1 files changed, 80 insertions, 0 deletions
diff --git a/Firestore/Source/Util/FSTDispatchQueue.mm b/Firestore/Source/Util/FSTDispatchQueue.mm
new file mode 100644
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+++ b/Firestore/Source/Util/FSTDispatchQueue.mm
@@ -0,0 +1,80 @@
+/*
+ * Copyright 2017 Google
+ *
+ * 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 <Foundation/Foundation.h>
+
+#import "Firestore/Source/Util/FSTAssert.h"
+#import "Firestore/Source/Util/FSTDispatchQueue.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface FSTDispatchQueue ()
+- (instancetype)initWithQueue:(dispatch_queue_t)queue NS_DESIGNATED_INITIALIZER;
+@end
+
+@implementation FSTDispatchQueue
+
++ (instancetype)queueWith:(dispatch_queue_t)dispatchQueue {
+  return [[FSTDispatchQueue alloc] initWithQueue:dispatchQueue];
+}
+
+- (instancetype)initWithQueue:(dispatch_queue_t)queue {
+  if (self = [super init]) {
+    _queue = queue;
+  }
+  return self;
+}
+
+- (void)verifyIsCurrentQueue {
+  FSTAssert([self onTargetQueue],
+            @"We are running on the wrong dispatch queue. Expected '%@' Actual: '%@'",
+            [self targetQueueLabel], [self currentQueueLabel]);
+}
+
+- (void)dispatchAsync:(void (^)(void))block {
+  FSTAssert(![self onTargetQueue],
+            @"dispatchAsync called when we are already running on target dispatch queue '%@'",
+            [self targetQueueLabel]);
+
+  dispatch_async(self.queue, block);
+}
+
+- (void)dispatchAsyncAllowingSameQueue:(void (^)(void))block {
+  dispatch_async(self.queue, block);
+}
+
+- (void)dispatchAfterDelay:(NSTimeInterval)delay block:(void (^)(void))block {
+  dispatch_time_t delayNs = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * NSEC_PER_SEC));
+  dispatch_after(delayNs, self.queue, block);
+}
+
+#pragma mark - Private Methods
+
+- (NSString *)currentQueueLabel {
+  return [NSString stringWithUTF8String:dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL)];
+}
+
+- (NSString *)targetQueueLabel {
+  return [NSString stringWithUTF8String:dispatch_queue_get_label(self.queue)];
+}
+
+- (BOOL)onTargetQueue {
+  return [[self currentQueueLabel] isEqualToString:[self targetQueueLabel]];
+}
+
+@end
+
+NS_ASSUME_NONNULL_END