libgo/runtime/go-chan-cap.c

   1 /* go-chan-cap.c -- the cap function applied to a channel.
   2
   3    Copyright 2009 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include <stddef.h>
   8
   9 #include "go-assert.h"
  10 #include "channel.h"
  11
  12 /* Return the cap function applied to a channel--the size of the
  13    buffer.  This could be done inline but I'm doing it as a function
  14    for now to make it easy to change the channel structure.  */
  15
  16 size_t
  17 __go_chan_cap (struct __go_channel *channel)
  18 {
  19   int i;
  20   size_t ret;
  21
  22   if (channel == NULL)
  23     return 0;
  24
  25   i = pthread_mutex_lock (&channel->lock);
  26   __go_assert (i == 0);
  27
  28   if (channel->num_entries == 0)
  29     ret = 0;
  30   else
  31     {
  32       /* One slot is always unused.  We added 1 when we created the
  33          channel.  */
  34       ret = channel->num_entries - 1;
  35     }
  36
  37   i = pthread_mutex_unlock (&channel->lock);
  38   __go_assert  (i == 0);
  39
  40   return ret;
  41 }