183 lines
5.9 KiB
Java
183 lines
5.9 KiB
Java
/*
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* Copyright 2012 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.channel;
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import io.netty.buffer.ByteBuf;
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import io.netty.buffer.ByteBufAllocator;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* The {@link RecvByteBufAllocator} that automatically increases and
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* decreases the predicted buffer size on feed back.
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* <p>
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* It gradually increases the expected number of readable bytes if the previous
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* read fully filled the allocated buffer. It gradually decreases the expected
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* number of readable bytes if the read operation was not able to fill a certain
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* amount of the allocated buffer two times consecutively. Otherwise, it keeps
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* returning the same prediction.
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*/
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public class AdaptiveRecvByteBufAllocator implements RecvByteBufAllocator {
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static final int DEFAULT_MINIMUM = 64;
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static final int DEFAULT_INITIAL = 1024;
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static final int DEFAULT_MAXIMUM = 65536;
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private static final int INDEX_INCREMENT = 4;
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private static final int INDEX_DECREMENT = 1;
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private static final int[] SIZE_TABLE;
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static {
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List<Integer> sizeTable = new ArrayList<Integer>();
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for (int i = 16; i < 512; i += 16) {
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sizeTable.add(i);
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}
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for (int i = 512; i > 0; i <<= 1) {
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sizeTable.add(i);
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}
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SIZE_TABLE = new int[sizeTable.size()];
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for (int i = 0; i < SIZE_TABLE.length; i ++) {
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SIZE_TABLE[i] = sizeTable.get(i);
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}
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}
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public static final AdaptiveRecvByteBufAllocator DEFAULT = new AdaptiveRecvByteBufAllocator();
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private static int getSizeTableIndex(final int size) {
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for (int low = 0, high = SIZE_TABLE.length - 1;;) {
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if (high < low) {
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return low;
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}
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if (high == low) {
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return high;
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}
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int mid = low + high >>> 1;
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int a = SIZE_TABLE[mid];
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int b = SIZE_TABLE[mid + 1];
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if (size > b) {
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low = mid + 1;
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} else if (size < a) {
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high = mid - 1;
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} else if (size == a) {
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return mid;
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} else {
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return mid + 1;
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}
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}
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}
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private static final class HandleImpl implements Handle {
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private final int minIndex;
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private final int maxIndex;
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private int index;
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private int nextReceiveBufferSize;
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private boolean decreaseNow;
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HandleImpl(int minIndex, int maxIndex, int initial) {
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this.minIndex = minIndex;
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this.maxIndex = maxIndex;
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index = getSizeTableIndex(initial);
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nextReceiveBufferSize = SIZE_TABLE[index];
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}
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@Override
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public ByteBuf allocate(ByteBufAllocator alloc) {
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return alloc.ioBuffer(nextReceiveBufferSize);
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}
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@Override
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public int guess() {
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return nextReceiveBufferSize;
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}
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@Override
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public void record(int actualReadBytes) {
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if (actualReadBytes <= SIZE_TABLE[Math.max(0, index - INDEX_DECREMENT - 1)]) {
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if (decreaseNow) {
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index = Math.max(index - INDEX_DECREMENT, minIndex);
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nextReceiveBufferSize = SIZE_TABLE[index];
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decreaseNow = false;
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} else {
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decreaseNow = true;
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}
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} else if (actualReadBytes >= nextReceiveBufferSize) {
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index = Math.min(index + INDEX_INCREMENT, maxIndex);
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nextReceiveBufferSize = SIZE_TABLE[index];
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decreaseNow = false;
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}
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}
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}
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private final int minIndex;
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private final int maxIndex;
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private final int initial;
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/**
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* Creates a new predictor with the default parameters. With the default
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* parameters, the expected buffer size starts from {@code 1024}, does not
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* go down below {@code 64}, and does not go up above {@code 65536}.
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*/
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private AdaptiveRecvByteBufAllocator() {
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this(DEFAULT_MINIMUM, DEFAULT_INITIAL, DEFAULT_MAXIMUM);
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}
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/**
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* Creates a new predictor with the specified parameters.
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*
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* @param minimum the inclusive lower bound of the expected buffer size
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* @param initial the initial buffer size when no feed back was received
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* @param maximum the inclusive upper bound of the expected buffer size
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*/
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public AdaptiveRecvByteBufAllocator(int minimum, int initial, int maximum) {
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if (minimum <= 0) {
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throw new IllegalArgumentException("minimum: " + minimum);
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}
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if (initial < minimum) {
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throw new IllegalArgumentException("initial: " + initial);
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}
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if (maximum < initial) {
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throw new IllegalArgumentException("maximum: " + maximum);
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}
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int minIndex = getSizeTableIndex(minimum);
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if (SIZE_TABLE[minIndex] < minimum) {
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this.minIndex = minIndex + 1;
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} else {
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this.minIndex = minIndex;
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}
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int maxIndex = getSizeTableIndex(maximum);
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if (SIZE_TABLE[maxIndex] > maximum) {
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this.maxIndex = maxIndex - 1;
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} else {
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this.maxIndex = maxIndex;
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}
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this.initial = initial;
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}
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@Override
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public Handle newHandle() {
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return new HandleImpl(minIndex, maxIndex, initial);
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}
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}
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