RTAI的用户空间编程（六）——管道通讯

包含头文件#include “rtai_sched.h”
1. 发送函数

int rt_mbx_send (MBX* mbx, void* msg, int msg_size);//无条件发送消息int rt_mbx_send_wp (MBX* mbx, void* msg, int msg_size); //在不阻塞当期调用的任务的情况下，尽可能多的发送数据。消息长度是msg_size。int rt_mbx_send_if (MBX* mbx, void* msg, int msg_size); //发送一个消息, 要求在不阻塞当前调用任务的情况下，整个消息可以完整传递。int rt_mbx_send_until (MBX* mbx, void* msg, int msg_size, RTIME time);int rt_mbx_send_timed (MBX* mbx, void* msg, int msg_size, RTIME delay);//rt_mbx_send_until和rt_mbx_send_timed发送消息msg_size大小的msg到邮箱mbx。调用者将被阻塞,直到所有字节的入消息队列、超时过期或发生错误。

函数返回
成功,未寄出的字节的数量被返回；失败，返回负值，负值定义如下：EINVAL mbx指向无效的mailbox（mbx points to not a valid mailbox）.

2. 接收函数

int rt_mbx_receive (MBX* mbx, void* msg, int msg_size);//无条件接受消息int rt_mbx_receive_wp (MBX* mbx, void* msg, int msg_size);//在不阻塞当期调用的任务的情况下，尽可能多的接收数据。int rt_mbx_receive_if (MBX* mbx, void* msg, int msg_size);//整个msg_size大小的消息能立刻获取到时，接收消息。int rt_mbx_receive_until (MBX* mbx, void* msg, int msg_size, RTIME time);int rt_mbx_receive_timed (MBX* mbx, void* msg, int msg_size, RTIME delay);//调用者将被阻塞,直到所有字节的入消息队列、超时过期或发生错误。time是绝对值，Delay是相对于当前时间的相对值.

函数返回
成功，返回收到的字节数量。
失败，返回一个负值，定义如下：EINVAL mbx指向无效的mailbox（mbx points to not a valid mailbox）.

3. 示例代码

/* messqueue.c*//* ------------ headers ------------------------------------------- */#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <string.h>#include <sys/types.h>#include <sys/mman.h>#include <sys/stat.h>#include <fcntl.h>#include <sched.h>#include <linux/errno.h> /* error codes */#include <signal.h>#include <pthread.h>#include <rtai_lxrt.h>#include <rtai_mbx.h>#include <rtai_msg.h>/* ------------ globals ------------------------------------------- *//* turn on(1) or off(0) debugging */const int DEBUG=1;// fix include warning//#include <asm/system.h>//#include <rtai_posix.h>int pthread_cancel_rt(pthread_t thread);// linux threads id'sstatic int thread1;static int thread2;// realtime task structuresstatic RT_TASK  *t1;static RT_TASK  *t2;// message queuestatic MBX *mesgQueueId;#define MAX_MESSAGES 100#define MAX_MESSAGE_LENGTH 50/* ------------ functions ------------------------------------------- */void taskOne(void *arg){    int retval;    char message[] = "Received message from taskOne";    /*  make this thread LXRT soft realtime */    t1 = rt_task_init_schmod(nam2num("TASK1"), 0, 0, 0, SCHED_FIFO, 0xF);    mlockall(MCL_CURRENT | MCL_FUTURE);    // makes task hard real time (only when not developing/debugging)    if ( !DEBUG )  rt_make_hard_real_time();    rt_printk("Started taskOne\n");       /* send message */    retval = rt_mbx_send(mesgQueueId, message, sizeof(message));    if (0 != retval) {        if (-EINVAL == retval) {          rt_printk("mailbox is invalid\n");        } else {          /* unknown error */          rt_printk("Unknown mailbox error\n");        }    }}void taskTwo(void *arg){    int retval;    char msgBuf[MAX_MESSAGE_LENGTH];    /*  make this thread LXRT soft realtime */    t2 = rt_task_init_schmod(nam2num("TASK2"), 0, 0, 0, SCHED_FIFO, 0xF);    mlockall(MCL_CURRENT | MCL_FUTURE);    // makes task hard real time (only when not developing/debugging)    if ( !DEBUG )  rt_make_hard_real_time();    rt_printk("Started taskTwo\n");    /* receive message */    retval = rt_mbx_receive_wp(mesgQueueId, msgBuf, 50);    if (-EINVAL == retval) {          rt_printk("mailbox is invalid\n");    } else {        rt_printk("message length=50-%d\n",retval);        rt_printk("message : %s\n",msgBuf);     }}void cleanup(void){    /* delete message queue */          rt_mbx_delete(mesgQueueId);    // task end themselves -> not necesssary to delete them     return;}/* ------------ main ------------------------------------------- */int main(void){       printf("Start of main\n");    /*  make this thread LXRT soft realtime */    rt_task_init_schmod(nam2num("TASK0"), 0, 0, 0, SCHED_FIFO, 0xF);    mlockall(MCL_CURRENT | MCL_FUTURE);    // set realtime timer to run in oneshot mode        rt_set_oneshot_mode();    // start realtime timer and scheduler    start_rt_timer(1);    /* create message queue */        mesgQueueId = rt_typed_mbx_init (nam2num("MSGQUEUE"), MAX_MESSAGES, FIFO_Q);    if (mesgQueueId  == 0) {        printf("Error creating message queue\n");        return 1;    }    // create the linux threads     thread1 = rt_thread_create(taskOne, NULL, 10000);    thread2 = rt_thread_create(taskTwo, NULL, 10000);    // wait for end of program    printf("TYPE <ENTER> TO TERMINATE\n");    getchar();    // cleanup    cleanup();    printf("Finished\n");        return 0;}