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        作者:黑客防线网安C/C++教程基地 来源:黑客防线网安C/C++教程基地 浏览次数:0 | 
  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:
#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"
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