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/* go-send-nb-small.c -- nonblocking send of something small on 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 <stdint.h>
#include "runtime.h"
#include "go-assert.h"
#include "go-panic.h"
#include "channel.h"
/* Prepare to send something on a nonblocking channel. Return true if
we acquired the channel, false if we did not acquire it because
there is no space to send a value. */
_Bool
__go_send_nonblocking_acquire (struct __go_channel *channel)
{
int i;
_Bool has_space;
i = pthread_mutex_lock (&channel->lock);
__go_assert (i == 0);
while (channel->selected_for_send)
runtime_cond_wait (&channel->cond, &channel->lock);
if (channel->is_closed)
{
i = pthread_mutex_unlock (&channel->lock);
__go_assert (i == 0);
__go_panic_msg ("send on closed channel");
}
if (channel->num_entries > 0)
has_space = ((channel->next_store + 1) % channel->num_entries
!= channel->next_fetch);
else
{
/* This is a synchronous channel. If somebody is current
sending, then we can't send. Otherwise, see if somebody is
waiting to receive, or see if we can synch with a select. */
if (channel->waiting_to_send)
{
/* Some other goroutine is currently sending on this
channel, which means that we can't. */
has_space = 0;
}
else if (channel->waiting_to_receive)
{
/* Some other goroutine is waiting to receive a value, so we
can send directly to them. */
has_space = 1;
}
else if (__go_synch_with_select (channel, 1))
{
/* We found a select waiting to receive data, so we can send
to that. */
__go_broadcast_to_select (channel);
has_space = 1;
}
else
{
/* Otherwise, we can't send, because nobody is waiting to
receive. */
has_space = 0;
}
if (has_space)
{
channel->waiting_to_send = 1;
__go_assert (channel->next_store == 0);
}
}
if (!has_space)
{
i = pthread_mutex_unlock (&channel->lock);
__go_assert (i == 0);
return 0;
}
return 1;
}
/* Send something 64 bits or smaller on a channel. */
_Bool
__go_send_nonblocking_small (struct __go_channel *channel, uint64_t val)
{
if (channel == NULL)
return 0;
__go_assert (channel->element_type->__size <= sizeof (uint64_t));
if (!__go_send_nonblocking_acquire (channel))
return 0;
channel->data[channel->next_store] = val;
__go_send_release (channel);
return 1;
}
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