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192 lines (158 loc) · 5.86 KB
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/*
* Copyright 2011-2016 David Karnok
*
* 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.
*/
package ix;
import java.util.*;
final class IxGroupBy<T, K, V> extends IxSource<T, GroupedIx<K, V>> {
static final Object NULL = new Object();
final IxFunction<? super T, ? extends K> keySelector;
final IxFunction<? super T, ? extends V> valueSelector;
IxGroupBy(Iterable<T> source, IxFunction<? super T, ? extends K> keySelector,
IxFunction<? super T, ? extends V> valueSelector) {
super(source);
this.keySelector = keySelector;
this.valueSelector = valueSelector;
}
@Override
public Iterator<GroupedIx<K, V>> iterator() {
return new GroupByIterator<T, K, V>(source.iterator(), keySelector, valueSelector);
}
static final class GroupByIterator<T, K, V> extends IxSourceIterator<T, GroupedIx<K, V>> {
final IxFunction<? super T, ? extends K> keySelector;
final IxFunction<? super T, ? extends V> valueSelector;
final Map<K, GroupedIterable<K, V>> groups;
final Queue<GroupedIterable<K, V>> queue;
GroupByIterator(Iterator<T> it, IxFunction<? super T, ? extends K> keySelector,
IxFunction<? super T, ? extends V> valueSelector) {
super(it);
this.keySelector = keySelector;
this.valueSelector = valueSelector;
this.groups = new HashMap<K, GroupedIterable<K, V>>();
this.queue = new ArrayDeque<GroupedIterable<K, V>>();
}
@Override
protected boolean moveNext() {
GroupedIterable<K, V> g = queue.poll();
if (g != null) {
value = g;
hasValue = true;
return true;
}
if (mainMoveNext()) {
g = queue.poll();
value = g;
hasValue = true;
return true;
}
done = true;
return false;
}
boolean mainMoveNext() {
for (;;) {
if (!it.hasNext()) {
groups.clear();
return false;
}
T v = it.next();
K key = keySelector.apply(v);
V val = valueSelector.apply(v);
GroupedIterable<K, V> g = groups.get(key);
if (g == null) {
g = new GroupedIterable<K, V>(key, this);
groups.put(key, g);
g.iterator.queue.offer(val != null ? val : NULL);
queue.offer(g);
return true;
} else {
g.iterator.queue.offer(val != null ? val : NULL);
}
}
}
boolean groupMoveNext(GroupByGroupIterator<K, V> groupIterator) {
if (done) {
return false;
}
for (;;) {
if (!it.hasNext()) {
groups.clear();
return false;
}
T v = it.next();
K key = keySelector.apply(v);
V val = valueSelector.apply(v);
GroupedIterable<K, V> g = groups.get(key);
if (g == null) {
g = new GroupedIterable<K, V>(key, this);
groups.put(key, g);
g.iterator.queue.offer(val != null ? val : NULL);
queue.offer(g);
} else {
g.iterator.queue.offer(val != null ? val : NULL);
if (EqualityHelper.INSTANCE.test(key, groupIterator.key)) {
return true;
}
}
}
}
}
static final class GroupedIterable<K, V> extends GroupedIx<K, V> {
final GroupByGroupIterator<K, V> iterator;
boolean once;
GroupedIterable(K key, GroupByIterator<?, K, V> parent) {
super(key);
this.iterator = new GroupByGroupIterator<K, V>(parent, key);
}
@Override
public Iterator<V> iterator() {
if (!once) {
once = true;
return iterator;
}
throw new IllegalStateException("This GroupedIx iterable can be consumed only once.");
}
@Override
public String toString() {
return "GroupedIterable[key=" + iterator.key + ", queue=" + iterator.queue.size() + "]";
}
}
static final class GroupByGroupIterator<K, V> extends IxBaseIterator<V> {
final GroupByIterator<?, K, V> parent;
final K key;
final ArrayDeque<Object> queue;
GroupByGroupIterator(GroupByIterator<?, K, V> parent, K key) {
this.parent = parent;
this.key = key;
this.queue = new ArrayDeque<Object>();
}
@SuppressWarnings("unchecked")
@Override
protected boolean moveNext() {
Object o = queue.poll();
if (o != null) {
value = o == NULL ? null : (V)o;
hasValue = true;
return true;
}
if (parent.groupMoveNext(this)) {
o = queue.poll();
value = o == NULL ? null : (V)o;
hasValue = true;
return true;
}
done = true;
return false;
}
}
}