docs/hazmat/bindings/index.rst


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.. hazmat::

Bindings
========

.. currentmodule:: cryptography.hazmat.bindings

``cryptography`` aims to provide low-level CFFI based bindings to multiple
native C libraries. These provide no automatic initialization of the library
and may not provide complete wrappers for its API.

Using these functions directly is likely to require you to be careful in
managing memory allocation, locking and other resources.


Individual bindings
-------------------

.. toctree::
    :maxdepth: 1

    openssl
    commoncrypto
/*
    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;

  chDbgCheckClassS();
  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) {

  chDbgCheckClassI();
  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;

  chDbgCheckClassS();
  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) {

  chDbgCheckClassI();
  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;

  chDbgCheckClassS();
  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) {

  chDbgCheckClassI();
  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 */

/** @} */