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/*
*
* 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
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