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/*
* mbox.c
*
* Simple thread mailbox interface
*/
#include "thread.h"
#include "mbox.h"
#include <errno.h>
void mbox_init(struct mailbox *mbox, size_t size)
{
if (!!mbox) {
sem_init(&mbox->prod_sem, size); /* All slots empty */
sem_init(&mbox->cons_sem, 0); /* No slots full */
sem_init(&mbox->head_sem, 1); /* Head mutex */
sem_init(&mbox->tail_sem, 1); /* Tail mutex */
mbox->wrap = &mbox->data[size];
mbox->head = &mbox->data[0];
mbox->tail = &mbox->data[0];
}
};
int mbox_post(struct mailbox *mbox, void *msg, mstime_t timeout)
{
if (!mbox_is_valid(mbox))
return ENOMEM;
if (sem_down(&mbox->prod_sem, timeout) == (mstime_t)-1)
return ENOMEM;
sem_down(&mbox->head_sem, 0);
*mbox->head = msg;
mbox->head++;
if (mbox->head == mbox->wrap)
mbox->head = &mbox->data[0];
sem_up(&mbox->head_sem);
sem_up(&mbox->cons_sem);
return 0;
}
mstime_t mbox_fetch(struct mailbox *mbox, void **msg, mstime_t timeout)
{
mstime_t t;
if (!mbox)
return -1;
t = sem_down(&mbox->cons_sem, timeout);
if (t == (mstime_t)-1)
return -1;
t += sem_down(&mbox->tail_sem, 0);
if (msg)
*msg = *mbox->tail;
mbox->tail++;
if (mbox->tail == mbox->wrap)
mbox->tail = &mbox->data[0];
sem_up(&mbox->tail_sem);
sem_up(&mbox->prod_sem);
return t;
}
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