Snappy.java — netty Source File

Source Code

/*
 * Copyright 2012 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;
import io.netty.util.concurrent.FastThreadLocal;
import io.netty.util.internal.MathUtil;
import io.netty.util.internal.SystemPropertyUtil;

import java.util.Arrays;

/**
 * Uncompresses an input {@link ByteBuf} encoded with Snappy compression into an
 * output {@link ByteBuf}.
 * <p>
 * See <a href="https://github.com/google/snappy/blob/master/format_description.txt">snappy format</a>.
 */
public final class Snappy {

    private static final int MAX_HT_SIZE = 1 << 14;
    private static final int MIN_COMPRESSIBLE_BYTES = 15;

    // used as a return value to indicate that we haven't yet read our full preamble
    private static final int PREAMBLE_NOT_FULL = -1;
    private static final int NOT_ENOUGH_INPUT = -1;

    // constants for the tag types
    private static final int LITERAL = 0;
    private static final int COPY_1_BYTE_OFFSET = 1;
    private static final int COPY_2_BYTE_OFFSET = 2;
    private static final int COPY_4_BYTE_OFFSET = 3;

    // Hash table used to compress, shared between subsequent call to .encode()
    private static final FastThreadLocal<short[]> HASH_TABLE = new FastThreadLocal<short[]>();

    private static final boolean DEFAULT_REUSE_HASHTABLE =
            SystemPropertyUtil.getBoolean("io.netty.handler.codec.compression.snappy.reuseHashTable", false);

    public Snappy() {
        this(DEFAULT_REUSE_HASHTABLE);
    }

    Snappy(boolean reuseHashtable) {
        this.reuseHashtable = reuseHashtable;
    }

    public static Snappy withHashTableReuse() {
// ... (664 more lines)