core/include/mbox.h

   1 /*
   2  * mbox.h
   3  *
   4  * Simple thread mailbox interface
   5  */
   6
   7 #ifndef _MBOX_H
   8 #define _MBOX_H
   9
  10 #include "thread.h"
  11
  12 /*
  13  * If a mailbox is allocated statically (as a struct mailbox), this
  14  * is the number of slots it gets.
  15  */
  16 #define MAILBOX_STATIC_SIZE     512
  17
  18 struct mailbox {
  19     struct semaphore prod_sem;  /* Producer semaphore (empty slots) */
  20     struct semaphore cons_sem;  /* Consumer semaphore (data slots) */
  21     struct semaphore head_sem;  /* Head pointer semaphore */
  22     struct semaphore tail_sem;  /* Tail pointer semaphore */
  23     void **wrap;                /* Where pointers wrap */
  24     void **head;                /* Head pointer */
  25     void **tail;                /* Tail pointer */
  26
  27     void *data[MAILBOX_STATIC_SIZE]; /* Data array */
  28 };
  29
  30 /* The number of bytes for an mailbox of size s */
  31 #define MBOX_BYTES(s) (sizeof(struct mailbox) + \
  32                        ((s)-MAILBOX_STATIC_SIZE)*sizeof(void *))
  33
  34 void mbox_init(struct mailbox *mbox, size_t size);
  35 int mbox_post(struct mailbox *mbox, void *msg, mstime_t timeout);
  36 mstime_t mbox_fetch(struct mailbox *mbox, void **msg, mstime_t timeout);
  37
  38 /*
  39  * This marks a mailbox object as unusable; it will remain unusable
  40  * until sem_init() is called on it again.  This DOES NOT clear the
  41  * list of blocked processes on this mailbox!
  42  *
  43  * It is also possible to mark the mailbox invalid by zeroing its
  44  * memory structure.
  45  */
  46 static inline void mbox_set_invalid(struct mailbox *mbox)
  47 {
  48     if (!!mbox)
  49         sem_set_invalid(&mbox->prod_sem);
  50 }
  51
  52 /*
  53  * Ask if a mailbox object has been initialized.
  54  */
  55 static inline bool mbox_is_valid(struct mailbox *mbox)
  56 {
  57     return ((!!mbox) && sem_is_valid(&mbox->prod_sem));
  58 }
  59
  60 #endif /* _MBOX_H */