內存池管理程序源碼如下
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; /* 共享內存鍵值 */ int iShmID; /* iShmKey對應的shmid */ int iSemKey; /* 鎖信號鍵值 */ int iSemID; /* 鎖信號標識 */ int iTotalsize; /* 容器總容量 */ void* pStartall; /* 共享內存自身地址 */ char* pStartfree; /* 自由空間的開始地址*/ char* pEndfree; /* 自由空間的結束地址*/ int iUseNum[NODENUMS]; /*用來存放free_list中節點的size*/ short sFreelistIndex[NODENUMS]; /*存放分配內存節點的鏈表*/ 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); /*這個地方可能會有問題*/ //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 { /*還需要處理回收其他空閒freelist裡面的空間*/ 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); }; /*這個函數可以改寫成自己的共享內存分配函數*/ 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_*/ 測試程序的源碼如下： // MyStl.cpp : 定義控制台應用程序的入口點。Tw.wiNGWit.Com // #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上測試通過。使用MinGW編譯的時候只需要去掉vc的預編譯頭文件 #include "stdafx.h"
即可。
以上程序只要稍微修改，就可以實現共享內存的管理，可以方便的使用標准庫提供的容器。加上信號量的鎖機制。
以上為了學習而改寫的SGI的stl二級分配算法實現的。以上代碼存在一定的局限性。我另外完整實現了共享內存管理的STL標准的alloctor程序，使用posix信號量加鎖。目前應用在aix的xlC編譯環境下。因為源碼涉及公司的商業秘密，所以不能公開。但基本上以上源碼已經體現了自己管理內存的完整思路，供這方面需求的朋友一起學習研究用。
