邮箱是操作系统中，一个进程给另一个进程发送消息的方式。在裸奔的单片机中，在两个函数中交换信息的时候，我们通常选择最简便的方式-全局变量，这种编程模式无疑是降低了安全性和可靠性。再且，邮箱还能起到挂起线程的作用。
本实验中创建一个邮箱，两个线程，线程2以一定周期发送邮箱，线程1以一定周期从邮箱中取出邮件。当线程2中发送20封邮件之后，发送一封特殊的邮件通知其他线程，自己已经运行结束。线程1取出邮件后，检查邮件是否是特殊邮件，如果是，则线程1也退出。
程序：
#include <rtthread.h>
void rt_init_thread_entry(void *parameter)
{
}
static struct rt_mailbox mb;
static rt_uint8_t mb_pool[128];
static rt_uint8_t mb_str1[] = "I'm a mail!";
static rt_uint8_t mb_str2[] = "This is another mail!";
static rt_uint8_t mb_str3[] = "Over!";
static rt_uint8_t thread1_stack[1024];
struct rt_thread thread1;
static void thread1_entry(void *parameter)
{
char *str;
while (1)
{
rt_kprintf("thread1: try to receive a mail.\n");
/* receive a mail from the mailbox. */
if (rt_mb_recv(&mb, (rt_uint32_t *)&str, RT_WAITING_FOREVER) == RT_EOK)
{
rt_kprintf("thread1: get a mail from mailbox.\n");
if (str == mb_str3)
break;
rt_thread_delay(10);
}
}
rt_mb_detach(&mb);
}
static rt_uint8_t thread2_stack[1024];
struct rt_thread thread2;
static void thread2_entry(void *parameter)
{
rt_uint8_t count;
count = 0;
while (count < 10)
{
count++;
if (count & 0x01)
{
rt_mb_send(&mb, (rt_uint32_t)&mb_str1[0]);
}
else
{
rt_mb_send(&mb, (rt_uint32_t)&mb_str2[0]);
}
rt_thread_delay(20);
}
rt_mb_send(&mb, (rt_uint32_t)&mb_str3[0]);
}
int rt_application_init()
{
rt_thread_t init_thread;
rt_err_t result;
result = rt_mb_init(&mb,
"mbt",
&mb_pool[0], sizeof(mb_pool)/4,
RT_IPC_FLAG_FIFO);
if (result != RT_EOK)
{
rt_kprintf("init mailbox failed.\n");
return -1;
}
init_thread = rt_thread_create("init",
rt_init_thread_entry, RT_NULL,
2048,
8, 20);
if (init_thread != RT_NULL)
rt_thread_startup(init_thread);
rt_thread_init(&thread1,
"thread1",
thread1_entry,
RT_NULL,
&thread1_stack[0],
sizeof(thread1_stack),10,5);
rt_thread_startup(&thread1);
rt_thread_init(&thread2,
"thread2",
thread2_entry,
RT_NULL,
&thread2_stack[0],
sizeof(thread2_stack),10,5);
rt_thread_startup(&thread2);
return 0;
}结果
thread1: try to recv a mail thread1: get a mail from mailbox, the content:I'm a mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:this is another mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:I'm a mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:this is another mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:I'm a mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:this is another mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:I'm a mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:this is another mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:I'm a mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:this is another mail! thread1: try to recv a mail thread1: get a mail from mailbox, the content:over