libgo/runtime/go-chan-cap.c


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/* go-chan-cap.c -- the cap function applied to a channel.

   Copyright 2009 The Go Authors. All rights reserved.
   Use of this source code is governed by a BSD-style
   license that can be found in the LICENSE file.  */

#include <stddef.h>

#include "go-assert.h"
#include "channel.h"

/* Return the cap function applied to a channel--the size of the
   buffer.  This could be done inline but I'm doing it as a function
   for now to make it easy to change the channel structure.  */

size_t
__go_chan_cap (struct __go_channel *channel)
{
  int i;
  size_t ret;

  if (channel == NULL)
    return 0;

  i = pthread_mutex_lock (&channel->lock);
  __go_assert (i == 0);

  if (channel->num_entries == 0)
    ret = 0;
  else
    {
      /* One slot is always unused.  We added 1 when we created the
	 channel.  */
      ret = channel->num_entries - 1;
    }

  i = pthread_mutex_unlock (&channel->lock);
  __go_assert  (i == 0);

  return ret;
}