windows下利用文件映射实现共享内存
windows下利用文件映射实现共享内存的办法比较简单，下面是实现代码，细节用注释说明．
调用类似linux下shm的操作．该类没有进行太多的测试，欢迎提出问题和bug～～：）
#include <windows.h>#include <string>#include <iostream>#include <assert.h>using std::string;using std::cout;using std::endl;#pragma warning(disable: 4311)class shareMemory{private: LPWSTR shm_name_u; bool is_create_file; void * sh_base; HANDLE semaphore; HANDLE file_mapping; int addr_len;public:/*create＿file用来说明是用磁盘文件映射还是页文件映射，如果用磁盘文件映射，共享内存不会出现存储器release后出现违规访问的问题，但是会在磁盘上建立一个文件，文件的名称由参数shm＿name给定．如果用页文件映射，则不会在磁盘上建立一个文件*/ shareMemory(const string& shm_name, bool create_file=false):is_create_file(create_file) { const char * _c_shm_name = shm_name.c_str(); int _size =(int)shm_name.length()+1; shm_name_u=(LPWSTR)malloc(_size*2); MultiByteToWideChar(CP_ACP,0,_c_shm_name,_size,shm_name_u,_size); semaphore = CreateSemaphore(NULL,1,1,NULL); sh_base = NULL; file_mapping = INVALID_HANDLE_VALUE; } void * shm_open(void* addr,const int length, DWORD protect) { addr_len = length; HANDLE _file_handle = INVALID_HANDLE_VALUE; if(is_create_file) { _file_handle= CreateFile(shm_name_u,GENERIC_READ|GENERIC_WRITE,0, NULL,OPEN_ALWAYS,FILE_ATTRIBUTE_NORMAL,0);#ifdef _DEBUG if(_file_handle==INVALID_HANDLE_VALUE) cout<<"can not create file! we use page file instead!";#endif //end _DEBUG }/*打开指定名称的文件映射，如果不存在则创建一个*/ file_mapping = OpenFileMapping(PAGE_READWRITE,false,shm_name_u ); if(file_mapping!=NULL) goto file_mapping_exist; file_mapping = CreateFileMapping(_file_handle,NULL,PAGE_READWRITE, 0,length,shm_name_u);#ifdef _DEBUG assert(file_mapping);#endif if(file_mapping==NULL) return NULL;file_mapping_exist: sh_base = MapViewOfFileEx(file_mapping,protect,0,0,length,addr); CloseHandle(_file_handle); return sh_base; } /*往共享内存中写数据，返回写出数据的字节个数*/ int shm_write(void *dest, void * src, int size) { if(!check_adress(dest)) return -1; int _write_count = (int)sh_base+addr_len - (int)dest; if(_write_count>size) _write_count = size;/*利用semaphore进行保护映射的区域（同一进程的不同线程调用时候才进行保护）*/ WaitForSingleObject(semaphore,INFINITE); memcpy(dest,src,_write_count); ReleaseSemaphore(semaphore,1,NULL); FlushViewOfFile(sh_base,_write_count); return _write_count; } /*从共享内存中读数据，返回读出的数据字节个数＊*/int shm_read(void* src, void * dest, int size) { if(!check_adress(src)) return -1; int _read_count = (int)sh_base+addr_len -(int) src; if(_read_count>size) _read_count = size; memcpy(dest,src,_read_count); return _read_count; } ~shareMemory() { UnmapViewOfFile(sh_base); free(shm_name_u); CloseHandle(semaphore); CloseHandle(file_mapping); }private :/*进行地址检测*/ bool check_adress(void* addr) { if( ( (int)addr <(int)sh_base) || ((int)addr > (int)sh_base+addr_len) ) { SetLastError(ERROR_ACCESS_DENIED);#ifdef _DEBUG printf("access denied,the destination address out of the map view!");#endif //_DEBUG return false; } return true; }};
测试：
写进程的主函数：
int main(){ shareMemory sm("boost", false); void * bs = sm.shm_open(NULL,1000*4,FILE_MAP_WRITE); if(bs==NULL) return -1; int a[10]; for(int i=0; i<10; ++i) a[i] = i; sm.shm_write(bs,a,10*4); Sleep(100000);}
读进程的主函数：
int main(){ shareMemory sm("boost", false); void * bs = sm.shm_open(NULL,1000,FILE_MAP_READ); if(bs==NULL) { cout<<"null"; return -1; } int b[10]; sm.shm_read(bs,b,10*4); for(int i=0; i<10; ++i) cout<<b[i]<<" ";}