gcc/libgo/runtime/go-chan-len.c

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/* go-chan-len.c -- the len 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 len function applied to a channel--the number of
elements in 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. */
int
__go_chan_len (struct __go_channel *channel)
{
int i;
int ret;
if (channel == NULL)
return 0;
i = pthread_mutex_lock (&channel->lock);
__go_assert (i == 0);
if (channel->num_entries == 0)
ret = 0;
else if (channel->next_fetch == channel->next_store)
ret = 0;
else
ret = ((channel->next_store + channel->num_entries - channel->next_fetch)
% channel->num_entries);
i = pthread_mutex_unlock (&channel->lock);
__go_assert (i == 0);
return ret;
}