shmfifo源代码(C语言版)

#include "shmfifo.h" shmfifo_t *shmfifo_init(int key, int blksize, int blocks) { shmfifo_t *fifo = (shmfifo_t *)malloc(sizeof(shmfifo_t)); assert(fifo != NULL); memset(fifo, 0, sizeof(shmfifo_t)); // 打开一块共享内存 int shmid = shmget(key, 0, 0); // 如果打开失败, 则表示该共享内存尚未创建, 则创建之 if (shmid == -1) { /** 设置共享内存 **/ int size = blksize*blocks + sizeof(shmhead_t); //创建共享内存 fifo->shmid = shmget(key, size, IPC_CREAT|0666); if (fifo->shmid == -1) err_exit("shmget error"); //创建共享内存成功, 则需要将其连接到进程的地址空间 //void *shmat(int shmid, const void *shmaddr, int shmflg); fifo->p_shm = (shmhead_t *)shmat(fifo->shmid, NULL, 0); if (fifo->p_shm == (void *) -1) err_exit("shmat error"); //将共享内存的首部初始化为struct shmhead fifo->p_shm->blksize = blksize; fifo->p_shm->blocks = blocks; fifo->p_shm->rd_index = 0; fifo->p_shm->wr_index = 0; fifo->p_payload = (char *)(fifo->p_shm+1); /** 设置三个信号量 **/ fifo->sem_mutex = sem_create(key); sem_setval(fifo->sem_mutex, 1); fifo->sem_full = sem_create(key+1); sem_setval(fifo->sem_full, blocks); fifo->sem_empty = sem_create(key+2); sem_setval(fifo->sem_empty, 0); } else { fifo->shmid = shmid; //共享内存已经存在, 并且打开成功, 则需要将其连接到进程的地址空间 fifo->p_shm = (shmhead_t *)shmat(fifo->shmid, NULL, 0); if (fifo->p_shm == (void *) -1) err_exit("shmat error"); fifo->p_payload = (char *)(fifo->p_shm+1); /** 设置三个信号量 **/ fifo->sem_mutex = sem_open(key); fifo->sem_full = sem_open(key+1); fifo->sem_empty = sem_open(key+2); } return fifo; } void shmfifo_put(shmfifo_t *fifo, const void *buf) { sem_P(fifo->sem_full); sem_P(fifo->sem_mutex); //从结构体中获取写入位置 char *index = fifo->p_payload + (fifo->p_shm->wr_index * fifo->p_shm->blksize); memcpy(index, buf, fifo->p_shm->blksize); fifo->p_shm->wr_index = (fifo->p_shm->wr_index+1)%fifo->p_shm->blocks; sem_V(fifo->sem_mutex); sem_V(fifo->sem_empty); } void shmfifo_get(shmfifo_t *fifo, void *buf) { sem_P(fifo->sem_empty); sem_P(fifo->sem_mutex); //从结构体中获取读出位置 char *index = fifo->p_payload + (fifo->p_shm->rd_index * fifo->p_shm->blksize); memcpy(buf, index, fifo->p_shm->blksize); fifo->p_shm->rd_index = (fifo->p_shm->rd_index+1)%fifo->p_shm->blocks; sem_V(fifo->sem_mutex); sem_V(fifo->sem_full); } void shmfifo_destroy(shmfifo_t *fifo) { sem_delete(fifo->sem_mutex); sem_delete(fifo->sem_full); sem_delete(fifo->sem_empty); shmdt(fifo->p_shm); if (shmctl(fifo->shmid, IPC_RMID, NULL) == -1) err_exit("remove share memory error"); free(fifo); }