io.netty.handler.codec.compression.Bzip2BitWriter Maven / Gradle / Ivy
/*
* Copyright 2014 The Netty Project
*
* The Netty Project licenses this file to you 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:
*
* https://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 io.netty.handler.codec.compression;
import io.netty.buffer.ByteBuf;
/**
* A bit writer that allows the writing of single bit booleans, unary numbers, bit strings
* of arbitrary length (up to 32 bits), and bit aligned 32-bit integers. A single byte at a
* time is written to the {@link ByteBuf} when sufficient bits have been accumulated.
*/
final class Bzip2BitWriter {
/**
* A buffer of bits waiting to be written to the output stream.
*/
private long bitBuffer;
/**
* The number of bits currently buffered in {@link #bitBuffer}.
*/
private int bitCount;
/**
* Writes up to 32 bits to the output {@link ByteBuf}.
* @param count The number of bits to write (maximum {@code 32} as a size of {@code int})
* @param value The bits to write
*/
void writeBits(ByteBuf out, final int count, final long value) {
if (count < 0 || count > 32) {
throw new IllegalArgumentException("count: " + count + " (expected: 0-32)");
}
int bitCount = this.bitCount;
long bitBuffer = this.bitBuffer | value << 64 - count >>> bitCount;
bitCount += count;
if (bitCount >= 32) {
out.writeInt((int) (bitBuffer >>> 32));
bitBuffer <<= 32;
bitCount -= 32;
}
this.bitBuffer = bitBuffer;
this.bitCount = bitCount;
}
/**
* Writes a single bit to the output {@link ByteBuf}.
* @param value The bit to write
*/
void writeBoolean(ByteBuf out, final boolean value) {
int bitCount = this.bitCount + 1;
long bitBuffer = this.bitBuffer | (value ? 1L << 64 - bitCount : 0L);
if (bitCount == 32) {
out.writeInt((int) (bitBuffer >>> 32));
bitBuffer = 0;
bitCount = 0;
}
this.bitBuffer = bitBuffer;
this.bitCount = bitCount;
}
/**
* Writes a zero-terminated unary number to the output {@link ByteBuf}.
* Example of the output for value = 6: {@code 1111110}
* @param value The number of {@code 1} to write
*/
void writeUnary(ByteBuf out, int value) {
if (value < 0) {
throw new IllegalArgumentException("value: " + value + " (expected 0 or more)");
}
while (value-- > 0) {
writeBoolean(out, true);
}
writeBoolean(out, false);
}
/**
* Writes an integer as 32 bits to the output {@link ByteBuf}.
* @param value The integer to write
*/
void writeInt(ByteBuf out, final int value) {
writeBits(out, 32, value);
}
/**
* Writes any remaining bits to the output {@link ByteBuf},
* zero padding to a whole byte as required.
*/
void flush(ByteBuf out) {
final int bitCount = this.bitCount;
if (bitCount > 0) {
final long bitBuffer = this.bitBuffer;
final int shiftToRight = 64 - bitCount;
if (bitCount <= 8) {
out.writeByte((int) (bitBuffer >>> shiftToRight << 8 - bitCount));
} else if (bitCount <= 16) {
out.writeShort((int) (bitBuffer >>> shiftToRight << 16 - bitCount));
} else if (bitCount <= 24) {
out.writeMedium((int) (bitBuffer >>> shiftToRight << 24 - bitCount));
} else {
out.writeInt((int) (bitBuffer >>> shiftToRight << 32 - bitCount));
}
}
}
}