利用linux下的文件内存映射可以实现进程共享数据,我们可以把一个文件映射到虚拟内存中使多个进程进行共享,
到这里我们大概能想到他能应用到的领域 是很广泛的
主要涉及到 mmap munmap msync 三个函数的应用
下面贴代码
下面一段代码是为文件建立一个简单的记录存储,并且通过内存映射修改文件内容
/*************************************************************************> File Name: memdb.c> Author: > Mail: > Created Time: Fri 13 Feb 2015 03:46:11 AM PST ************************************************************************/#include<stdio.h>#include<sys/mman.h>#include<stdlib.h>#include<string.h>#include<unistd.h>#include<sys/types.h>#include<sys/stat.h>#include<fcntl.h>#define RECORD_NUM 100#define DATA_FILE "./db.dat"//定义数据记录typedef struct { int index ; char str[20];}RecordData;int main(){FILE*pFile ;void*pMap=NULL;int fdFIle;int i;RecordData record,*pMappedRecord;pFile=fopen(DATA_FILE,"w+") ;if(pFile==NULL){printf("Create File Error\n") ;return 0;} for(i=0;i<RECORD_NUM;i++) {record.index=i ;sprintf(record.str,"Record:%d",i);fwrite((void*)&record,sizeof(record),1,pFile); } fclose(pFile) ; fdFIle =open(DATA_FILE,O_RDWR) ;if(fdFIle==-1){printf("Open DataFile Error!\n");return 0 ;}//map file to memory from file offset 0 to endpMap=mmap(NULL,sizeof(RecordData)*RECORD_NUM,PROT_READ|PROT_WRITE,MAP_SHARED,fdFIle,0) ;if(pMap==MAP_FAILED){printf("Map file to Virtual Memory Error!\n");close(fdFIle);return 0;}///get thirty recordpMappedRecord=(struct RecordData*)pMap ;printf("%d:%s\n",pMappedRecord[29].index,pMappedRecord[29].str);//modify thirty datasprintf(pMappedRecord[29].str,"%s","Hello,Usher");//update mapped memory info to filemsync(pMap,sizeof(RecordData)*RECORD_NUM,MS_ASYNC);munmap(pMap,sizeof(RecordData)*RECORD_NUM);}<span style="font-family: Arial, Helvetica, sans-serif; font-size: 12px;">我们在另一个进程中可以通过程序查看共享文件内容</span></pre><pre code_snippet_id="604510" snippet_file_name="blog_20150213_6_8975773" name="code" class="cpp">/*************************************************************************> File Name: memdb.c> Author: > Mail: > Created Time: Fri 13 Feb 2015 03:46:11 AM PST ************************************************************************/#include<stdio.h>#include<sys/mman.h>#include<stdlib.h>#include<string.h>#include<unistd.h>#include<sys/types.h>#include<sys/stat.h>#include<fcntl.h>#define RECORD_NUM 100#define DATA_FILE "./db.dat"//定义数据记录typedef struct { int index ; char str[20];}RecordData;int main(){int i;void*pMap=NULL;int fdFIle;RecordData record,*pMappedRecord;fdFIle =open(DATA_FILE,O_RDWR) ;if(fdFIle==-1){printf("Open DataFile Error!\n");return 0 ;}//map file to memory from file offset 0 to endpMap=mmap(NULL,sizeof(RecordData)*RECORD_NUM,PROT_READ|PROT_WRITE,MAP_SHARED,fdFIle,0) ;if(pMap==MAP_FAILED){printf("Map file to Virtual Memory Error!\n");close(fdFIle);return 0;}///get thirty recordpMappedRecord=(struct RecordData*)pMap ;for(i=0;i<RECORD_NUM;i++)printf("%d:%s\n",pMappedRecord[i].index,pMappedRecord[i].str);munmap(pMap,sizeof(RecordData)*RECORD_NUM);}
，代替你主持夕阳的葬礼。
