UNIX环境高级编程学习之第十五章进程间通信 - 两个进程通过映射普通文件实现共享内存通信

/* User:Lixiujie
* Date:20100831
* Desc:两个进程通过映射普通文件实现共享内存通信 写数据进程
* File:map1.c
* System:Ubuntu 64bit
* gcc map1.c -o mapDemo1
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
typedef struct _People{
char szName[32];
int  iAge;
}People;
int main(void){
int fd, i;
People *p;
char c = 'a';
/* 创建或打开一个空文件 */
fd = open("map.date", O_CREAT|O_RDWR|O_TRUNC, 00777);
if (-1 == fd){
perror("main() open() is failed!/n");
exit(1);
}
/* 产生空洞 */
if (lseek(fd, sizeof(People)*5-1, SEEK_SET) == -1){
perror("main() lseek() is failed!/n");
close(fd);
exit(1);
}
write(fd, "", 1);
/* 映射文件创建共享内存 */
p = (People *)mmap(NULL, sizeof(People)*10, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
if (MAP_FAILED == p){
perror("main() mmap() is failed!/n");
close(fd);
exit(1);
}
close(fd);
/* 写入数据, 写入数据是文件大小的2倍，
* 又因为没有超过超过文件大小整内存页大小，所以不会报错
* 否则 会收到SIGBUS信号
*/
for (i=0;i<10;i++){
(*(p+i)).szName[0] = c+i;
(*(p+i)).szName[1] = '/0';
(*(p+i)).iAge = 20 + i;
}
printf("main() map has data./n");
sleep(20);
/* 会把数据写入文件，删除共享内存 */
munmap(p, sizeof(People)*10);
printf("main() munmap() ok /n");
/* 此时再过会打开 读共享内存程序只有文件大小的数据。 */
return 0;
}

/* User:Lixiujie
* Date:20100831
* Desc:两个进程通过映射普通文件实现共享内存通信 读数据进程
* File:map2.c
* System:Ubuntu 64bit
* gcc map2.c -o mapDemo2
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
typedef struct _People{
char szName[32];
int  iAge;
}People;
int main(void){
int fd, i;
People *p;
/*打开一个文件 */
fd = open("map.date", O_CREAT|O_RDWR, 00777);
if (-1 == fd){
perror("main() open() is failed!/n");
exit(1);
}
p = (People*)mmap(NULL,sizeof(People)*10,PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
if (MAP_FAILED == p){
perror("main() mmap() is failed!/n");
close(fd);
exit(1);
}
close(fd);
for (i=0;i<10;i++){
printf("Name=%s, Age=%d/n",(*(p+i)).szName, (*(p+i)).iAge);
}
munmap(p, sizeof(People)*10);
return 0;
}