用信号量解决生产者消费者问题:
ipc.h
#ifndef _IPC_H_
#define _IPC_H_
#include <sys/types.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ERR_EXIT(m) \
do \
{ \
perror(m); \
exit(EXIT_FAILURE); \
} while(0)
union semun {
int val; /* value for SETVAL */
struct semid_ds *buf; /* buffer for IPC_STAT, IPC_SET */
unsigned short *array; /* array for GETALL, SETALL */
/* Linux specific part: */
struct seminfo *__buf; /* buffer for IPC_INFO */
};
int sem_create(key_t key);
int sem_open(key_t key);
int sem_p(int semid);
int sem_v(int semid);
int sem_d(int semid);
int sem_setval(int semid, int val);
int sem_getval(int semid);
int sem_getmode(int semid);
int sem_setmode(int semid,char* mode);
#endif /* _IPC_H_ */
ipc.c
#include "ipc.h"
int sem_create(key_t key)
{
int semid = semget(key, 1, 0666 | IPC_CREAT | IPC_EXCL);
if (semid == -1)
ERR_EXIT("semget");
return semid;
}
int sem_open(key_t key)
{
int semid = semget(key, 0, 0);
if (semid == -1)
ERR_EXIT("semget");
return semid;
}
int sem_p(int semid)
{
struct sembuf sb = {0, -1, 0};
int ret = semop(semid, &sb, 1);
if (ret == -1)
ERR_EXIT("semop");
return ret;
}
int sem_v(int semid)
{
struct sembuf sb = {0, 1, 0};
int ret = semop(semid, &sb, 1);
if (ret == -1)
ERR_EXIT("semop");
return ret;
}
int sem_d(int semid)
{
int ret = semctl(semid, 0, IPC_RMID, 0);
/*
if (ret == -1)
ERR_EXIT("semctl");
*/
return ret;
}
int sem_setval(int semid, int val)
{
union semun su;
su.val = val;
int ret = semctl(semid, 0, SETVAL, su);
if (ret == -1)
ERR_EXIT("semctl");
//printf("value updated...\n");
return ret;
}
int sem_getval(int semid)
{
int ret = semctl(semid, 0, GETVAL, 0);
if (ret == -1)
ERR_EXIT("semctl");
//printf("current val is %d\n", ret);
return ret;
}
int sem_getmode(int semid)
{
union semun su;
struct semid_ds sem;
su.buf = &sem;
int ret = semctl(semid, 0, IPC_STAT, su);
if (ret == -1)
ERR_EXIT("semctl");
printf("current permissions is %o\n",su.buf->sem_perm.mode);
return ret;
}
int sem_setmode(int semid,char* mode)
{
union semun su;
struct semid_ds sem;
su.buf = &sem;
int ret = semctl(semid, 0, IPC_STAT, su);
if (ret == -1)
ERR_EXIT("semctl");
printf("current permissions is %o\n",su.buf->sem_perm.mode);
sscanf(mode, "%o", (unsigned int*)&su.buf->sem_perm.mode);
ret = semctl(semid, 0, IPC_SET, su);
if (ret == -1)
ERR_EXIT("semctl");
printf("permissions updated...\n");
return ret;
}
sshfifo.h
#ifndef _SHM_FIFO_H_
#define _SHM_FIFO_H_
#include "ipc.h"
typedef struct shmfifo shmfifo_t;
typedef struct shmhead shmhead_t;
struct shmhead
{
unsigned int blksize;
// 块大小
unsigned int blocks;
// 总块数
unsigned int rd_index;
// 读索引
unsigned int wr_index;
// 写索引
};
struct shmfifo
{
shmhead_t *p_shm;
// 共享内存头部指针
char *p_payload;
// 有效负载的起始地址
int shmid;
// 共享内存ID
int sem_mutex;
// 用来互斥用的信号量
int sem_full;
// 用来控制共享内存是否满的信号量
int sem_empty;
// 用来控制共享内存是否空的信号量
};
shmfifo_t* shmfifo_init(int key, int blksize, int blocks);
void shmfifo_put(shmfifo_t *fifo, const void *buf);
void shmfifo_get(shmfifo_t *fifo, void *buf);
void shmfifo_destroy(shmfifo_t *fifo);
#endif /* _SHM_FIFO_H_ */
sshfifo.c
#include "shmfifo.h"
#include <assert.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));
int shmid;
shmid = shmget(key, 0, 0);
int size = sizeof(shmhead_t) + blksize*blocks;
if (shmid == -1)
{
fifo->shmid = shmget(key, size, IPC_CREAT | 0666);
if (fifo->shmid == -1)
ERR_EXIT("shmget");
fifo->p_shm = (shmhead_t*)shmat(fifo->shmid, NULL, 0);
if (fifo->p_shm == (shmhead_t*)-1)
ERR_EXIT("shmat");
fifo->p_payload = (char*)(fifo->p_shm + 1);
fifo->p_shm->blksize = blksize;
fifo->p_shm->blocks = blocks;
fifo->p_shm->rd_index = 0;
fifo->p_shm->wr_index = 0;
fifo->sem_mutex = sem_create(key);
fifo->sem_full = sem_create(key+1);
fifo->sem_empty = sem_create(key+2);
sem_setval(fifo->sem_mutex, 1);
sem_setval(fifo->sem_full, blocks);
sem_setval(fifo->sem_empty, 0);
}
else
{
fifo->shmid = shmid;
fifo->p_shm = (shmhead_t*)shmat(fifo->shmid, NULL, 0);
if (fifo->p_shm == (shmhead_t*)-1)
ERR_EXIT("shmat");
fifo->p_payload = (char*)(fifo->p_shm + 1);
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);
memcpy(fifo->p_payload+fifo->p_shm->blksize*fifo->p_shm->wr_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);
memcpy(buf, fifo->p_payload+fifo->p_shm->blksize*fifo->p_shm->rd_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_d(fifo->sem_mutex);
sem_d(fifo->sem_full);
sem_d(fifo->sem_empty);
shmdt(fifo->p_shm);
shmctl(fifo->shmid, IPC_RMID, 0);
free(fifo);
}
ssmfifo_free.c
#include "shmfifo.h"
typedef struct stu
{
char name[32];
int age;
} STU;
int main(void)
{
shmfifo_t *fifo = shmfifo_init(1234, sizeof(STU), 3);
shmfifo_destroy(fifo);
return 0;
}
shmfifo_recv.c
#include "shmfifo.h"
typedef struct stu
{
char name[32];
int age;
} STU;
int main(void)
{
shmfifo_t *fifo = shmfifo_init(1234, sizeof(STU), 3);
STU s;
memset(&s, 0, sizeof(STU));
int i;
for (i=0; i<5; i++)
{
shmfifo_get(fifo, &s);
printf("name = %s age = %d\n", s.name, s.age);
}
return 0;
}
shmfifo_send.c
#include "shmfifo.h"
typedef struct stu
{
char name[32];
int age;
} STU;
int main(void)
{
shmfifo_t *fifo = shmfifo_init(1234, sizeof(STU), 3);
STU s;
memset(&s, 0, sizeof(STU));
s.name[0]=‘A‘;
int i;
for (i=0; i<5; i++)
{
s.age = 20 +i;
shmfifo_put(fifo, &s);
s.name[0] = s.name[0] + 1;
printf("send ok\n");
}
return 0;
}