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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 "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
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