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/*
*
* Copyright 2015-2016, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#import "GRPCCompletionQueue.h"
#import <grpc/grpc.h>
@implementation GRPCCompletionQueue
+ (instancetype)completionQueue {
static GRPCCompletionQueue *singleton = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
singleton = [[self alloc] init];
});
return singleton;
}
- (instancetype)init {
if ((self = [super init])) {
_unmanagedQueue = grpc_completion_queue_create(NULL);
// This is for the following block to capture the pointer by value (instead
// of retaining self and doing self->_unmanagedQueue). This is essential
// because the block doesn't end until after grpc_completion_queue_shutdown
// is called, and we only want that to happen after nobody's using the queue
// anymore (i.e. on self dealloc). So the block would never end if it
// retained self.
grpc_completion_queue *unmanagedQueue = _unmanagedQueue;
// Start a loop on a concurrent queue to read events from the completion
// queue and dispatch each.
static dispatch_once_t initialization;
static dispatch_queue_t gDefaultConcurrentQueue;
dispatch_once(&initialization, ^{
gDefaultConcurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
});
dispatch_async(gDefaultConcurrentQueue, ^{
while (YES) {
// The following call blocks until an event is available.
grpc_event event = grpc_completion_queue_next(unmanagedQueue,
gpr_inf_future(GPR_CLOCK_REALTIME),
NULL);
GRPCQueueCompletionHandler handler;
switch (event.type) {
case GRPC_OP_COMPLETE:
handler = (__bridge_transfer GRPCQueueCompletionHandler)event.tag;
handler(event.success);
break;
case GRPC_QUEUE_SHUTDOWN:
grpc_completion_queue_destroy(unmanagedQueue);
return;
default:
[NSException raise:@"Unrecognized completion type" format:@""];
}
};
});
}
return self;
}
- (void)dealloc {
// This makes the completion queue produce a GRPC_QUEUE_SHUTDOWN event *after*
// all other pending events are flushed. What this means is all the blocks
// passed to the gRPC C library as void* are eventually called, even if some
// are called after self is dealloc'd.
grpc_completion_queue_shutdown(_unmanagedQueue);
}
@end
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