我是linux编程的新手,试图实现简单的msg队列工作。 但得到错误说消息很长,下面是我的代码,请建议是否有任何更正。
我知道类似的问题被多次询问,但我无法找到我的问题的解决方案,因此发布了代码。
#include <stdio.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <mqueue.h>
#include <stdlib.h>
#include <ctype.h>
#include <errno.h>
void* producerThRoutine (void *arg);
void* ConsumerThRoutine (void *arg);
int main()
{
int retVal = 0;
pthread_t producerThId,consumerThID;
mqd_t myMQdes;
struct mq_attr attr;
attr.mq_flags = 0;
attr.mq_maxmsg = 1024;
attr.mq_msgsize = 10;
attr.mq_curmsgs = 0;
myMQdes = mq_open("/myMessageQueue",O_CREAT | O_RDWR,S_IWUSR | S_IRUSR,&attr);
if(myMQdes == (mqd_t) -1){
perror("Message Queue creation failed\n");
exit(EXIT_FAILURE);
}
retVal = pthread_create(&producerThId,NULL,producerThRoutine,&myMQdes);
if(retVal != 0){
perror("\n producerThRoutine creation failed \n");
exit(EXIT_FAILURE);
}
retVal = pthread_create(&consumerThID,NULL,ConsumerThRoutine,&myMQdes);
if(retVal != 0){
perror("\n ConsumerThRoutine creation failed \n");
exit(EXIT_FAILURE);
}
retVal = pthread_join(producerThId,NULL);
if(retVal != 0){
perror("\n pthread_join for producer thread failed \n");
exit(EXIT_FAILURE);
}
retVal = pthread_join(consumerThID,NULL);
if(retVal != 0){
perror("\n pthread_join for consumer thread failed \n");
exit(EXIT_FAILURE);
}
mq_close(myMQdes);
mq_unlink("/myMessageQueue");
return 0;
}
void* producerThRoutine (void *arg)
{
char c;
char EOS = '\0';
int retVal;
mqd_t *pMQDes = (mqd_t *) arg;
printf("Enter the string you want to convert to upper case \n");
while( (c=getchar()) != EOF ){
if(c == '\n'){
retVal = mq_send( (*pMQDes),&EOS,sizeof(char),1);
if(retVal != 0){
perror("sending EOS to queue failed \n");
exit(EXIT_FAILURE);
}
break;
}
retVal = mq_send( (*pMQDes),&EOS,sizeof(char),1);
if(retVal != 0){
perror("sending character to queue failed \n");
break ;
}
}
}
void* ConsumerThRoutine (void *arg)
{
char msg;
int msg_priority,retVal;
mqd_t *pMQDes = (mqd_t *) arg;
while(1){
printf("\nthe converted string is : ");
retVal = mq_receive(* pMQDes,&amp; msg,sizeof(char),&amp; msg_priority);
if(retVal == -1){
perror("mq_receive failed");
exit(EXIT_FAILURE);
}
if( msg == '\0')
{
break;
}
putchar(toupper(msg));
}
}
答案 0 :(得分:1)
我刚刚查看了mq_receive的手册页,其中一个错误显示如下:
EMSGSIZE
msg_len was less than the mq_msgsize attribute of the message queue.
我改变了
retVal = mq_receive (*pMQDes,&msg,sizeof(char),&msg_priority);
到
retVal = mq_receive (*pMQDes,&msg,1024 * sizeof(char),&msg_priority);
其中1024是您设置的mq_msgsize。然后错误就消失了。