MacOS 源自BSD。后者的手册明确指出,类似或对结果文件描述符的操作会返回read()错误write(): 在共享内存对象上或在 shm_open() 返回的描述符上使用 open(2)、read(2) 或 write(2) 的结果是未定义的。共享内存对象本身或其内容是否在重新启动后仍然存在也是未定义的。
通过使用适当的同步对象（其本身可能存在于共享内存中，尽管存在其他选项）来同步对共享内存的访问。@Andre...
int main(){ int fd;fd = shm_open("region", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);if (fd<0) { printf("error open region\n");return 0;} ftruncate(fd, 10);ptr = mmap(NULL, 10, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);if (ptr == MAP_FAILED) { printf("error ...
...mmap将句柄作为共享内存的底层支撑对象,映射到内存中,这样可以不通过read、write在进程之间共享内存。由此推测一下,在*nix的进程间传 递数据更加原始的方法是进程间读写一个文件。...所以想到了将这个文件 句柄映射到内存中,这样就提高了进程间传递数据的效率。 需要注意的函数 -- msync 当修改了...
ptr=mmap(NULL,100,PROT_READ|PROT_WRITE,MAP_SHARED,shm_id,0);/*第三步:连接共享内存区*/strcpy(ptr,"\0"); sem_wait(sem);/*第四步:申请信号量*/printf("server : %s\n",ptr);/*输入共享内存区内容*/strcpy(ptr,"\0");/*清空共享内存区*/sem_unlink(argv[1]);/*第五步:删除信号量*/...
{#ifdef_WIN32#ifndef_XBOXhMemoryMapping = CreateFileMapping(INVALID_HANDLE_VALUE,NULL, PAGE_READWRITE,0, (DWORD)(size),NULL); GetSystemInfo(&sysInfo);#endif#elifdefined(ANDROID)// Use ashmem so we don't have to allocate a file on disk!fd = ashmem_create_region("PPSSPP_RAM", size);...
h> int main(void) { // Open shared memory int fd = shm_open("TEST", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR); ftruncate(fd, sizeof(int)); // Map shared memory int *shm = mmap(NULL, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED, fd,0); close(fd); // Access shared...
char* map = mmap(NULL, length, PROT_READ | PROT_WRITE, MAP_SHARED, fd,0); if(map == MAP_FAILED) { perror("Error mmapping the file"); exit(EXIT_FAILURE); } // 打印映射的内存内容,即文件内容 for(off_t i =0; i < length; i++) { ...
created by ORing together exactly one ofO_RDONLYorO_RDWRand any of the other flags listed here:O_RDONLYOpen the object for read access. A shared memory object opened in this way can bemmap(2)ed only for read (PROT_READ) access.O_RDWROpen the object for read-write access.O_CREATCreate...
read.c #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> #include <sys/mman.h> #include <string.h> #include <errno.h> #include <unistd.h> /* int shm_open(const char *name, int oflag, mode_t mode); ...