linux-共享内存

//shm_consumer.c

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/shm.h>
#include "shm_com.h"


/*
	this file is the consumer process
*/

int main(){
	int running = 1;
	void * shared_memory = (void*)0;
	struct shared_use_st * shared_stuff;
	int shm_id;
	srand((unsigned int)getpid());
	/* 1. creat share memory */
	shm_id = shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT);
	if(-1 == shm_id){
		fprintf(stderr, "shmget failed\n"); exit(EXIT_FAILURE);	
	}
	/* 2. attach shared memory addredd in current process address space */
	shared_memory = shmat(shm_id, (void*)0, 0);
	if((void*)-1 == shared_memory){
		fprintf(stderr, "shmat failed\n"); exit(EXIT_FAILURE);	
	}
	/* 3. converse shared memory to struct shared_use_st*/
	shared_stuff = (struct shared_use_st*)shared_memory;
	shared_stuff->written_by_you = 0;
	/* should use other synchron system*/
	while(running){
		if(shared_stuff->written_by_you){
			printf("[Consumer says] You wrote:%s", shared_stuff->some_text );
			sleep(rand() % 4);
			shared_stuff->written_by_you = 0;
			if(strncmp(shared_stuff->some_text, "end", 3) == 0){
				running = 0;			
			}		
		}	
	}
	/* 4. detach shared memory*/
	if(shmdt(shared_memory) == -1){
		fprintf(stderr, "shmdt failed\n");
		exit(EXIT_FAILURE);	
	}
	/*5. delete shared memory , "shmctl" not "shmctrl"*/
	if(shmctl(shm_id, IPC_RMID, 0) ==-1){
	        fprintf(stderr, "shmctrl(IPC_RMID) failed\n");
		exit(EXIT_FAILURE);	
	}
	exit(EXIT_SUCCESS);
}

//shm_producer.c

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/shm.h>
#include "shm_com.h"


/*
	this file is the Producer process
*/

int main(){
	int running = 1;
	void * shared_memory = (void*)0;
	struct shared_use_st * shared_stuff;
	int shm_id;
	char some_text[128] = {0};
	srand((unsigned int)getpid());

	/* 1. creat share memory */
	shm_id = shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT);
	if(-1 == shm_id){
		fprintf(stderr, "shmget failed\n"); exit(EXIT_FAILURE);	
	}
	/* 2. attach shared memory addredd in current process address space */
	shared_memory = shmat(shm_id, (void*)0, 0);
	if((void*)-1 == shared_memory){
		fprintf(stderr, "shmat failed\n"); exit(EXIT_FAILURE);	
	}
	/* 3. converse shared memory to struct shared_use_st*/
	shared_stuff = (struct shared_use_st*)shared_memory;
	shared_stuff->written_by_you = 0;
	while(running){

		while(shared_stuff->written_by_you){
			printf("wait for consumer to read...\n");
			sleep(1);		
		}
		
		printf("[Producer]:Enter some text: ");
		fgets(some_text, 128, stdin);
		strncpy(shared_stuff->some_text, some_text, 128);
		shared_stuff->written_by_you = 1;
		if(strncmp(some_text, "end", 3) == 0){
			running = 0;			
		}		
			
	}
	/* 4. detach shared memory*/
	if(shmdt(shared_memory) == -1){
		fprintf(stderr, "shmdt failed\n");
		exit(EXIT_FAILURE);	
	}
	exit(EXIT_SUCCESS);
}