core/thread/mbox.c

   1 /*
   2  * mbox.c
   3  *
   4  * Simple thread mailbox interface
   5  */
   6
   7 #include "thread.h"
   8 #include "mbox.h"
   9 #include <errno.h>
  10
  11 void mbox_init(struct mailbox *mbox, size_t size)
  12 {
  13     if (!!mbox) {
  14         sem_init(&mbox->prod_sem, size); /* All slots empty */
  15         sem_init(&mbox->cons_sem, 0);    /* No slots full */
  16         sem_init(&mbox->head_sem, 1);    /* Head mutex */
  17         sem_init(&mbox->tail_sem, 1);    /* Tail mutex */
  18
  19         mbox->wrap = &mbox->data[size];
  20         mbox->head = &mbox->data[0];
  21         mbox->tail = &mbox->data[0];
  22     }
  23 };
  24
  25 int mbox_post(struct mailbox *mbox, void *msg, mstime_t timeout)
  26 {
  27     if (!mbox_is_valid(mbox))
  28         return ENOMEM;
  29     if (sem_down(&mbox->prod_sem, timeout) == (mstime_t)-1)
  30         return ENOMEM;
  31     sem_down(&mbox->head_sem, 0);
  32
  33     *mbox->head = msg;
  34     mbox->head++;
  35     if (mbox->head == mbox->wrap)
  36         mbox->head = &mbox->data[0];
  37
  38     sem_up(&mbox->head_sem);
  39     sem_up(&mbox->cons_sem);
  40     return 0;
  41 }
  42
  43 mstime_t mbox_fetch(struct mailbox *mbox, void **msg, mstime_t timeout)
  44 {
  45     mstime_t t;
  46
  47     if (!mbox)
  48         return -1;
  49     t = sem_down(&mbox->cons_sem, timeout);
  50     if (t == (mstime_t)-1)
  51         return -1;
  52     t += sem_down(&mbox->tail_sem, 0);
  53
  54     if (msg)
  55         *msg = *mbox->tail;
  56     mbox->tail++;
  57     if (mbox->tail == mbox->wrap)
  58         mbox->tail = &mbox->data[0];
  59
  60     sem_up(&mbox->tail_sem);
  61     sem_up(&mbox->prod_sem);
  62     return t;
  63 }