Initial checkin of gRPC to third_party/

third_party/grpc/src/objective-c/GRPCClient/private/GRPCCompletionQueue.m

+/*
+ *
+ * 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 {
+  return [[self alloc] init];
+}
+
+- (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