119 lines
2.7 KiB
C
119 lines
2.7 KiB
C
/* go-rec-nb-small.c -- nonblocking receive of something smal 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 receive something on a nonblocking channel. */
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int
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__go_receive_nonblocking_acquire (struct __go_channel *channel)
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{
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int i;
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_Bool has_data;
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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_receive)
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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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&& (channel->num_entries == 0
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? channel->next_store == 0
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: channel->next_fetch == channel->next_store))
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{
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__go_unlock_and_notify_selects (channel);
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return RECEIVE_NONBLOCKING_ACQUIRE_CLOSED;
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}
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if (channel->num_entries > 0)
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has_data = channel->next_fetch != channel->next_store;
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else
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{
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if (channel->waiting_to_receive)
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{
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/* Some other goroutine is already waiting for data on this
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channel, so we can't pick it up. */
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has_data = 0;
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}
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else if (channel->next_store > 0)
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{
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/* There is data on the channel. */
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has_data = 1;
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}
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else if (__go_synch_with_select (channel, 0))
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{
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/* We synched up with a select sending data, so there will
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be data for us shortly. Tell the select to go, and then
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wait for the data. */
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__go_broadcast_to_select (channel);
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while (channel->next_store == 0)
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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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has_data = 1;
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}
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else
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{
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/* Otherwise there is no data. */
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has_data = 0;
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}
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if (has_data)
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{
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channel->waiting_to_receive = 1;
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__go_assert (channel->next_store == 1);
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}
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}
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if (!has_data)
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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 RECEIVE_NONBLOCKING_ACQUIRE_NODATA;
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}
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return RECEIVE_NONBLOCKING_ACQUIRE_DATA;
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}
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/* Receive something 64 bits or smaller on a nonblocking channel. */
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struct __go_receive_nonblocking_small
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__go_receive_nonblocking_small (struct __go_channel *channel)
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{
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struct __go_receive_nonblocking_small ret;
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__go_assert (channel->element_size <= sizeof (uint64_t));
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int data = __go_receive_nonblocking_acquire (channel);
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if (data != RECEIVE_NONBLOCKING_ACQUIRE_DATA)
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{
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ret.__val = 0;
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ret.__success = 0;
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ret.__closed = data == RECEIVE_NONBLOCKING_ACQUIRE_CLOSED;
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return ret;
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}
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ret.__val = channel->data[channel->next_fetch];
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__go_receive_release (channel);
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ret.__success = 1;
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ret.__closed = 0;
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return ret;
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}
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