c13419750d
Motivation: Before this changes Bzip2BitReader and Bzip2BitWriter accessed to ByteBuf byte by byte. So tests for Bzip2 compression codec takes a lot of time if we ran them with paranoid level of resource leak detection. For more information see comments to #2681 and #2689. Modifications: - Increased size of bit buffers from 8 to 64 bits. - Improved reading and writing operations. - Save link to incoming ByteBuf inside Bzip2BitReader. - Added methods to check possible readable bits and bytes in Bzip2BitReader. - Updated Bzip2 classes to use new API of Bzip2BitReader. - Added new constants to Bzip2Constants. Result: Increased size of bit buffers and improved performance of Bzip2 compression codec (for general work by 13% and for tests with paranoid level of resource leak detection by 55%).
158 lines
4.9 KiB
Java
158 lines
4.9 KiB
Java
/*
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* Copyright 2014 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.handler.codec.compression;
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import io.netty.buffer.ByteBuf;
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/**
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* An bit reader that allows the reading of single bit booleans, bit strings of
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* arbitrary length (up to 32 bits), and bit aligned 32-bit integers. A single byte
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* at a time is read from the {@link ByteBuf} when more bits are required.
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*/
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class Bzip2BitReader {
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/**
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* Maximum count of possible readable bytes to check.
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*/
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private static final int MAX_COUNT_OF_READABLE_BYTES = Integer.MAX_VALUE >>> 3;
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/**
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* The {@link ByteBuf} from which to read data.
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*/
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private ByteBuf in;
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/**
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* A buffer of bits read from the input stream that have not yet been returned.
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*/
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private long bitBuffer;
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/**
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* The number of bits currently buffered in {@link #bitBuffer}.
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*/
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private int bitCount;
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/**
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* Set the {@link ByteBuf} from which to read data.
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*/
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void setByteBuf(ByteBuf in) {
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this.in = in;
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}
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/**
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* Reads up to 32 bits from the {@link ByteBuf}.
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* @param count The number of bits to read (maximum {@code 32} as a size of {@code int})
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* @return The bits requested, right-aligned within the integer
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*/
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int readBits(final int count) {
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if (count < 0 || count > 32) {
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throw new IllegalArgumentException("count: " + count + " (expected: 0-32 )");
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}
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int bitCount = this.bitCount;
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long bitBuffer = this.bitBuffer;
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if (bitCount < count) {
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long readData;
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int offset;
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switch (in.readableBytes()) {
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case 1: {
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readData = in.readUnsignedByte();
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offset = 8;
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break;
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}
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case 2: {
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readData = in.readUnsignedShort();
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offset = 16;
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break;
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}
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case 3: {
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readData = in.readUnsignedMedium();
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offset = 24;
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break;
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}
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default: {
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readData = in.readUnsignedInt();
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offset = 32;
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break;
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}
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}
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bitBuffer = bitBuffer << offset | readData;
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bitCount += offset;
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this.bitBuffer = bitBuffer;
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}
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this.bitCount = bitCount -= count;
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return (int) (bitBuffer >>> bitCount & (count != 32 ? (1 << count) - 1 : 0xFFFFFFFFL));
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}
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/**
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* Reads a single bit from the {@link ByteBuf}.
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* @return {@code true} if the bit read was {@code 1}, otherwise {@code false}
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*/
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boolean readBoolean() {
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return readBits(1) != 0;
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}
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/**
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* Reads 32 bits of input as an integer.
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* @return The integer read
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*/
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int readInt() {
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return readBits(32);
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}
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/**
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* Refill the {@link ByteBuf} by one byte.
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*/
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void refill() {
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int readData = in.readUnsignedByte();
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bitBuffer = bitBuffer << 8 | readData;
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bitCount += 8;
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}
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/**
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* Checks that at least one bit is available for reading.
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* @return {@code true} if one bit is available for reading, otherwise {@code false}
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*/
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boolean isReadable() {
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return bitCount > 0 || in.isReadable();
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}
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/**
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* Checks that the specified number of bits available for reading.
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* @param count The number of bits to check
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* @return {@code true} if {@code count} bits are available for reading, otherwise {@code false}
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*/
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boolean hasReadableBits(int count) {
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if (count < 0) {
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throw new IllegalArgumentException("count: " + count + " (expected value greater than 0)");
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}
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return bitCount >= count || (in.readableBytes() << 3 & Integer.MAX_VALUE) >= count - bitCount;
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}
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/**
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* Checks that the specified number of bytes available for reading.
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* @param count The number of bytes to check
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* @return {@code true} if {@code count} bytes are available for reading, otherwise {@code false}
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*/
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boolean hasReadableBytes(int count) {
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if (count < 0 || count > MAX_COUNT_OF_READABLE_BYTES) {
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throw new IllegalArgumentException("count: " + count
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+ " (expected: 0-" + MAX_COUNT_OF_READABLE_BYTES + ')');
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}
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return hasReadableBits(count << 3);
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}
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}
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