121 lines
4.0 KiB
Java
121 lines
4.0 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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* A bit writer that allows the writing of single bit booleans, unary numbers, bit strings
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* of arbitrary length (up to 32 bits), and bit aligned 32-bit integers. A single byte at a
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* time is written to the {@link ByteBuf} when sufficient bits have been accumulated.
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*/
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final class Bzip2BitWriter {
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/**
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* A buffer of bits waiting to be written to the output stream.
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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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* Writes up to 32 bits to the output {@link ByteBuf}.
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* @param count The number of bits to write (maximum {@code 32} as a size of {@code int})
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* @param value The bits to write
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*/
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void writeBits(ByteBuf out, final int count, final long value) {
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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 | value << 64 - count >>> bitCount;
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bitCount += count;
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if (bitCount >= 32) {
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out.writeInt((int) (bitBuffer >>> 32));
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bitBuffer <<= 32;
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bitCount -= 32;
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}
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this.bitBuffer = bitBuffer;
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this.bitCount = bitCount;
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}
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/**
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* Writes a single bit to the output {@link ByteBuf}.
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* @param value The bit to write
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*/
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void writeBoolean(ByteBuf out, final boolean value) {
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int bitCount = this.bitCount + 1;
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long bitBuffer = this.bitBuffer | (value ? 1L << 64 - bitCount : 0L);
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if (bitCount == 32) {
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out.writeInt((int) (bitBuffer >>> 32));
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bitBuffer = 0;
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bitCount = 0;
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}
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this.bitBuffer = bitBuffer;
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this.bitCount = bitCount;
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}
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/**
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* Writes a zero-terminated unary number to the output {@link ByteBuf}.
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* Example of the output for value = 6: {@code 1111110}
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* @param value The number of {@code 1} to write
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*/
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void writeUnary(ByteBuf out, int value) {
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if (value < 0) {
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throw new IllegalArgumentException("value: " + value + " (expected 0 or more)");
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}
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while (value-- > 0) {
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writeBoolean(out, true);
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}
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writeBoolean(out, false);
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}
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/**
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* Writes an integer as 32 bits to the output {@link ByteBuf}.
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* @param value The integer to write
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*/
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void writeInt(ByteBuf out, final int value) {
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writeBits(out, 32, value);
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}
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/**
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* Writes any remaining bits to the output {@link ByteBuf},
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* zero padding to a whole byte as required.
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*/
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void flush(ByteBuf out) {
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final int bitCount = this.bitCount;
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if (bitCount > 0) {
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final long bitBuffer = this.bitBuffer;
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final int shiftToRight = 64 - bitCount;
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if (bitCount <= 8) {
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out.writeByte((int) (bitBuffer >>> shiftToRight << 8 - bitCount));
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} else if (bitCount <= 16) {
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out.writeShort((int) (bitBuffer >>> shiftToRight << 16 - bitCount));
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} else if (bitCount <= 24) {
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out.writeMedium((int) (bitBuffer >>> shiftToRight << 24 - bitCount));
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} else {
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out.writeInt((int) (bitBuffer >>> shiftToRight << 32 - bitCount));
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}
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}
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}
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}
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