/*

   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF 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 org.apache.batik.ext.awt.image.codec.tiff;

/**
 *
 * @version $Id$
 */
class TIFFFaxDecoder {

    private int bitPointer, bytePointer;
    private byte[] data;
    private int w, h;
    private int fillOrder;

    // Data structures needed to store changing elements for the previous
    // and the current scanline
    private int changingElemSize = 0;
    private int[] prevChangingElems;
    private int[] currChangingElems;

    // Element at which to start search in getNextChangingElement
    private int lastChangingElement = 0;

    private int compression = 2;

    // Variables set by T4Options
    private int uncompressedMode = 0;
    private int fillBits = 0;
    private int oneD;

    static int[] table1 = {
        0x00, // 0 bits are left in first byte - SHOULD NOT HAPPEN
        0x01, // 1 bits are left in first byte
        0x03, // 2 bits are left in first byte
        0x07, // 3 bits are left in first byte
        0x0f, // 4 bits are left in first byte
        0x1f, // 5 bits are left in first byte
        0x3f, // 6 bits are left in first byte
        0x7f, // 7 bits are left in first byte
        0xff  // 8 bits are left in first byte
    };

    static int[] table2 = {
        0x00, // 0
        0x80, // 1
        0xc0, // 2
        0xe0, // 3
        0xf0, // 4
        0xf8, // 5
        0xfc, // 6
        0xfe, // 7
        0xff  // 8
    };

    // Table to be used when fillOrder = 2, for flipping bytes.
    static byte[] flipTable = {
         0,  -128,    64,   -64,    32,   -96,    96,   -32,
        16,  -112,    80,   -48,    48,   -80,   112,   -16,
         8,  -120,    72,   -56,    40,   -88,   104,   -24,
        24,  -104,    88,   -40,    56,   -72,   120,    -8,
         4,  -124,    68,   -60,    36,   -92,   100,   -28,
        20,  -108,    84,   -44,    52,   -76,   116,   -12,
        12,  -116,    76,   -52,    44,   -84,   108,   -20,
        28,  -100,    92,   -36,    60,   -68,   124,    -4,
         2,  -126,    66,   -62,    34,   -94,    98,   -30,
        18,  -110,    82,   -46,    50,   -78,   114,   -14,
        10,  -118,    74,   -54,    42,   -86,   106,   -22,
        26,  -102,    90,   -38,    58,   -70,   122,    -6,
         6,  -122,    70,   -58,    38,   -90,   102,   -26,
        22,  -106,    86,   -42,    54,   -74,   118,   -10,
        14,  -114,    78,   -50,    46,   -82,   110,   -18,
        30,   -98,    94,   -34,    62,   -66,   126,    -2,
         1,  -127,    65,   -63,    33,   -95,    97,   -31,
        17,  -111,    81,   -47,    49,   -79,   113,   -15,
         9,  -119,    73,   -55,    41,   -87,   105,   -23,
        25,  -103,    89,   -39,    57,   -71,   121,    -7,
         5,  -123,    69,   -59,    37,   -91,   101,   -27,
        21,  -107,    85,   -43,    53,   -75,   117,   -11,
        13,  -115,    77,   -51,    45,   -83,   109,   -19,
        29,   -99,    93,   -35,    61,   -67,   125,    -3,
         3,  -125,    67,   -61,    35,   -93,    99,   -29,
        19,  -109,    83,   -45,    51,   -77,   115,   -13,
        11,  -117,    75,   -53,    43,   -85,   107,   -21,
        27,  -101,    91,   -37,    59,   -69,   123,    -5,
         7,  -121,    71,   -57,    39,   -89,   103,   -25,
        23,  -105,    87,   -41,    55,   -73,   119,    -9,
        15,  -113,    79,   -49,    47,   -81,   111,   -17,
        31,   -97,    95,   -33,    63,   -65,   127,    -1,
    };

    // The main 10 bit white runs lookup table
    static short[] white = {
        // 0 - 7
        6430,   6400,   6400,   6400,   3225,   3225,   3225,   3225,
        // 8 - 15
        944,    944,    944,    944,    976,    976,    976,    976,
        // 16 - 23
        1456,   1456,   1456,   1456,   1488,   1488,   1488,   1488,
        // 24 - 31
        718,    718,    718,    718,    718,    718,    718,    718,
        // 32 - 39
        750,    750,    750,    750,    750,    750,    750,    750,
        // 40 - 47
        1520,   1520,   1520,   1520,   1552,   1552,   1552,   1552,
        // 48 - 55
        428,    428,    428,    428,    428,    428,    428,    428,
        // 56 - 63
        428,    428,    428,    428,    428,    428,    428,    428,
        // 64 - 71
        654,    654,    654,    654,    654,    654,    654,    654,
        // 72 - 79
        1072,   1072,   1072,   1072,   1104,   1104,   1104,   1104,
        // 80 - 87
        1136,   1136,   1136,   1136,   1168,   1168,   1168,   1168,
        // 88 - 95
        1200,   1200,   1200,   1200,   1232,   1232,   1232,   1232,
        // 96 - 103
        622,    622,    622,    622,    622,    622,    622,    622,
        // 104 - 111
        1008,   1008,   1008,   1008,   1040,   1040,   1040,   1040,
        // 112 - 119
        44,     44,     44,     44,     44,     44,     44,     44,
        // 120 - 127
        44,     44,     44,     44,     44,     44,     44,     44,
        // 128 - 135
        396,    396,    396,    396,    396,    396,    396,    396,
        // 136 - 143
        396,    396,    396,    396,    396,    396,    396,    396,
        // 144 - 151
        1712,   1712,   1712,   1712,   1744,   1744,   1744,   1744,
        // 152 - 159
        846,    846,    846,    846,    846,    846,    846,    846,
        // 160 - 167
        1264,   1264,   1264,   1264,   1296,   1296,   1296,   1296,
        // 168 - 175
        1328,   1328,   1328,   1328,   1360,   1360,   1360,   1360,
        // 176 - 183
        1392,   1392,   1392,   1392,   1424,   1424,   1424,   1424,
        // 184 - 191
        686,    686,    686,    686,    686,    686,    686,    686,
        // 192 - 199
        910,    910,    910,    910,    910,    910,    910,    910,
        // 200 - 207
        1968,   1968,   1968,   1968,   2000,   2000,   2000,   2000,
        // 208 - 215
        2032,   2032,   2032,   2032,     16,     16,     16,     16,
        // 216 - 223
        10257,  10257,  10257,  10257,  12305,  12305,  12305,  12305,
        // 224 - 231
        330,    330,    330,    330,    330,    330,    330,    330,
        // 232 - 239
        330,    330,    330,    330,    330,    330,    330,    330,
        // 240 - 247
        330,    330,    330,    330,    330,    330,    330,    330,
        // 248 - 255
        330,    330,    330,    330,    330,    330,    330,    330,
        // 256 - 263
        362,    362,    362,    362,    362,    362,    362,    362,
        // 264 - 271
        362,    362,    362,    362,    362,    362,    362,    362,
        // 272 - 279
        362,    362,    362,    362,    362,    362,    362,    362,
        // 280 - 287
        362,    362,    362,    362,    362,    362,    362,    362,
        // 288 - 295
        878,    878,    878,    878,    878,    878,    878,    878,
        // 296 - 303
        1904,   1904,   1904,   1904,   1936,   1936,   1936,   1936,
        // 304 - 311
        -18413, -18413, -16365, -16365, -14317, -14317, -10221, -10221,
        // 312 - 319
        590,    590,    590,    590,    590,    590,    590,    590,
        // 320 - 327
        782,    782,    782,    782,    782,    782,    782,    782,
        // 328 - 335
        1584,   1584,   1584,   1584,   1616,   1616,   1616,   1616,
        // 336 - 343
        1648,   1648,   1648,   1648,   1680,   1680,   1680,   1680,
        // 344 - 351
        814,    814,    814,    814,    814,    814,    814,    814,
        // 352 - 359
        1776,   1776,   1776,   1776,   1808,   1808,   1808,   1808,
        // 360 - 367
        1840,   1840,   1840,   1840,   1872,   1872,   1872,   1872,
        // 368 - 375
        6157,   6157,   6157,   6157,   6157,   6157,   6157,   6157,
        // 376 - 383
        6157,   6157,   6157,   6157,   6157,   6157,   6157,   6157,
        // 384 - 391
        -12275, -12275, -12275, -12275, -12275, -12275, -12275, -12275,
        // 392 - 399
        -12275, -12275, -12275, -12275, -12275, -12275, -12275, -12275,
        // 400 - 407
        14353,  14353,  14353,  14353,  16401,  16401,  16401,  16401,
        // 408 - 415
        22547,  22547,  24595,  24595,  20497,  20497,  20497,  20497,
        // 416 - 423
        18449,  18449,  18449,  18449,  26643,  26643,  28691,  28691,
        // 424 - 431
        30739,  30739, -32749, -32749, -30701, -30701, -28653, -28653,
        // 432 - 439
        -26605, -26605, -24557, -24557, -22509, -22509, -20461, -20461,
        // 440 - 447
        8207,   8207,   8207,   8207,   8207,   8207,   8207,   8207,
        // 448 - 455
        72,     72,     72,     72,     72,     72,     72,     72,
        // 456 - 463
        72,     72,     72,     72,     72,     72,     72,     72,
        // 464 - 471
        72,     72,     72,     72,     72,     72,     72,     72,
        // 472 - 479
        72,     72,     72,     72,     72,     72,     72,     72,
        // 480 - 487
        72,     72,     72,     72,     72,     72,     72,     72,
        // 488 - 495
        72,     72,     72,     72,     72,     72,     72,     72,
        // 496 - 503
        72,     72,     72,     72,     72,     72,     72,     72,
        // 504 - 511
        72,     72,     72,     72,     72,     72,     72,     72,
        // 512 - 519
        104,    104,    104,    104,    104,    104,    104,    104,
        // 520 - 527
        104,    104,    104,    104,    104,    104,    104,    104,
        // 528 - 535
        104,    104,    104,    104,    104,    104,    104,    104,
        // 536 - 543
        104,    104,    104,    104,    104,    104,    104,    104,
        // 544 - 551
        104,    104,    104,    104,    104,    104,    104,    104,
        // 552 - 559
        104,    104,    104,    104,    104,    104,    104,    104,
        // 560 - 567
        104,    104,    104,    104,    104,    104,    104,    104,
        // 568 - 575
        104,    104,    104,    104,    104,    104,    104,    104,
        // 576 - 583
        4107,   4107,   4107,   4107,   4107,   4107,   4107,   4107,
        // 584 - 591
        4107,   4107,   4107,   4107,   4107,   4107,   4107,   4107,
        // 592 - 599
        4107,   4107,   4107,   4107,   4107,   4107,   4107,   4107,
        // 600 - 607
        4107,   4107,   4107,   4107,   4107,   4107,   4107,   4107,
        // 608 - 615
        266,    266,    266,    266,    266,    266,    266,    266,
        // 616 - 623
        266,    266,    266,    266,    266,    266,    266,    266,
        // 624 - 631
        266,    266,    266,    266,    266,    266,    266,    266,
        // 632 - 639
        266,    266,    266,    266,    266,    266,    266,    266,
        // 640 - 647
        298,    298,    298,    298,    298,    298,    298,    298,
        // 648 - 655
        298,    298,    298,    298,    298,    298,    298,    298,
        // 656 - 663
        298,    298,    298,    298,    298,    298,    298,    298,
        // 664 - 671
        298,    298,    298,    298,    298,    298,    298,    298,
        // 672 - 679
        524,    524,    524,    524,    524,    524,    524,    524,
        // 680 - 687
        524,    524,    524,    524,    524,    524,    524,    524,
        // 688 - 695
        556,    556,    556,    556,    556,    556,    556,    556,
        // 696 - 703
        556,    556,    556,    556,    556,    556,    556,    556,
        // 704 - 711
        136,    136,    136,    136,    136,    136,    136,    136,
        // 712 - 719
        136,    136,    136,    136,    136,    136,    136,    136,
        // 720 - 727
        136,    136,    136,    136,    136,    136,    136,    136,
        // 728 - 735
        136,    136,    136,    136,    136,    136,    136,    136,
        // 736 - 743
        136,    136,    136,    136,    136,    136,    136,    136,
        // 744 - 751
        136,    136,    136,    136,    136,    136,    136,    136,
        // 752 - 759
        136,    136,    136,    136,    136,    136,    136,    136,
        // 760 - 767
        136,    136,    136,    136,    136,    136,    136,    136,
        // 768 - 775
        168,    168,    168,    168,    168,    168,    168,    168,
        // 776 - 783
        168,    168,    168,    168,    168,    168,    168,    168,
        // 784 - 791
        168,    168,    168,    168,    168,    168,    168,    168,
        // 792 - 799
        168,    168,    168,    168,    168,    168,    168,    168,
        // 800 - 807
        168,    168,    168,    168,    168,    168,    168,    168,
        // 808 - 815
        168,    168,    168,    168,    168,    168,    168,    168,
        // 816 - 823
        168,    168,    168,    168,    168,    168,    168,    168,
        // 824 - 831
        168,    168,    168,    168,    168,    168,    168,    168,
        // 832 - 839
        460,    460,    460,    460,    460,    460,    460,    460,
        // 840 - 847
        460,    460,    460,    460,    460,    460,    460,    460,
        // 848 - 855
        492,    492,    492,    492,    492,    492,    492,    492,
        // 856 - 863
        492,    492,    492,    492,    492,    492,    492,    492,
        // 864 - 871
        2059,   2059,   2059,   2059,   2059,   2059,   2059,   2059,
        // 872 - 879
        2059,   2059,   2059,   2059,   2059,   2059,   2059,   2059,
        // 880 - 887
        2059,   2059,   2059,   2059,   2059,   2059,   2059,   2059,
        // 888 - 895
        2059,   2059,   2059,   2059,   2059,   2059,   2059,   2059,
        // 896 - 903
        200,    200,    200,    200,    200,    200,    200,    200,
        // 904 - 911
        200,    200,    200,    200,    200,    200,    200,    200,
        // 912 - 919
        200,    200,    200,    200,    200,    200,    200,    200,
        // 920 - 927
        200,    200,    200,    200,    200,    200,    200,    200,
        // 928 - 935
        200,    200,    200,    200,    200,    200,    200,    200,
        // 936 - 943
        200,    200,    200,    200,    200,    200,    200,    200,
        // 944 - 951
        200,    200,    200,    200,    200,    200,    200,    200,
        // 952 - 959
        200,    200,    200,    200,    200,    200,    200,    200,
        // 960 - 967
        232,    232,    232,    232,    232,    232,    232,    232,
        // 968 - 975
        232,    232,    232,    232,    232,    232,    232,    232,
        // 976 - 983
        232,    232,    232,    232,    232,    232,    232,    232,
        // 984 - 991
        232,    232,    232,    232,    232,    232,    232,    232,
        // 992 - 999
        232,    232,    232,    232,    232,    232,    232,    232,
        // 1000 - 1007
        232,    232,    232,    232,    232,    232,    232,    232,
        // 1008 - 1015
        232,    232,    232,    232,    232,    232,    232,    232,
        // 1016 - 1023
        232,    232,    232,    232,    232,    232,    232,    232,
    };

    // Additional make up codes for both White and Black runs
    static short[] additionalMakeup = {
        28679,  28679,  31752,  (short)32777,
        (short)33801,  (short)34825,  (short)35849,  (short)36873,
        (short)29703,  (short)29703,  (short)30727,  (short)30727,
        (short)37897,  (short)38921,  (short)39945,  (short)40969
    };

    // Initial black run look up table, uses the first 4 bits of a code
    static short[] initBlack = {
        // 0 - 7
        3226,  6412,    200,    168,    38,     38,    134,    134,
        // 8 - 15
        100,    100,    100,    100,    68,     68,     68,     68
    };

    //
    static short[] twoBitBlack = {292, 260, 226, 226};   // 0 - 3

    // Main black run table, using the last 9 bits of possible 13 bit code
    static short[] black = {
        // 0 - 7
        62,     62,     30,     30,     0,      0,      0,      0,
        // 8 - 15
        0,      0,      0,      0,      0,      0,      0,      0,
        // 16 - 23
        0,      0,      0,      0,      0,      0,      0,      0,
        // 24 - 31
        0,      0,      0,      0,      0,      0,      0,      0,
        // 32 - 39
        3225,   3225,   3225,   3225,   3225,   3225,   3225,   3225,
        // 40 - 47
        3225,   3225,   3225,   3225,   3225,   3225,   3225,   3225,
        // 48 - 55
        3225,   3225,   3225,   3225,   3225,   3225,   3225,   3225,
        // 56 - 63
        3225,   3225,   3225,   3225,   3225,   3225,   3225,   3225,
        // 64 - 71
        588,    588,    588,    588,    588,    588,    588,    588,
        // 72 - 79
        1680,   1680,  20499,  22547,  24595,  26643,   1776,   1776,
        // 80 - 87
        1808,   1808, -24557, -22509, -20461, -18413,   1904,   1904,
        // 88 - 95
        1936,   1936, -16365, -14317,    782,    782,    782,    782,
        // 96 - 103
        814,    814,    814,    814, -12269, -10221,  10257,  10257,
        // 104 - 111
        12305,  12305,  14353,  14353,  16403,  18451,   1712,   1712,
        // 112 - 119
        1744,   1744,  28691,  30739, -32749, -30701, -28653, -26605,
        // 120 - 127
        2061,   2061,   2061,   2061,   2061,   2061,   2061,   2061,
        // 128 - 135
        424,    424,    424,    424,    424,    424,    424,    424,
        // 136 - 143
        424,    424,    424,    424,    424,    424,    424,    424,
        // 144 - 151
        424,    424,    424,    424,    424,    424,    424,    424,
        // 152 - 159
        424,    424,    424,    424,    424,    424,    424,    424,
        // 160 - 167
        750,    750,    750,    750,   1616,   1616,   1648,   1648,
        // 168 - 175
        1424,   1424,   1456,   1456,   1488,   1488,   1520,   1520,
        // 176 - 183
        1840,   1840,   1872,   1872,   1968,   1968,   8209,   8209,
        // 184 - 191
        524,    524,    524,    524,    524,    524,    524,    524,
        // 192 - 199
        556,    556,    556,    556,    556,    556,    556,    556,
        // 200 - 207
        1552,   1552,   1584,   1584,   2000,   2000,   2032,   2032,
        // 208 - 215
        976,    976,   1008,   1008,   1040,   1040,   1072,   1072,
        // 216 - 223
        1296,   1296,   1328,   1328,    718,    718,    718,    718,
        // 224 - 231
        456,    456,    456,    456,    456,    456,    456,    456,
        // 232 - 239
        456,    456,    456,    456,    456,    456,    456,    456,
        // 240 - 247
        456,    456,    456,    456,    456,    456,    456,    456,
        // 248 - 255
        456,    456,    456,    456,    456,    456,    456,    456,
        // 256 - 263
        326,    326,    326,    326,    326,    326,    326,    326,
        // 264 - 271
        326,    326,    326,    326,    326,    326,    326,    326,
        // 272 - 279
        326,    326,    326,    326,    326,    326,    326,    326,
        // 280 - 287
        326,    326,    326,    326,    326,    326,    326,    326,
        // 288 - 295
        326,    326,    326,    326,    326,    326,    326,    326,
        // 296 - 303
        326,    326,    326,    326,    326,    326,    326,    326,
        // 304 - 311
        326,    326,    326,    326,    326,    326,    326,    326,
        // 312 - 319
        326,    326,    326,    326,    326,    326,    326,    326,
        // 320 - 327
        358,    358,    358,    358,    358,    358,    358,    358,
        // 328 - 335
        358,    358,    358,    358,    358,    358,    358,    358,
        // 336 - 343
        358,    358,    358,    358,    358,    358,    358,    358,
        // 344 - 351
        358,    358,    358,    358,    358,    358,    358,    358,
        // 352 - 359
        358,    358,    358,    358,    358,    358,    358,    358,
        // 360 - 367
        358,    358,    358,    358,    358,    358,    358,    358,
        // 368 - 375
        358,    358,    358,    358,    358,    358,    358,    358,
        // 376 - 383
        358,    358,    358,    358,    358,    358,    358,    358,
        // 384 - 391
        490,    490,    490,    490,    490,    490,    490,    490,
        // 392 - 399
        490,    490,    490,    490,    490,    490,    490,    490,
        // 400 - 407
        4113,   4113,   6161,   6161,    848,    848,    880,    880,
        // 408 - 415
        912,    912,    944,    944,    622,    622,    622,    622,
        // 416 - 423
        654,    654,    654,    654,   1104,   1104,   1136,   1136,
        // 424 - 431
        1168,   1168,   1200,   1200,   1232,   1232,   1264,   1264,
        // 432 - 439
        686,    686,    686,    686,   1360,   1360,   1392,   1392,
        // 440 - 447
        12,     12,     12,     12,     12,     12,     12,     12,
        // 448 - 455
        390,    390,    390,    390,    390,    390,    390,    390,
        // 456 - 463
        390,    390,    390,    390,    390,    390,    390,    390,
        // 464 - 471
        390,    390,    390,    390,    390,    390,    390,    390,
        // 472 - 479
        390,    390,    390,    390,    390,    390,    390,    390,
        // 480 - 487
        390,    390,    390,    390,    390,    390,    390,    390,
        // 488 - 495
        390,    390,    390,    390,    390,    390,    390,    390,
        // 496 - 503
        390,    390,    390,    390,    390,    390,    390,    390,
        // 504 - 511
        390,    390,    390,    390,    390,    390,    390,    390,
    };

    static byte[] twoDCodes = {
        // 0 - 7
        80,     88,     23,     71,     30,     30,     62,     62,
        // 8 - 15
        4,      4,      4,      4,      4,      4,      4,      4,
        // 16 - 23
        11,     11,     11,     11,     11,     11,     11,     11,
        // 24 - 31
        11,     11,     11,     11,     11,     11,     11,     11,
        // 32 - 39
        35,     35,     35,     35,     35,     35,     35,     35,
        // 40 - 47
        35,     35,     35,     35,     35,     35,     35,     35,
        // 48 - 55
        51,     51,     51,     51,     51,     51,     51,     51,
        // 56 - 63
        51,     51,     51,     51,     51,     51,     51,     51,
        // 64 - 71
        41,     41,     41,     41,     41,     41,     41,     41,
        // 72 - 79
        41,     41,     41,     41,     41,     41,     41,     41,
        // 80 - 87
        41,     41,     41,     41,     41,     41,     41,     41,
        // 88 - 95
        41,     41,     41,     41,     41,     41,     41,     41,
        // 96 - 103
        41,     41,     41,     41,     41,     41,     41,     41,
        // 104 - 111
        41,     41,     41,     41,     41,     41,     41,     41,
        // 112 - 119
        41,     41,     41,     41,     41,     41,     41,     41,
        // 120 - 127
        41,     41,     41,     41,     41,     41,     41,     41,
    };

    /**
     * @param fillOrder   The fill order of the compressed data bytes.
     */
    public TIFFFaxDecoder(int fillOrder, int w, int h) {
        this.fillOrder = fillOrder;
        this.w = w;
        this.h = h;

        this.bitPointer = 0;
        this.bytePointer = 0;
        this.prevChangingElems = new int[w];
        this.currChangingElems = new int[w];
    }

    // One-dimensional decoding methods

    public void decode1D(byte[] buffer, byte[] compData,
                         int startX, int height) {
        this.data = compData;

        int lineOffset = 0;
        int scanlineStride = (w + 7)/8;

        bitPointer = 0;
        bytePointer = 0;

        for (int i = 0; i < height; i++) {
            decodeNextScanline(buffer, lineOffset, startX);
            lineOffset += scanlineStride;
        }
    }

    public void decodeNextScanline(byte[] buffer,
                                   int lineOffset, int bitOffset) {
        int bits = 0, code = 0, isT = 0;
        int current, entry, twoBits;
        boolean isWhite = true;

        // Initialize starting of the changing elements array
        changingElemSize = 0;

        // While scanline not complete
        while (bitOffset < w) {
            while (isWhite) {
                // White run
                current = nextNBits(10);
                entry = white[current];

                // Get the 3 fields from the entry
                isT = entry & 0x0001;
                bits = (entry >>> 1) & 0x0f;

                if (bits == 12) {          // Additional Make up code
                    // Get the next 2 bits
                    twoBits = nextLesserThan8Bits(2);
                    // Consolidate the 2 new bits and last 2 bits into 4 bits
                    current = ((current << 2) & 0x000c) | twoBits;
                    entry = additionalMakeup[current];
                    bits = (entry >>> 1) & 0x07;     // 3 bits 0000 0111
                    code  = (entry >>> 4) & 0x0fff;  // 12 bits
                    bitOffset += code; // Skip white run

                    updatePointer(4 - bits);
                } else if (bits == 0) {     // ERROR
                    throw new Error("TIFFFaxDecoder0");
                } else if (bits == 15) {    // EOL
                    throw new Error("TIFFFaxDecoder1");
                } else {
                    // 11 bits - 0000 0111 1111 1111 = 0x07ff
                    code = (entry >>> 5) & 0x07ff;
                    bitOffset += code;

                    updatePointer(10 - bits);
                    if (isT == 0) {
                        isWhite = false;
                        currChangingElems[changingElemSize++] = bitOffset;
                    }
                }
            }

            // Check whether this run completed one width, if so
            // advance to next byte boundary for compression = 2.
            if (bitOffset == w) {
                if (compression == 2) {
                    advancePointer();
                }
                break;
            }

            while ( ! isWhite ) {
                // Black run
                current = nextLesserThan8Bits(4);
                entry = initBlack[current];

                // Get the 3 fields from the entry
                isT = entry & 0x0001;
                bits = (entry >>> 1) & 0x000f;
                code = (entry >>> 5) & 0x07ff;

                if (code == 100) {
                    current = nextNBits(9);
                    entry = black[current];

                    // Get the 3 fields from the entry
                    isT = entry & 0x0001;
                    bits = (entry >>> 1) & 0x000f;
                    code = (entry >>> 5) & 0x07ff;

                    if (bits == 12) {
                        // Additional makeup codes
                        updatePointer(5);
                        current = nextLesserThan8Bits(4);
                        entry = additionalMakeup[current];
                        bits = (entry >>> 1) & 0x07;     // 3 bits 0000 0111
                        code  = (entry >>> 4) & 0x0fff;  // 12 bits

                        setToBlack(buffer, lineOffset, bitOffset, code);
                        bitOffset += code;

                        updatePointer(4 - bits);
                    } else if (bits == 15) {
                        // EOL code
                        throw new Error("TIFFFaxDecoder2");
                    } else {
                        setToBlack(buffer, lineOffset, bitOffset, code);
                        bitOffset += code;

                        updatePointer(9 - bits);
                        if (isT == 0) {
                            isWhite = true;
                            currChangingElems[changingElemSize++] = bitOffset;
                        }
                    }
                } else if (code == 200) {
                    // Is a Terminating code
                    current = nextLesserThan8Bits(2);
                    entry = twoBitBlack[current];
                    code = (entry >>> 5) & 0x07ff;
                    bits = (entry >>> 1) & 0x0f;

                    setToBlack(buffer, lineOffset, bitOffset, code);
                    bitOffset += code;

                    updatePointer(2 - bits);
                    isWhite = true;
                    currChangingElems[changingElemSize++] = bitOffset;
                } else {
                    // Is a Terminating code
                    setToBlack(buffer, lineOffset, bitOffset, code);
                    bitOffset += code;

                    updatePointer(4 - bits);
                    isWhite = true;
                    currChangingElems[changingElemSize++] = bitOffset;
                }
            }

            // Check whether this run completed one width
            if (bitOffset == w) {
                if (compression == 2) {
                    advancePointer();
                }
                break;
            }
        }

        currChangingElems[changingElemSize++] = bitOffset;
    }

    // Two-dimensional decoding methods

    public void decode2D(byte[] buffer,
                         byte[] compData,
                         int startX,
                         int height,
                         long tiffT4Options) {
        this.data = compData;
        compression = 3;

        bitPointer = 0;
        bytePointer = 0;

        int scanlineStride = (w + 7)/8;

        int a0, a1, b1, b2;
        int[] b = new int[2];
        int entry, code, bits;
        boolean isWhite;
        int currIndex = 0;
        int[] temp;

        // fillBits - dealt with this in readEOL
        // 1D/2D encoding - dealt with this in readEOL

        // uncompressedMode - haven't dealt with this yet.


        oneD = (int)(tiffT4Options & 0x01);
        uncompressedMode = (int)((tiffT4Options & 0x02) >> 1);
        fillBits = (int)((tiffT4Options & 0x04) >> 2);

        // The data must start with an EOL code
        if (readEOL() != 1) {
            throw new Error("TIFFFaxDecoder3");
        }

        int lineOffset = 0;
        int bitOffset;

        // Then the 1D encoded scanline data will occur, changing elements
        // array gets set.
        decodeNextScanline(buffer, lineOffset, startX);
        lineOffset += scanlineStride;

        for (int lines = 1; lines < height; lines++) {

            // Every line must begin with an EOL followed by a bit which
            // indicates whether the following scanline is 1D or 2D encoded.
            if (readEOL() == 0) {
                // 2D encoded scanline follows

                // Initialize previous scanlines changing elements, and
                // initialize current scanline's changing elements array
                temp = prevChangingElems;
                prevChangingElems = currChangingElems;
                currChangingElems = temp;
                currIndex = 0;

                // a0 has to be set just before the start of this scanline.
                a0 = -1;
                isWhite = true;
                bitOffset = startX;

                lastChangingElement = 0;

                while (bitOffset < w) {
                    // Get the next changing element
                    getNextChangingElement(a0, isWhite, b);

                    b1 = b[0];
                    b2 = b[1];

                    // Get the next seven bits
                    entry = nextLesserThan8Bits(7);

                    // Run these through the 2DCodes table
                    entry = (int)(twoDCodes[entry] & 0xff);

                    // Get the code and the number of bits used up
                    code = (entry & 0x78) >>> 3;
                    bits = entry & 0x07;

                    if (code == 0) {
                        if (!isWhite) {
                            setToBlack(buffer, lineOffset, bitOffset,
                                       b2 - bitOffset);
                        }
                        bitOffset = a0 = b2;

                        // Set pointer to consume the correct number of bits.
                        updatePointer(7 - bits);
                    } else if (code == 1) {
                        // Horizontal
                        updatePointer(7 - bits);

                        // identify the next 2 codes.
                        int number;
                        if (isWhite) {
                            number = decodeWhiteCodeWord();
                            bitOffset += number;
                            currChangingElems[currIndex++] = bitOffset;

                            number = decodeBlackCodeWord();
                            setToBlack(buffer, lineOffset, bitOffset, number);
                            bitOffset += number;
                            currChangingElems[currIndex++] = bitOffset;
                        } else {
                            number = decodeBlackCodeWord();
                            setToBlack(buffer, lineOffset, bitOffset, number);
                            bitOffset += number;
                            currChangingElems[currIndex++] = bitOffset;

                            number = decodeWhiteCodeWord();
                            bitOffset += number;
                            currChangingElems[currIndex++] = bitOffset;
                        }

                        a0 = bitOffset;
                    } else if (code <= 8) {
                        // Vertical
                        a1 = b1 + (code - 5);

                        currChangingElems[currIndex++] = a1;

                        // We write the current color till a1 - 1 pos,
                        // since a1 is where the next color starts
                        if (!isWhite) {
                            setToBlack(buffer, lineOffset, bitOffset,
                                       a1 - bitOffset);
                        }
                        bitOffset = a0 = a1;
                        isWhite = !isWhite;

                        updatePointer(7 - bits);
                    } else {
                        throw new Error("TIFFFaxDecoder4");
                    }
                }

                // Add the changing element beyond the current scanline for the
                // other color too
                currChangingElems[currIndex++] = bitOffset;
                changingElemSize = currIndex;
            } else {
                // 1D encoded scanline follows
                decodeNextScanline(buffer, lineOffset, startX);
            }

            lineOffset += scanlineStride;
        }
    }

    public synchronized void decodeT6(byte[] buffer,
                                      byte[] compData,
                                      int startX,
                                      int height,
                                      long tiffT6Options) {
        this.data = compData;
        compression = 4;

        bitPointer = 0;
        bytePointer = 0;

        int scanlineStride = (w + 7)/8;

        int a0, a1, b1, b2;
        int entry, code, bits;
        boolean isWhite;
        int currIndex;
        int[] temp;

        // Return values from getNextChangingElement
        int[] b = new int[2];

        // uncompressedMode - have written some code for this, but this
        // has not been tested due to lack of test images using this optional

        uncompressedMode = (int)((tiffT6Options & 0x02) >> 1);

        // Local cached reference
        int[] cce = currChangingElems;

        // Assume invisible preceding row of all white pixels and insert
        // both black and white changing elements beyond the end of this
        // imaginary scanline.
        changingElemSize = 0;
        cce[changingElemSize++] = w;
        cce[changingElemSize++] = w;

        int lineOffset = 0;
        int bitOffset;

        for (int lines = 0; lines < height; lines++) {
            // a0 has to be set just before the start of the scanline.
            a0 = -1;
            isWhite = true;

            // Assign the changing elements of the previous scanline to
            // prevChangingElems and start putting this new scanline's
            // changing elements into the currChangingElems.
            temp = prevChangingElems;
            prevChangingElems = currChangingElems;
            cce = currChangingElems = temp;
            currIndex = 0;

            // Start decoding the scanline at startX in the raster
            bitOffset = startX;

            // Reset search start position for getNextChangingElement
            lastChangingElement = 0;

            // Till one whole scanline is decoded
            while (bitOffset < w) {
                // Get the next changing element
                getNextChangingElement(a0, isWhite, b);
                b1 = b[0];
                b2 = b[1];

                // Get the next seven bits
                entry = nextLesserThan8Bits(7);
                // Run these through the 2DCodes table
                entry = (int)(twoDCodes[entry] & 0xff);

                // Get the code and the number of bits used up
                code = (entry & 0x78) >>> 3;
                bits = entry & 0x07;

                if (code == 0) { // Pass
                    // We always assume WhiteIsZero format for fax.
                    if (!isWhite) {
                        setToBlack(buffer, lineOffset, bitOffset,
                                   b2 - bitOffset);
                    }
                    bitOffset = a0 = b2;

                    // Set pointer to only consume the correct number of bits.
                    updatePointer(7 - bits);
                } else if (code == 1) { // Horizontal
                    // Set pointer to only consume the correct number of bits.
                    updatePointer(7 - bits);

                    // identify the next 2 alternating color codes.
                    int number;
                    if (isWhite) {
                        // Following are white and black runs
                        number = decodeWhiteCodeWord();
                        bitOffset += number;
                        cce[currIndex++] = bitOffset;

                        number = decodeBlackCodeWord();
                        setToBlack(buffer, lineOffset, bitOffset, number);
                        bitOffset += number;
                        cce[currIndex++] = bitOffset;
                    } else {
                        // First a black run and then a white run follows
                        number = decodeBlackCodeWord();
                        setToBlack(buffer, lineOffset, bitOffset, number);
                        bitOffset += number;
                        cce[currIndex++] = bitOffset;

                        number = decodeWhiteCodeWord();
                        bitOffset += number;
                        cce[currIndex++] = bitOffset;
                    }

                    a0 = bitOffset;
                } else if (code <= 8) { // Vertical
                    a1 = b1 + (code - 5);
                    cce[currIndex++] = a1;

                    // We write the current color till a1 - 1 pos,
                    // since a1 is where the next color starts
                    if (!isWhite) {
                        setToBlack(buffer, lineOffset, bitOffset,
                                   a1 - bitOffset);
                    }
                    bitOffset = a0 = a1;
                    isWhite = !isWhite;

                    updatePointer(7 - bits);
                } else if (code == 11) {
                    if (nextLesserThan8Bits(3) != 7) {
                        throw new Error("TIFFFaxDecoder5");
                    }

                    int zeros = 0;
                    boolean exit = false;

                    while (!exit) {
                        while (nextLesserThan8Bits(1) != 1) {
                            zeros++;
                        }

                        if (zeros > 5) {
                            // Exit code

                            // Zeros before exit code
                            zeros = zeros - 6;

                            if (!isWhite && (zeros > 0)) {
                                cce[currIndex++] = bitOffset;
                            }

                            // Zeros before the exit code
                            bitOffset += zeros;
                            if (zeros > 0) {
                                // Some zeros have been written
                                isWhite = true;
                            }

                            // Read in the bit which specifies the color of
                            // the following run
                            if (nextLesserThan8Bits(1) == 0) {
                                if (!isWhite) {
                                    cce[currIndex++] = bitOffset;
                                }
                                isWhite = true;
                            } else {
                                if (isWhite) {
                                    cce[currIndex++] = bitOffset;
                                }
                                isWhite = false;
                            }

                            exit = true;
                        }

                        if (zeros == 5) {
                            if (!isWhite) {
                                cce[currIndex++] = bitOffset;
                            }
                            bitOffset += zeros;

                            // Last thing written was white
                            isWhite = true;
                        } else {
                            bitOffset += zeros;

                            cce[currIndex++] = bitOffset;
                            setToBlack(buffer, lineOffset, bitOffset, 1);
                            ++bitOffset;

                            // Last thing written was black
                            isWhite = false;
                        }

                    }
                } else {
                    throw new Error("TIFFFaxDecoder5");
                }
            }

            // Add the changing element beyond the current scanline for the
            // other color too
            cce[currIndex++] = bitOffset;

            // Number of changing elements in this scanline.
            changingElemSize = currIndex;

            lineOffset += scanlineStride;
        }
    }

    private void setToBlack(byte[] buffer,
                            int lineOffset, int bitOffset,
                            int numBits) {
        int bitNum = 8*lineOffset + bitOffset;
        int lastBit = bitNum + numBits;

        int byteNum = bitNum >> 3;

        // Handle bits in first byte
        int shift = bitNum & 0x7;
        if (shift > 0) {
            int maskVal = 1 << (7 - shift);
            byte val = buffer[byteNum];
            while (maskVal > 0 && bitNum < lastBit) {
                val |= maskVal;
                maskVal >>= 1;
                ++bitNum;
            }
            buffer[byteNum] = val;
        }

        // Fill in 8 bits at a time
        byteNum = bitNum >> 3;
        while (bitNum < lastBit - 7) {
            buffer[byteNum++] = (byte)255;
            bitNum += 8;
        }

        // Fill in remaining bits
        while (bitNum < lastBit) {
            byteNum = bitNum >> 3;
            buffer[byteNum] |= 1 << (7 - (bitNum & 0x7));
            ++bitNum;
        }
    }

    // Returns run length
    private int decodeWhiteCodeWord() {
        int current, entry, bits, isT, twoBits, code = -1;
        int runLength = 0;
        boolean isWhite = true;

        while (isWhite) {
            current = nextNBits(10);
            entry = white[current];

            // Get the 3 fields from the entry
            isT = entry & 0x0001;
            bits = (entry >>> 1) & 0x0f;

            if (bits == 12) {           // Additional Make up code
                // Get the next 2 bits
                twoBits = nextLesserThan8Bits(2);
                // Consolidate the 2 new bits and last 2 bits into 4 bits
                current = ((current << 2) & 0x000c) | twoBits;
                entry = additionalMakeup[current];
                bits = (entry >>> 1) & 0x07;     // 3 bits 0000 0111
                code = (entry >>> 4) & 0x0fff;   // 12 bits
                runLength += code;
                updatePointer(4 - bits);
            } else if (bits == 0) {     // ERROR
                throw new Error("TIFFFaxDecoder0");
            } else if (bits == 15) {    // EOL
                throw new Error("TIFFFaxDecoder1");
            } else {
                // 11 bits - 0000 0111 1111 1111 = 0x07ff
                code = (entry >>> 5) & 0x07ff;
                runLength += code;
                updatePointer(10 - bits);
                if (isT == 0) {
                    isWhite = false;
                }
            }
        }

        return runLength;
    }

    // Returns run length
    private int decodeBlackCodeWord() {
        int current, entry, bits, isT, code = -1;
        int runLength = 0;
        boolean isWhite = false;

        while (!isWhite) {
            current = nextLesserThan8Bits(4);
            entry = initBlack[current];

            // Get the 3 fields from the entry
            isT = entry & 0x0001;
            bits = (entry >>> 1) & 0x000f;
            code = (entry >>> 5) & 0x07ff;

            if (code == 100) {
                current = nextNBits(9);
                entry = black[current];

                // Get the 3 fields from the entry
                isT = entry & 0x0001;
                bits = (entry >>> 1) & 0x000f;
                code = (entry >>> 5) & 0x07ff;

                if (bits == 12) {
                    // Additional makeup codes
                    updatePointer(5);
                    current = nextLesserThan8Bits(4);
                    entry = additionalMakeup[current];
                    bits = (entry >>> 1) & 0x07;     // 3 bits 0000 0111
                    code  = (entry >>> 4) & 0x0fff;  // 12 bits
                    runLength += code;

                    updatePointer(4 - bits);
                } else if (bits == 15) {
                    // EOL code
                    throw new Error("TIFFFaxDecoder2");
                } else {
                    runLength += code;
                    updatePointer(9 - bits);
                    if (isT == 0) {
                        isWhite = true;
                    }
                }
            } else if (code == 200) {
                // Is a Terminating code
                current = nextLesserThan8Bits(2);
                entry = twoBitBlack[current];
                code = (entry >>> 5) & 0x07ff;
                runLength += code;
                bits = (entry >>> 1) & 0x0f;
                updatePointer(2 - bits);
                isWhite = true;
            } else {
                // Is a Terminating code
                runLength += code;
                updatePointer(4 - bits);
                isWhite = true;
            }
        }

        return runLength;
    }

    private int readEOL() {
        if (fillBits == 0) {
            if (nextNBits(12) != 1) {
                throw new Error("TIFFFaxDecoder6");
            }
        } else if (fillBits == 1) {

            // First EOL code word xxxx 0000 0000 0001 will occur
            // As many fill bits will be present as required to make
            // the EOL code of 12 bits end on a byte boundary.

            int bitsLeft = 8 - bitPointer;

            if (nextNBits(bitsLeft) != 0) {
                    throw new Error("TIFFFaxDecoder8");
            }

            // If the number of bitsLeft is less than 8, then to have a 12
            // bit EOL sequence, two more bytes are certainly going to be
            // required. The first of them has to be all zeros, so ensure
            // that.
            if (bitsLeft < 4) {
                if (nextNBits(8) != 0) {
                    throw new Error("TIFFFaxDecoder8");
                }
            }

            // There might be a random number of fill bytes with 0s, so
            // loop till the EOL of 0000 0001 is found, as long as all
            // the bytes preceding it are 0's.
            int n;
            while ((n = nextNBits(8)) != 1) {

                // If not all zeros
                if (n != 0) {
                    throw new Error("TIFFFaxDecoder8");
                }
            }
        }

        // If one dimensional encoding mode, then always return 1
        if (oneD == 0) {
            return 1;
        } else {
            // Otherwise for 2D encoding mode,
            // The next one bit signifies 1D/2D encoding of next line.
            return nextLesserThan8Bits(1);
        }
    }

    private void getNextChangingElement(int a0, boolean isWhite, int[] ret) {
        // Local copies of instance variables
        int[] pce = this.prevChangingElems;
        int ces = this.changingElemSize;

        // If the previous match was at an odd element, we still
        // have to search the preceeding element.
        // int start = lastChangingElement & ~0x1;
        int start = lastChangingElement > 0 ? lastChangingElement - 1 : 0;
        if (isWhite) {
            start &= ~0x1; // Search even numbered elements
        } else {
            start |= 0x1; // Search odd numbered elements
        }

        int i = start;
        for (; i < ces; i += 2) {
            int temp = pce[i];
            if (temp > a0) {
                lastChangingElement = i;
                ret[0] = temp;
                break;
            }
        }

        if (i + 1 < ces) {
            ret[1] = pce[i + 1];
        }
    }

    private int nextNBits(int bitsToGet) {
        byte b, next, next2next;
        int l = data.length - 1;
        int bp = this.bytePointer;

        if (fillOrder == 1) {
            b = data[bp];

            if (bp == l) {
                next = 0x00;
                next2next = 0x00;
            } else if ((bp + 1) == l) {
                next = data[bp + 1];
                next2next = 0x00;
            } else {
                next = data[bp + 1];
                next2next = data[bp + 2];
            }
        } else if (fillOrder == 2) {
            b = flipTable[data[bp] & 0xff];

            if (bp == l) {
                next = 0x00;
                next2next = 0x00;
            } else if ((bp + 1) == l) {
                next = flipTable[data[bp + 1] & 0xff];
                next2next = 0x00;
            } else {
                next = flipTable[data[bp + 1] & 0xff];
                next2next = flipTable[data[bp + 2] & 0xff];
            }
        } else {
            throw new Error("TIFFFaxDecoder7");
        }

        int bitsLeft = 8 - bitPointer;
        int bitsFromNextByte = bitsToGet - bitsLeft;
        int bitsFromNext2NextByte = 0;
        if (bitsFromNextByte > 8) {
            bitsFromNext2NextByte = bitsFromNextByte - 8;
            bitsFromNextByte = 8;
        }

        bytePointer++;

        int i1 = (b & table1[bitsLeft]) << (bitsToGet - bitsLeft);
        int i2 = (next & table2[bitsFromNextByte]) >>> (8 - bitsFromNextByte);

        int i3 = 0;
        if (bitsFromNext2NextByte != 0) {
            i2 <<= bitsFromNext2NextByte;
            i3 = (next2next & table2[bitsFromNext2NextByte]) >>>
                (8 - bitsFromNext2NextByte);
            i2 |= i3;
            bytePointer++;
            bitPointer = bitsFromNext2NextByte;
        } else {
            if (bitsFromNextByte == 8) {
                bitPointer = 0;
                bytePointer++;
            } else {
                bitPointer = bitsFromNextByte;
            }
        }

        int i = i1 | i2;
        return i;
    }

    private int nextLesserThan8Bits(int bitsToGet) {
        byte b, next;
        int l = data.length - 1;
        int bp = this.bytePointer;

        if (fillOrder == 1) {
            b = data[bp];
            if (bp == l) {
                next = 0x00;
            } else {
                next = data[bp + 1];
            }
        } else if (fillOrder == 2) {
            b = flipTable[data[bp] & 0xff];
            if (bp == l) {
                next = 0x00;
            } else {
                next = flipTable[data[bp + 1] & 0xff];
            }
        } else {
            throw new Error("TIFFFaxDecoder7");
        }

        int bitsLeft = 8 - bitPointer;
        int bitsFromNextByte = bitsToGet - bitsLeft;

        int shift = bitsLeft - bitsToGet;
        int i1, i2;
        if (shift >= 0) {
            i1 = (b & table1[bitsLeft]) >>> shift;
            bitPointer += bitsToGet;
            if (bitPointer == 8) {
                bitPointer = 0;
                bytePointer++;
            }
        } else {
            i1 = (b & table1[bitsLeft]) << (-shift);
            i2 = (next & table2[bitsFromNextByte]) >>> (8 - bitsFromNextByte);

            i1 |= i2;
            bytePointer++;
            bitPointer = bitsFromNextByte;
        }

        return i1;
    }

    // Move pointer backwards by given amount of bits
    private void updatePointer(int bitsToMoveBack) {
        int i = bitPointer - bitsToMoveBack;

        if (i < 0) {
            bytePointer--;
            bitPointer = 8 + i;
        } else {
            bitPointer = i;
        }
    }

    // Move to the next byte boundary
    private boolean advancePointer() {
        if (bitPointer != 0) {
            bytePointer++;
            bitPointer = 0;
        }

        return true;
    }
}