/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx.internal.operators;
import java.util.concurrent.atomic.
AtomicBoolean;
import rx.*;
import rx.
Observable.
Operator;
/**
* Returns the element at a specified index in a sequence.
* @param <T> the value type
*/
public final class
OperatorElementAt<T> implements
Operator<T, T> {
final int
index;
final boolean
hasDefault;
final T
defaultValue;
public
OperatorElementAt(int
index) {
this(
index, null, false);
}
public
OperatorElementAt(int
index, T
defaultValue) {
this(
index,
defaultValue, true);
}
private
OperatorElementAt(int
index, T
defaultValue, boolean
hasDefault) {
if (
index < 0) {
throw new
IndexOutOfBoundsException(
index + " is out of bounds");
}
this.
index =
index;
this.
defaultValue =
defaultValue;
this.
hasDefault =
hasDefault;
}
@
Override
public
Subscriber<? super T>
call(final
Subscriber<? super T>
child) {
Subscriber<T>
parent = new
Subscriber<T>() {
private int
currentIndex;
@
Override
public void
onNext(T
value) {
if (
currentIndex++ ==
index) {
child.
onNext(
value);
child.
onCompleted();
unsubscribe();
}
}
@
Override
public void
onError(
Throwable e) {
child.
onError(
e);
}
@
Override
public void
onCompleted() {
if (
currentIndex <=
index) {
// If "subscriber.onNext(value)" is called, currentIndex must be greater than index
if (
hasDefault) {
child.
onNext(
defaultValue);
child.
onCompleted();
} else {
child.
onError(new
IndexOutOfBoundsException(
index + " is out of bounds"));
}
}
}
@
Override
public void
setProducer(
Producer p) {
child.
setProducer(new
InnerProducer(
p));
}
};
child.
add(
parent);
return
parent;
}
/**
* A producer that wraps another Producer and requests Long.MAX_VALUE
* when the first positive request() call comes in.
*/
static class
InnerProducer extends
AtomicBoolean implements
Producer {
/** */
private static final long
serialVersionUID = 1L;
final
Producer actual;
public
InnerProducer(
Producer actual) {
this.
actual =
actual;
}
@
Override
public void
request(long
n) {
if (
n < 0) {
throw new
IllegalArgumentException("n >= 0 required");
}
if (
n > 0 &&
compareAndSet(false, true)) {
// trigger the fast-path since the operator is going
// to skip all but the indexth element
actual.
request(
Long.
MAX_VALUE);
}
}
}
}