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Java example source code file (Bzip2MoveToFrontTable.java)

This example Java source code file (Bzip2MoveToFrontTable.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

bzip2movetofronttable

The Bzip2MoveToFrontTable.java Java example source code

/*
 * 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:
 *
 *   http://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;

/**
 * A 256 entry Move To Front transform.
 */
final class Bzip2MoveToFrontTable {
    /**
     * The Move To Front list.
     */
    private final byte[] mtf = {
         0,    1,   2,   3,   4,   5,   6,   7,   8,   9,  10,  11,  12,  13,  14,  15,
         16,  17,  18,  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,  29,  30,  31,
         32,  33,  34,  35,  36,  37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,
         48,  49,  50,  51,  52,  53,  54,  55,  56,  57,  58,  59,  60,  61,  62,  63,
         64,  65,  66,  67,  68,  69,  70,  71,  72,  73,  74,  75,  76,  77,  78,  79,
         80,  81,  82,  83,  84,  85,  86,  87,  88,  89,  90,  91,  92,  93,  94,  95,
         96,  97,  98,  99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111,
        112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127,
        (byte) 128, (byte) 129, (byte) 130, (byte) 131, (byte) 132, (byte) 133, (byte) 134, (byte) 135,
        (byte) 136, (byte) 137, (byte) 138, (byte) 139, (byte) 140, (byte) 141, (byte) 142, (byte) 143,
        (byte) 144, (byte) 145, (byte) 146, (byte) 147, (byte) 148, (byte) 149, (byte) 150, (byte) 151,
        (byte) 152, (byte) 153, (byte) 154, (byte) 155, (byte) 156, (byte) 157, (byte) 158, (byte) 159,
        (byte) 160, (byte) 161, (byte) 162, (byte) 163, (byte) 164, (byte) 165, (byte) 166, (byte) 167,
        (byte) 168, (byte) 169, (byte) 170, (byte) 171, (byte) 172, (byte) 173, (byte) 174, (byte) 175,
        (byte) 176, (byte) 177, (byte) 178, (byte) 179, (byte) 180, (byte) 181, (byte) 182, (byte) 183,
        (byte) 184, (byte) 185, (byte) 186, (byte) 187, (byte) 188, (byte) 189, (byte) 190, (byte) 191,
        (byte) 192, (byte) 193, (byte) 194, (byte) 195, (byte) 196, (byte) 197, (byte) 198, (byte) 199,
        (byte) 200, (byte) 201, (byte) 202, (byte) 203, (byte) 204, (byte) 205, (byte) 206, (byte) 207,
        (byte) 208, (byte) 209, (byte) 210, (byte) 211, (byte) 212, (byte) 213, (byte) 214, (byte) 215,
        (byte) 216, (byte) 217, (byte) 218, (byte) 219, (byte) 220, (byte) 221, (byte) 222, (byte) 223,
        (byte) 224, (byte) 225, (byte) 226, (byte) 227, (byte) 228, (byte) 229, (byte) 230, (byte) 231,
        (byte) 232, (byte) 233, (byte) 234, (byte) 235, (byte) 236, (byte) 237, (byte) 238, (byte) 239,
        (byte) 240, (byte) 241, (byte) 242, (byte) 243, (byte) 244, (byte) 245, (byte) 246, (byte) 247,
        (byte) 248, (byte) 249, (byte) 250, (byte) 251, (byte) 252, (byte) 253, (byte) 254, (byte) 255
    };

    /**
     * Moves a value to the head of the MTF list (forward Move To Front transform).
     * @param value The value to move
     * @return The position the value moved from
     */
    int valueToFront(final byte value) {
        int index = 0;
        byte temp = mtf[0];
        if (value != temp) {
            mtf[0] = value;
            while (value != temp) {
                index++;
                final byte temp2 = temp;
                temp = mtf[index];
                mtf[index] = temp2;
            }
        }
        return index;
    }

    /**
     * Gets the value from a given index and moves it to the front of the MTF list (inverse Move To Front transform).
     * @param index The index to move
     * @return The value at the given index
     */
    byte indexToFront(final int index) {
        final byte value = mtf[index];
        System.arraycopy(mtf, 0, mtf, 1, index);
        mtf[0] = value;

        return value;
    }
}

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