobjs = &counts;     char* chunk;     Obj** my_free_list;     Obj* result;     Obj* current_obj;     Obj* next_obj;     int i;     chunk = chunk_alloc(n, nobjs);     if(chunk == NULL)     {       return(chunk);     }     counts = *nobjs;     if (1 == counts)     {       return(chunk);     }     my_free_list = pHead->uFreelist + freelist_index(n);     result = (Obj*)chunk;     *my_free_list = next_obj = (Obj*)(chunk + n*num);     for (i = 1; ; i++)     {       current_obj = next_obj;       next_obj = (Obj*)((char*)next_obj + n);       if (counts - 1 == i)       {         current_obj->M_free_list_link = 0;         break;       }       else       {         current_obj->M_free_list_link = next_obj;       }     }     return(result);   }; /*这个函数可以改写成自己的共享内存分配函数*/   static void InitShm()   {     int i,size=1000;     pHead = (Cookie*)malloc(sizeof(Cookie)+size);     pHead->iTotalsize = sizeof(Cookie)+size;     pHead->pStartall  = pHead;     pHead->pStartfree = (char*)pHead + sizeof(Cookie);     pHead->pEndfree   = (char*)pHead + pHead->iTotalsize;     for(i=0 ; i <NODENUMS ; i++)     {       pHead->sFreelistIndex[i]=0;       pHead->uFreelist[i]=0;       pHead->iUseNum[i]=0;     }   }   static void PrintFreelistAndCookie()   {     int i,j;     Obj* my_free_list;     std::cout<<"Cookie info :"<<std::endl;     std::cout<<"sizeof(struct Cookie) = "<<sizeof(Cookie)<<std::endl;     std::cout<<"Totalsize     = "<<pHead->iTotalsize<<std::endl;     std::cout<<"UsedSize      = "<<int(pHead->pStartfree-(char*)pHead)<<std::endl;     std::cout<<"FreepoolSize  = "<<int(pHead->pEndfree - pHead->pStartfree)<<std::endl;     std::cout<<"Startall      = "<<&(pHead->pStartall)<<std::endl;     std::cout<<"Startfree     = "<<&(pHead->pStartfree)<<std::endl;     std::cout<<"Endfree       = "<<&(pHead->pEndfree)<<std::endl;     std::cout<<"nFreelist info :"<<std::endl;     for(i=0 ; i<NODENUMS ; i++)     {       j=0;       std::cout<<"iUseNum["<<i<<"] = "<<pHead->iUseNum[i]<<std::endl;       std::cout<<"FreelistIndex["<<i<<"] = "<<pHead->sFreelistIndex[i]<<std::endl;       my_free_list = pHead->uFreelist[i];       if(my_free_list->M_client_data != 0)       {         while(my_free_list->M_client_data != 0)         {           j++;           my_free_list = my_free_list->M_free_list_link;         }         std::cout<<"free_list["<<i<<"]; node counts="<<j<<std::endl;       }     }   }   template <class T1, class T2>   bool operator== (const MyAlloc<T1>&,const MyAlloc<T2>&) throw()    {     return true;   }   template <class T1, class T2>   bool operator!= (const MyAlloc<T1>&,const MyAlloc<T2>&) throw()    {     return false;   } } #endif /*MY_ALLOCATOR_H_*/ 测试程序的源码如下： // MyStl.cpp : 定义控制台应用程序的入口点。 // #include "stdafx.h" #include <map> #include <vector> #include <string> #include <utility> #include <iostream> #include "MyAlloc.h" using namespace std; int _tmain(int argc, _TCHAR* argv[]) {   happyever ::InitShm();   multimap<string,int,less<string>,happyever ::MyAlloc<string> > m;   m.insert(make_pair(string("Harry"), 32));   m.insert(make_pair(string("Mary"), 59));   m.insert(make_pair(string("Roger"), 18));   m.insert(make_pair(string("Nancy"), 37));   m.insert(make_pair(string("Mary"), 23));      typedef multimap<string,int,less<string>,happyever ::MyAlloc<string> >::iterator Iter;   for (Iter p = m.begin(); p != m.end(); p++)   {     cout << p->first << "," << p->second << endl;   }   Iter p = m.find("Harry");   m.erase(p);   /*p = m.find("Harry");   cout << "Harry is: " << p->second << "." << endl;*/   for (Iter p = m.begin(); p != m.end(); p++)   {     cout << p->first << "," << p->second << endl;   }      return 0; }

以上程序在vs2005， vc6上测试通过。使用MinGW编译的时候只需要去掉 vc的预编译头文件
#include "stdafx.h"

　　即可。

　　以上程序只要稍微修改，就可以实现共享内存的管理，可以方便的使用标准库提供的容器。加上信号量的锁机制。

　　以上为了学习而改写的SGI的stl二级分配算法实现的。以上代码存在一定的局限性。我另外完整实现了共享内存管理的STL标准的alloctor程序，使用posix信号量加锁。目前应用在aix的xlC编译环境下。因为源码涉及公司的商业秘密，所以不能公开。但基本上以上源码已经体现了自己管理内存的完整思路，供这方面需求的朋友一起学习研究用