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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010,
2011 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 chmboxes.c
* @brief Mailboxes code.
*
* @addtogroup mailboxes
* @details Asynchronous messages.
* <h2>Operation mode</h2>
* A mailbox is an asynchronous communication mechanism.<br>
* Operations defined for mailboxes:
* - <b>Post</b>: Posts a message on the mailbox in FIFO order.
* - <b>Post Ahead</b>: Posts a message on the mailbox with urgent
* priority.
* - <b>Fetch</b>: A message is fetched from the mailbox and removed
* from the queue.
* - <b>Reset</b>: The mailbox is emptied and all the stored messages
* are lost.
* .
* A message is a variable of type msg_t that is guaranteed to have
* the same size of and be compatible with (data) pointers (anyway an
* explicit cast is needed).
* If larger messages need to be exchanged then a pointer to a
* structure can be posted in the mailbox but the posting side has
* no predefined way to know when the message has been processed. A
* possible approach is to allocate memory (from a memory pool as
* example) from the posting side and free it on the fetching side.
* Another approach is to set a "done" flag into the structure pointed
* by the message.
* @pre In order to use the mailboxes APIs the @p CH_USE_MAILBOXES option
* must be enabled in @p chconf.h.
* @{
*/
#include "ch.h"
#if CH_USE_MAILBOXES || defined(__DOXYGEN__)
/**
* @brief Initializes a Mailbox object.
*
* @param[out] mbp the pointer to the Mailbox structure to be initialized
* @param[in] buf the circular messages buffer
* @param[in] n the buffer size as number of @p msg_t
*
* @init
*/
void chMBInit(Mailbox *mbp, msg_t *buf, cnt_t n) {
chDbgCheck((mbp != NULL) && (buf != NULL) && (n > 0), "chMBInit");
mbp->mb_buffer = mbp->mb_wrptr = mbp->mb_rdptr = buf;
mbp->mb_top = &buf[n];
chSemInit(&mbp->mb_emptysem, n);
chSemInit(&mbp->mb_fullsem, 0);
}
/**
* @brief Resets a Mailbox object.
* @details All the waiting threads are resumed with status @p RDY_RESET and
* the queued messages are lost.
*
* @param[in] mbp the pointer to an initialized Mailbox object
*
* @api
*/
void chMBReset(Mailbox *mbp) {
chDbgCheck(mbp != NULL, "chMBReset");
chSysLock();
mbp->mb_wrptr = mbp->mb_rdptr = mbp->mb_buffer;
chSemResetI(&mbp->mb_emptysem, mbp->mb_top - mbp->mb_buffer);
chSemResetI(&mbp->mb_fullsem, 0);
chSchRescheduleS();
chSysUnlock();
}
/**
* @brief Posts a message into a mailbox.
* @details The invoking thread waits until a empty slot in the mailbox becomes
* available or the specified time runs out.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[in] msg the message to be posted on the mailbox
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return The operation status.
* @retval RDY_OK if a message has been correctly posted.
* @retval RDY_RESET if the mailbox has been reset while waiting.
* @retval RDY_TIMEOUT if the operation has timed out.
*
* @api
*/
msg_t chMBPost(Mailbox *mbp, msg_t msg, systime_t time) {
msg_t rdymsg;
chSysLock();
rdymsg = chMBPostS(mbp, msg, time);
chSysUnlock();
return rdymsg;
}
/**
* @brief Posts a message into a mailbox.
* @details The invoking thread waits until a empty slot in the mailbox becomes
* available or the specified time runs out.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[in] msg the message to be posted on the mailbox
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return The operation status.
* @retval RDY_OK if a message has been correctly posted.
* @retval RDY_RESET if the mailbox has been reset while waiting.
* @retval RDY_TIMEOUT if the operation has timed out.
*
* @sclass
*/
msg_t chMBPostS(Mailbox *mbp, msg_t msg, systime_t time) {
msg_t rdymsg;
chDbgCheck(mbp != NULL, "chMBPostS");
rdymsg = chSemWaitTimeoutS(&mbp->mb_emptysem, time);
if (rdymsg == RDY_OK) {
*mbp->mb_wrptr++ = msg;
if (mbp->mb_wrptr >= mbp->mb_top)
mbp->mb_wrptr = mbp->mb_buffer;
chSemSignalI(&mbp->mb_fullsem);
chSchRescheduleS();
}
return rdymsg;
}
/**
* @brief Posts a message into a mailbox.
* @details This variant is non-blocking, the function returns a timeout
* condition if the queue is full.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[in] msg the message to be posted on the mailbox
* @return The operation status.
* @retval RDY_OK if a message has been correctly posted.
* @retval RDY_TIMEOUT if the mailbox is full and the message cannot be
* posted.
*
* @iclass
*/
msg_t chMBPostI(Mailbox *mbp, msg_t msg) {
chDbgCheck(mbp != NULL, "chMBPostI");
if (chSemGetCounterI(&mbp->mb_emptysem) <= 0)
return RDY_TIMEOUT;
chSemFastWaitI(&mbp->mb_emptysem);
*mbp->mb_wrptr++ = msg;
if (mbp->mb_wrptr >= mbp->mb_top)
mbp->mb_wrptr = mbp->mb_buffer;
chSemSignalI(&mbp->mb_fullsem);
return RDY_OK;
}
/**
* @brief Posts an high priority message into a mailbox.
* @details The invoking thread waits until a empty slot in the mailbox becomes
* available or the specified time runs out.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[in] msg the message to be posted on the mailbox
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return The operation status.
* @retval RDY_OK if a message has been correctly posted.
* @retval RDY_RESET if the mailbox has been reset while waiting.
* @retval RDY_TIMEOUT if the operation has timed out.
*
* @api
*/
msg_t chMBPostAhead(Mailbox *mbp, msg_t msg, systime_t time) {
msg_t rdymsg;
chSysLock();
rdymsg = chMBPostAheadS(mbp, msg, time);
chSysUnlock();
return rdymsg;
}
/**
* @brief Posts an high priority message into a mailbox.
* @details The invoking thread waits until a empty slot in the mailbox becomes
* available or the specified time runs out.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[in] msg the message to be posted on the mailbox
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return The operation status.
* @retval RDY_OK if a message has been correctly posted.
* @retval RDY_RESET if the mailbox has been reset while waiting.
* @retval RDY_TIMEOUT if the operation has timed out.
*
* @sclass
*/
msg_t chMBPostAheadS(Mailbox *mbp, msg_t msg, systime_t time) {
msg_t rdymsg;
chDbgCheck(mbp != NULL, "chMBPostAheadS");
rdymsg = chSemWaitTimeoutS(&mbp->mb_emptysem, time);
if (rdymsg == RDY_OK) {
if (--mbp->mb_rdptr < mbp->mb_buffer)
mbp->mb_rdptr = mbp->mb_top - 1;
*mbp->mb_rdptr = msg;
chSemSignalI(&mbp->mb_fullsem);
chSchRescheduleS();
}
return rdymsg;
}
/**
* @brief Posts an high priority message into a mailbox.
* @details This variant is non-blocking, the function returns a timeout
* condition if the queue is full.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[in] msg the message to be posted on the mailbox
* @return The operation status.
* @retval RDY_OK if a message has been correctly posted.
* @retval RDY_TIMEOUT if the mailbox is full and the message cannot be
* posted.
*
* @iclass
*/
msg_t chMBPostAheadI(Mailbox *mbp, msg_t msg) {
chDbgCheck(mbp != NULL, "chMBPostAheadI");
if (chSemGetCounterI(&mbp->mb_emptysem) <= 0)
return RDY_TIMEOUT;
chSemFastWaitI(&mbp->mb_emptysem);
if (--mbp->mb_rdptr < mbp->mb_buffer)
mbp->mb_rdptr = mbp->mb_top - 1;
*mbp->mb_rdptr = msg;
chSemSignalI(&mbp->mb_fullsem);
return RDY_OK;
}
/**
* @brief Retrieves a message from a mailbox.
* @details The invoking thread waits until a message is posted in the mailbox
* or the specified time runs out.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[out] msgp pointer to a message variable for the received message
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return The operation status.
* @retval RDY_OK if a message has been correctly fetched.
* @retval RDY_RESET if the mailbox has been reset while waiting.
* @retval RDY_TIMEOUT if the operation has timed out.
*
* @api
*/
msg_t chMBFetch(Mailbox *mbp, msg_t *msgp, systime_t time) {
msg_t rdymsg;
chSysLock();
rdymsg = chMBFetchS(mbp, msgp, time);
chSysUnlock();
return rdymsg;
}
/**
* @brief Retrieves a message from a mailbox.
* @details The invoking thread waits until a message is posted in the mailbox
* or the specified time runs out.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[out] msgp pointer to a message variable for the received message
* @param[in] time the number of ticks before the operation timeouts,
* the following special values are allowed:
* - @a TIME_IMMEDIATE immediate timeout.
* - @a TIME_INFINITE no timeout.
* .
* @return The operation status.
* @retval RDY_OK if a message has been correctly fetched.
* @retval RDY_RESET if the mailbox has been reset while waiting.
* @retval RDY_TIMEOUT if the operation has timed out.
*
* @sclass
*/
msg_t chMBFetchS(Mailbox *mbp, msg_t *msgp, systime_t time) {
msg_t rdymsg;
chDbgCheck((mbp != NULL) && (msgp != NULL), "chMBFetchS");
rdymsg = chSemWaitTimeoutS(&mbp->mb_fullsem, time);
if (rdymsg == RDY_OK) {
*msgp = *mbp->mb_rdptr++;
if (mbp->mb_rdptr >= mbp->mb_top)
mbp->mb_rdptr = mbp->mb_buffer;
chSemSignalI(&mbp->mb_emptysem);
chSchRescheduleS();
}
return rdymsg;
}
/**
* @brief Retrieves a message from a mailbox.
* @details This variant is non-blocking, the function returns a timeout
* condition if the queue is full.
*
* @param[in] mbp the pointer to an initialized Mailbox object
* @param[out] msgp pointer to a message variable for the received message
* @return The operation status.
* @retval RDY_OK if a message has been correctly fetched.
* @retval RDY_TIMEOUT if the mailbox is empty and a message cannot be
* fetched.
*
* @iclass
*/
msg_t chMBFetchI(Mailbox *mbp, msg_t *msgp) {
chDbgCheck((mbp != NULL) && (msgp != NULL), "chMBFetchI");
if (chSemGetCounterI(&mbp->mb_fullsem) <= 0)
return RDY_TIMEOUT;
*msgp = *mbp->mb_rdptr++;
if (mbp->mb_rdptr >= mbp->mb_top)
mbp->mb_rdptr = mbp->mb_buffer;
chSemSignalI(&mbp->mb_emptysem);
return RDY_OK;
}
#endif /* CH_USE_MAILBOXES */
/** @} */
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