ChibiOS/src/chmsg.c

/*
    ChibiOS/RT - Copyright (C) 2006-2007 Giovanni Di Sirio.

    This file is part of ChibiOS/RT.

    ChibiOS/RT is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS/RT is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @addtogroup Messages
 * @{
 */
#include <ch.h>

#ifdef CH_USE_MESSAGES
/**
 * Sends a message to the specified thread. The client is stopped until the
 * server executes a \p chMsgRelease() after receiving the message.
 *
 * @param tp the pointer to the thread
 * @param msg the message, it can be a pointer to a complex structure
 * @return the return message from \p chMsgRelease()
 */
t_msg chMsgSend(Thread *tp, t_msg msg) {

  chSysLock();

  fifo_insert(currp, &tp->p_msgqueue);
  if (tp->p_state == PRWTMSG)
    chSchReadyI(tp);
  currp->p_msg = msg;
  chSchGoSleepS(PRSNDMSG);
  msg = currp->p_rdymsg;

  chSysUnlock();
  return msg;
}

#ifdef CH_USE_MESSAGES_EVENT
/**
 * Sends a message to the specified thread and atomically triggers an event.
 * The client is stopped until the server executes a \p chMsgRelease()
 * after receiving the message.
 *
 * @param tp the pointer to the thread
 * @param msg the message, it can be a pointer to a complex structure
 * @param esp the event source to pulse while sending the message
 * @return the return message from \p chMsgRelease()
 * @return the message return status from \p chMsgRelease()
 * @note This function assumes that the receiving thread is not sleeping into
 *       a \p chMsgWait(). The use case is that the server thread is waiting
 *       for both messages AND events while waiting into \p chEvtWait().
 */
t_msg chMsgSendWithEvent(Thread *tp, t_msg msg, EventSource *esp) {

  chSysLock();

  fifo_insert(currp, &tp->p_msgqueue);
//  if (tp->p_state == PRWTMSG)
//    chSchReadyI(tp);
  chEvtSendI(esp);
  currp->p_msg = msg;
  chSchGoSleepS(PRSNDMSG);
  msg = currp->p_rdymsg;

  chSysUnlock();
  return msg;
}
#endif

#ifdef CH_USE_MESSAGES_TIMEOUT
static void unsend(void *p) {

// Test removed, it should never happen.
//  if (((Thread *)p)->p_state == PRSNDMSG)
  chSchReadyI(dequeue(p))->p_rdymsg = RDY_TIMEOUT;
}

/**
 * Sends a message to the specified thread with timeout specification. The
 * sender is stopped until the receiver executes a \p chMsgRelease().
 *
 * @param tp the pointer to the thread
 * @param msg the message. Note that it can be a pointer to a complex
 *            message structure.
 * @param time the number of ticks before the operation fails
 * @return the message return status from \p chMsgRelease() or
 *         \p RDY_TIMEOUT the specified time expired.
 * @note The server thread can also return data into the message structure
 *       if you need messages to be bidirectional, just define the structure
 *       according your needs. If you dont need complicated messages exchange
 *       you may just use the \p chMsgRelease() status code as response
 *       to the message.
 */
t_msg chMsgSendTimeout(Thread *tp, t_msg msg, t_time time) {
  VirtualTimer vt;

  chSysLock();

  chVTSetI(&vt, time, unsend, currp);
  fifo_insert(currp, &tp->p_msgqueue);
  if (tp->p_state == PRWTMSG)
    chSchReadyI(tp);
  currp->p_msg = msg;
  chSchGoSleepS(PRSNDMSG);
  msg = currp->p_rdymsg;
  if (chVTIsArmedI(&vt))
    chVTResetI(&vt);

  chSysUnlock();
  return msg;
}
#endif /* CH_USE_MESSAGES_TIMEOUT */

/**
 * Suspends the thread and waits for an incoming message.
 *
 * @return the pointer to the message structure. Note, it is always the
 *         message associated to the thread on the top of the messages queue.
 * @note You can assume that the data contained in the message is stable until
 *       you invoke \p chMsgRelease() because the sending thread is
 *       suspended until then.
 */
t_msg chMsgWait(void) {
  t_msg msg;

  chSysLock();

  if (!chMsgIsPendingI(currp))
    chSchGoSleepS(PRWTMSG);
  msg = chMsgGetI(currp);

  chSysUnlock();
  return msg;
}

/**
 * Returns the next message in the queue.
 *
 * @return the pointer to the message structure. Note, it is always the
 *         message associated to the thread on the top of the messages queue.
 *         If the queue is empty then \p NULL is returned.
 * @note You can assume that the data contained in the message is stable until
 *       you invoke \p chMsgRelease() because the sending thread is
 *       suspended until then. Always remember that the message data is not
 *       copied between the sender and the receiver, just a pointer is passed.
 */
t_msg chMsgGet(void) {
  t_msg msg;

  chSysLock();

  msg = chMsgIsPendingI(currp) ? chMsgGetI(currp) : NULL;

  chSysUnlock();
  return msg;
}

/**
 * Releases the thread waiting on top of the messages queue.
 *
 * @param msg the message returned to the message sender
 * @note You can call this function only if there is a message already in the
 *       queue else the result will be unpredictable (a crash most likely).
 *       Exiting from the \p chMsgWait() ensures you have at least one
 *       message in the queue so it is not a big deal.<br>
 *       The condition is not checked in order to make this code as fast as
 *       possible.
 */
void chMsgRelease(t_msg msg) {

  chSysLock();

//  if (!chMsgIsPendingI(currp)
  chSchWakeupS(fifo_remove(&currp->p_msgqueue), msg);

  chSysUnlock();
}

#endif /* CH_USE_MESSAGES */

/** @} */