Initial checkin of gRPC to third_party/

third_party/grpc/src/objective-c/RxLibrary/private/GRXNSFastEnumerator.m

+/*
+ *
+ * Copyright 2015, 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 "GRXNSFastEnumerator.h"
+
+@implementation GRXNSFastEnumerator {
+  id<NSFastEnumeration> _container;
+  NSFastEnumerationState _state;
+  // Number of elements of the container currently in the _state.itemsPtr array.
+  NSUInteger _count;
+  // The index of the next object to return from the _state.itemsPtr array.
+  NSUInteger _index;
+  // A "buffer of one element," for the containers that enumerate their elements one by one. Those
+  // will set _state.itemsPtr to point to this.
+  // The NSFastEnumeration protocol requires it to be __unsafe_unretained, but that's alright
+  // because the only use we'd make of its value is to return it immediately as the result of
+  // nextObject.
+  __unsafe_unretained id _bufferValue;
+  // Neither NSEnumerator nor NSFastEnumeration instances are required to work correctly when the
+  // underlying container is mutated during iteration. The expectation is that an exception is
+  // thrown when that happens. So we check for mutations.
+  unsigned long _mutationFlag;
+  BOOL _mutationFlagIsSet;
+}
+
+- (instancetype)init {
+  return [self initWithContainer:nil];
+}
+
+// Designated initializer.
+- (instancetype)initWithContainer:(id<NSFastEnumeration>)container {
+  if ((self = [super init])) {
+    _container = container;
+  }
+  return self;
+}
+
+- (id)nextObject {
+  if (_index == _count) {
+    _index = 0;
+    _count = [_container countByEnumeratingWithState:&_state objects:&_bufferValue count:1];
+    if (_count == 0) {
+      // Enumeration is over.
+      _container = nil;
+      return nil;
+    }
+    if (_mutationFlagIsSet) {
+      NSAssert(_mutationFlag == *(_state.mutationsPtr),
+               @"container was mutated while being enumerated");
+    } else {
+      _mutationFlag = *(_state.mutationsPtr);
+      _mutationFlagIsSet = YES;
+    }
+  }
+  return _state.itemsPtr[_index++];
+}
+@end