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/*
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/>.
*/
/**
* @file chmsg.c
* @brief Messages code.
*
* @addtogroup messages
* @{
*/
#include "ch.h"
#if CH_USE_MESSAGES
#if CH_USE_MESSAGES_PRIORITY
#define msg_insert(tp, qp) prio_insert(tp, qp)
#else
#define msg_insert(tp, qp) queue_insert(tp, qp)
#endif
/**
* @brief Sends a message to the specified thread.
* @details The sender is stopped until the receiver executes a
* @p chMsgRelease()after receiving the message.
*
* @param[in] tp the pointer to the thread
* @param[in] msg the message
* @return The answer message from @p chMsgRelease().
*/
msg_t chMsgSend(Thread *tp, msg_t msg) {
Thread *ctp = currp;
chDbgCheck(tp != NULL, "chMsgSend");
chSysLock();
ctp->p_msg = msg;
ctp->p_u.wtobjp = &tp->p_msgqueue;
msg_insert(ctp, &tp->p_msgqueue);
if (tp->p_state == THD_STATE_WTMSG)
chSchReadyI(tp);
chSchGoSleepS(THD_STATE_SNDMSG);
msg = ctp->p_u.rdymsg;
chSysUnlock();
return msg;
}
/**
* @brief Suspends the thread and waits for an incoming message.
* @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.
*
* @return The pointer to the message structure. Note, it is
* always the message associated to the thread on the
* top of the messages queue.
*/
msg_t chMsgWait(void) {
msg_t msg;
chSysLock();
if (!chMsgIsPendingI(currp))
chSchGoSleepS(THD_STATE_WTMSG);
msg = chMsgGetI(currp);
chSysUnlock();
return msg;
}
/**
* @brief Returns the next message in the queue.
* @note You can assume that the data pointed by 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.
*
* @return The pointer to the message structure. Note, it is
* always the message associated to the thread on the
* top of the messages queue.
* @retval NULL if the queue is empty.
*/
msg_t chMsgGet(void) {
msg_t msg;
chSysLock();
msg = chMsgIsPendingI(currp) ? chMsgGetI(currp) : (msg_t)NULL;
chSysUnlock();
return msg;
}
/**
* @brief Releases the thread waiting on top of the messages queue.
* @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 only tested in debug mode in order to make this
* code as fast as possible.
*
* @param[in] msg the message returned to the message sender
*/
void chMsgRelease(msg_t msg) {
chSysLock();
chDbgAssert(chMsgIsPendingI(currp),
"chMsgRelease(), #1",
"no message pending");
chSchWakeupS(fifo_remove(&currp->p_msgqueue), msg);
chSysUnlock();
}
#endif /* CH_USE_MESSAGES */
/** @} */
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