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/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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 org.mozilla.thirdparty.com.google.android.exoplayer2.util;
import androidx.annotation.Nullable;
import java.util.Arrays;
import org.checkerframework.checker.nullness.compatqual.NullableType;
/** A utility class to keep a queue of values with timestamps. This class is thread safe. */
public final class TimedValueQueue<V> {
private static final int INITIAL_BUFFER_SIZE = 10;
// Looping buffer for timestamps and values
private long[] timestamps;
private @NullableType V[] values;
private int first;
private int size;
public TimedValueQueue() {
this(INITIAL_BUFFER_SIZE);
}
/** Creates a TimedValueBuffer with the given initial buffer size. */
public TimedValueQueue(int initialBufferSize) {
timestamps = new long[initialBufferSize];
values = newArray(initialBufferSize);
}
/**
* Associates the specified value with the specified timestamp. All new values should have a
* greater timestamp than the previously added values. Otherwise all values are removed before
* adding the new one.
*/
public synchronized void add(long timestamp, V value) {
clearBufferOnTimeDiscontinuity(timestamp);
doubleCapacityIfFull();
addUnchecked(timestamp, value);
}
/** Removes all of the values. */
public synchronized void clear() {
first = 0;
size = 0;
Arrays.fill(values, null);
}
/** Returns number of the values buffered. */
public synchronized int size() {
return size;
}
/**
* Returns the value with the greatest timestamp which is less than or equal to the given
* timestamp. Removes all older values and the returned one from the buffer.
*
* @param timestamp The timestamp value.
* @return The value with the greatest timestamp which is less than or equal to the given
* timestamp or null if there is no such value.
* @see #poll(long)
*/
public synchronized @Nullable V pollFloor(long timestamp) {
return poll(timestamp, /* onlyOlder= */ true);
}
/**
* Returns the value with the closest timestamp to the given timestamp. Removes all older values
* including the returned one from the buffer.
*
* @param timestamp The timestamp value.
* @return The value with the closest timestamp or null if the buffer is empty.
* @see #pollFloor(long)
*/
public synchronized @Nullable V poll(long timestamp) {
return poll(timestamp, /* onlyOlder= */ false);
}
/**
* Returns the value with the closest timestamp to the given timestamp. Removes all older values
* including the returned one from the buffer.
*
* @param timestamp The timestamp value.
* @param onlyOlder Whether this method can return a new value in case its timestamp value is
* closest to {@code timestamp}.
* @return The value with the closest timestamp or null if the buffer is empty or there is no
* older value and {@code onlyOlder} is true.
*/
@Nullable
private V poll(long timestamp, boolean onlyOlder) {
V value = null;
long previousTimeDiff = Long.MAX_VALUE;
while (size > 0) {
long timeDiff = timestamp - timestamps[first];
if (timeDiff < 0 && (onlyOlder || -timeDiff >= previousTimeDiff)) {
break;
}
previousTimeDiff = timeDiff;
value = values[first];
values[first] = null;
first = (first + 1) % values.length;
size--;
}
return value;
}
private void clearBufferOnTimeDiscontinuity(long timestamp) {
if (size > 0) {
int last = (first + size - 1) % values.length;
if (timestamp <= timestamps[last]) {
clear();
}
}
}
private void doubleCapacityIfFull() {
int capacity = values.length;
if (size < capacity) {
return;
}
int newCapacity = capacity * 2;
long[] newTimestamps = new long[newCapacity];
V[] newValues = newArray(newCapacity);
// Reset the loop starting index to 0 while coping to the new buffer.
// First copy the values from 'first' index to the end of original array.
int length = capacity - first;
System.arraycopy(timestamps, first, newTimestamps, 0, length);
System.arraycopy(values, first, newValues, 0, length);
// Then the values from index 0 to 'first' index.
if (first > 0) {
System.arraycopy(timestamps, 0, newTimestamps, length, first);
System.arraycopy(values, 0, newValues, length, first);
}
timestamps = newTimestamps;
values = newValues;
first = 0;
}
private void addUnchecked(long timestamp, V value) {
int next = (first + size) % values.length;
timestamps[next] = timestamp;
values[next] = value;
size++;
}
@SuppressWarnings("unchecked")
private static <V> V[] newArray(int length) {
return (V[]) new Object[length];
}
}
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