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/*
*
* Copyright 2015 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
#import "GRPCCompletionQueue.h"
#import <grpc/grpc.h>
const grpc_completion_queue_attributes kCompletionQueueAttr = {
GRPC_CQ_CURRENT_VERSION, GRPC_CQ_NEXT, GRPC_CQ_DEFAULT_POLLING};
@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(
grpc_completion_queue_factory_lookup(&kCompletionQueueAttr), &kCompletionQueueAttr, 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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