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/* go-rec-nb-small.c -- nonblocking receive of something smal 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 "go-assert.h"
#include "go-panic.h"
#include "channel.h"
/* Prepare to receive something on a nonblocking channel. */
int
__go_receive_nonblocking_acquire (struct __go_channel *channel)
{
int i;
_Bool has_data;
i = pthread_mutex_lock (&channel->lock);
__go_assert (i == 0);
while (channel->selected_for_receive)
{
i = pthread_cond_wait (&channel->cond, &channel->lock);
__go_assert (i == 0);
}
if (channel->is_closed
&& (channel->num_entries == 0
? channel->next_store == 0
: channel->next_fetch == channel->next_store))
{
if (channel->saw_close)
{
++channel->closed_op_count;
if (channel->closed_op_count >= MAX_CLOSED_OPERATIONS)
{
i = pthread_mutex_unlock (&channel->lock);
__go_assert (i == 0);
__go_panic_msg ("too many operations on closed channel");
}
}
channel->saw_close = 1;
__go_unlock_and_notify_selects (channel);
return RECEIVE_NONBLOCKING_ACQUIRE_CLOSED;
}
if (channel->num_entries > 0)
has_data = channel->next_fetch != channel->next_store;
else
{
if (channel->waiting_to_receive)
{
/* Some other goroutine is already waiting for data on this
channel, so we can't pick it up. */
has_data = 0;
}
else if (channel->next_store > 0)
{
/* There is data on the channel. */
has_data = 1;
}
else if (__go_synch_with_select (channel, 0))
{
/* We synched up with a select sending data, so there will
be data for us shortly. Tell the select to go, and then
wait for the data. */
__go_broadcast_to_select (channel);
while (channel->next_store == 0)
{
i = pthread_cond_wait (&channel->cond, &channel->lock);
__go_assert (i == 0);
}
has_data = 1;
}
else
{
/* Otherwise there is no data. */
has_data = 0;
}
if (has_data)
{
channel->waiting_to_receive = 1;
__go_assert (channel->next_store == 1);
}
}
if (!has_data)
{
i = pthread_mutex_unlock (&channel->lock);
__go_assert (i == 0);
return RECEIVE_NONBLOCKING_ACQUIRE_NODATA;
}
return RECEIVE_NONBLOCKING_ACQUIRE_DATA;
}
/* Receive something 64 bits or smaller on a nonblocking channel. */
struct __go_receive_nonblocking_small
__go_receive_nonblocking_small (struct __go_channel *channel)
{
struct __go_receive_nonblocking_small ret;
__go_assert (channel->element_size <= sizeof (uint64_t));
int data = __go_receive_nonblocking_acquire (channel);
if (data != RECEIVE_NONBLOCKING_ACQUIRE_DATA)
{
ret.__val = 0;
ret.__success = data == RECEIVE_NONBLOCKING_ACQUIRE_CLOSED;
return ret;
}
ret.__val = channel->data[channel->next_fetch];
__go_receive_release (channel);
ret.__success = 1;
return ret;
}
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