107 lines
2.5 KiB
C
107 lines
2.5 KiB
C
/* go-send-nb-small.c -- nonblocking send of something small on a channel.
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Copyright 2009 The Go Authors. All rights reserved.
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file. */
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#include <stdint.h>
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#include "go-assert.h"
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#include "go-panic.h"
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#include "channel.h"
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/* Prepare to send something on a nonblocking channel. Return true if
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we acquired the channel, false if we did not acquire it because
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there is no space to send a value. */
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_Bool
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__go_send_nonblocking_acquire (struct __go_channel *channel)
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{
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int i;
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_Bool has_space;
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i = pthread_mutex_lock (&channel->lock);
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__go_assert (i == 0);
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while (channel->selected_for_send)
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{
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i = pthread_cond_wait (&channel->cond, &channel->lock);
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__go_assert (i == 0);
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}
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if (channel->is_closed)
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{
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i = pthread_mutex_unlock (&channel->lock);
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__go_assert (i == 0);
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__go_panic_msg ("send on closed channel");
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}
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if (channel->num_entries > 0)
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has_space = ((channel->next_store + 1) % channel->num_entries
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!= channel->next_fetch);
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else
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{
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/* This is a synchronous channel. If somebody is current
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sending, then we can't send. Otherwise, see if somebody is
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waiting to receive, or see if we can synch with a select. */
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if (channel->waiting_to_send)
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{
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/* Some other goroutine is currently sending on this
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channel, which means that we can't. */
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has_space = 0;
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}
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else if (channel->waiting_to_receive)
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{
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/* Some other goroutine is waiting to receive a value, so we
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can send directly to them. */
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has_space = 1;
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}
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else if (__go_synch_with_select (channel, 1))
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{
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/* We found a select waiting to receive data, so we can send
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to that. */
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__go_broadcast_to_select (channel);
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has_space = 1;
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}
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else
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{
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/* Otherwise, we can't send, because nobody is waiting to
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receive. */
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has_space = 0;
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}
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if (has_space)
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{
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channel->waiting_to_send = 1;
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__go_assert (channel->next_store == 0);
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}
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}
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if (!has_space)
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{
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i = pthread_mutex_unlock (&channel->lock);
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__go_assert (i == 0);
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return 0;
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}
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return 1;
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}
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/* Send something 64 bits or smaller on a channel. */
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_Bool
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__go_send_nonblocking_small (struct __go_channel *channel, uint64_t val)
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{
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__go_assert (channel->element_type->__size <= sizeof (uint64_t));
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if (!__go_send_nonblocking_acquire (channel))
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return 0;
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channel->data[channel->next_store] = val;
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__go_send_release (channel);
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return 1;
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}
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