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/*
* 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 "FTreeSortedDictionaryEnumerator.h"
@interface FTreeSortedDictionaryEnumerator()
@property (nonatomic, strong) FTreeSortedDictionary* immutableSortedDictionary;
@property (nonatomic, strong) NSMutableArray* stack;
@property (nonatomic) BOOL isReverse;
@end
@implementation FTreeSortedDictionaryEnumerator
- (id)initWithImmutableSortedDictionary:(FTreeSortedDictionary *)aDict
startKey:(id)startKey isReverse:(BOOL)reverse {
self = [super init];
if (self) {
self.immutableSortedDictionary = aDict;
self.stack = [[NSMutableArray alloc] init];
self.isReverse = reverse;
NSComparator comparator = aDict.comparator;
id<FLLRBNode> node = self.immutableSortedDictionary.root;
NSInteger cmp;
while(![node isEmpty]) {
cmp = startKey ? comparator(node.key, startKey) : 1;
// flip the comparison if we're going in reverse
if (self.isReverse) cmp *= -1;
if (cmp < 0) {
// This node is less than our start key. Ignore it.
if (self.isReverse) {
node = node.left;
} else {
node = node.right;
}
} else if (cmp == 0) {
// This node is exactly equal to our start key. Push it on the stack, but stop iterating:
[self.stack addObject:node];
break;
} else {
// This node is greater than our start key, add it to the stack and move on to the next one.
[self.stack addObject:node];
if (self.isReverse) {
node = node.right;
} else {
node = node.left;
}
}
}
}
return self;
}
- (id)nextObject {
if([self.stack count] == 0) {
return nil;
}
id<FLLRBNode> node = nil;
@synchronized(self.stack) {
node = [self.stack lastObject];
[self.stack removeLastObject];
}
id result = node.key;
if (self.isReverse) {
node = node.left;
while (![node isEmpty]) {
[self.stack addObject:node];
node = node.right;
}
} else {
node = node.right;
while (![node isEmpty]) {
[self.stack addObject:node];
node = node.left;
}
}
return result;
}
@end
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