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RIOT/sys/pipe/pipe.c 2.95 KB
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  /*
   * Copyright (C) 2014  René Kijewski  <rene.kijewski@fu-berlin.de>
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library 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
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
   */
  
  /**
   * @ingroup     sys_pipe
   * @{
   * @file
   * @brief       Implementation for statically allocated pipes.
   * @author      René Kijewski <rene.kijewski@fu-berlin.de>
   * @}
   */
  
  #include "irq.h"
  #include "pipe.h"
  #include "sched.h"
  
  typedef unsigned (*ringbuffer_op_t)(ringbuffer_t *restrict rb, char *buf, unsigned n);
  
  static ssize_t pipe_rw(ringbuffer_t *rb,
                         void *buf,
                         size_t n,
                         thread_t **other_op_blocked,
                         thread_t **this_op_blocked,
                         ringbuffer_op_t ringbuffer_op)
  {
      if (n == 0) {
          return 0;
      }
  
      while (1) {
          unsigned old_state = irq_disable();
  
          unsigned count = ringbuffer_op(rb, buf, n);
  
          if (count > 0) {
              thread_t *other_thread = *other_op_blocked;
              int other_prio = -1;
              if (other_thread) {
                  *other_op_blocked = NULL;
                  other_prio = other_thread->priority;
                  sched_set_status(other_thread, STATUS_PENDING);
              }
  
              irq_restore(old_state);
  
              if (other_prio >= 0) {
                  sched_switch(other_prio);
              }
  
              return count;
          }
          else if (*this_op_blocked || irq_is_in()) {
              irq_restore(old_state);
              return 0;
          }
          else {
              *this_op_blocked = (thread_t *) sched_active_thread;
  
              sched_set_status((thread_t *) sched_active_thread, STATUS_SLEEPING);
              irq_restore(old_state);
              thread_yield_higher();
          }
      }
  }
  
  ssize_t pipe_read(pipe_t *pipe, void *buf, size_t n)
  {
      return pipe_rw(pipe->rb, (char *) buf, n,
                     &pipe->write_blocked, &pipe->read_blocked, ringbuffer_get);
  }
  
  ssize_t pipe_write(pipe_t *pipe, const void *buf, size_t n)
  {
      return pipe_rw(pipe->rb, (char *) buf, n,
                     &pipe->read_blocked, &pipe->write_blocked, (ringbuffer_op_t) ringbuffer_add);
  }
  
  void pipe_init(pipe_t *pipe, ringbuffer_t *rb, void (*free)(void *))
  {
      *pipe = (pipe_t) {
          .rb = rb,
          .read_blocked = NULL,
          .write_blocked = NULL,
          .free = free,
      };
  }