LibHac/libhac.Nand/DiscUtils.Core/Compression/BZip2Randomizer.cs

//
// Copyright (c) 2008-2011, Kenneth Bell
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//

//
// Based on "libbzip2", Copyright (C) 1996-2007 Julian R Seward.
//

using System;

namespace DiscUtils.Compression
{
    internal class BZip2Randomizer : DataBlockTransform
    {
        private static readonly int[] RandomVals =
        {
            619, 720, 127, 481, 931, 816, 813, 233, 566, 247,
            985, 724, 205, 454, 863, 491, 741, 242, 949, 214,
            733, 859, 335, 708, 621, 574, 73, 654, 730, 472,
            419, 436, 278, 496, 867, 210, 399, 680, 480, 51,
            878, 465, 811, 169, 869, 675, 611, 697, 867, 561,
            862, 687, 507, 283, 482, 129, 807, 591, 733, 623,
            150, 238, 59, 379, 684, 877, 625, 169, 643, 105,
            170, 607, 520, 932, 727, 476, 693, 425, 174, 647,
            73, 122, 335, 530, 442, 853, 695, 249, 445, 515,
            909, 545, 703, 919, 874, 474, 882, 500, 594, 612,
            641, 801, 220, 162, 819, 984, 589, 513, 495, 799,
            161, 604, 958, 533, 221, 400, 386, 867, 600, 782,
            382, 596, 414, 171, 516, 375, 682, 485, 911, 276,
            98, 553, 163, 354, 666, 933, 424, 341, 533, 870,
            227, 730, 475, 186, 263, 647, 537, 686, 600, 224,
            469, 68, 770, 919, 190, 373, 294, 822, 808, 206,
            184, 943, 795, 384, 383, 461, 404, 758, 839, 887,
            715, 67, 618, 276, 204, 918, 873, 777, 604, 560,
            951, 160, 578, 722, 79, 804, 96, 409, 713, 940,
            652, 934, 970, 447, 318, 353, 859, 672, 112, 785,
            645, 863, 803, 350, 139, 93, 354, 99, 820, 908,
            609, 772, 154, 274, 580, 184, 79, 626, 630, 742,
            653, 282, 762, 623, 680, 81, 927, 626, 789, 125,
            411, 521, 938, 300, 821, 78, 343, 175, 128, 250,
            170, 774, 972, 275, 999, 639, 495, 78, 352, 126,
            857, 956, 358, 619, 580, 124, 737, 594, 701, 612,
            669, 112, 134, 694, 363, 992, 809, 743, 168, 974,
            944, 375, 748, 52, 600, 747, 642, 182, 862, 81,
            344, 805, 988, 739, 511, 655, 814, 334, 249, 515,
            897, 955, 664, 981, 649, 113, 974, 459, 893, 228,
            433, 837, 553, 268, 926, 240, 102, 654, 459, 51,
            686, 754, 806, 760, 493, 403, 415, 394, 687, 700,
            946, 670, 656, 610, 738, 392, 760, 799, 887, 653,
            978, 321, 576, 617, 626, 502, 894, 679, 243, 440,
            680, 879, 194, 572, 640, 724, 926, 56, 204, 700,
            707, 151, 457, 449, 797, 195, 791, 558, 945, 679,
            297, 59, 87, 824, 713, 663, 412, 693, 342, 606,
            134, 108, 571, 364, 631, 212, 174, 643, 304, 329,
            343, 97, 430, 751, 497, 314, 983, 374, 822, 928,
            140, 206, 73, 263, 980, 736, 876, 478, 430, 305,
            170, 514, 364, 692, 829, 82, 855, 953, 676, 246,
            369, 970, 294, 750, 807, 827, 150, 790, 288, 923,
            804, 378, 215, 828, 592, 281, 565, 555, 710, 82,
            896, 831, 547, 261, 524, 462, 293, 465, 502, 56,
            661, 821, 976, 991, 658, 869, 905, 758, 745, 193,
            768, 550, 608, 933, 378, 286, 215, 979, 792, 961,
            61, 688, 793, 644, 986, 403, 106, 366, 905, 644,
            372, 567, 466, 434, 645, 210, 389, 550, 919, 135,
            780, 773, 635, 389, 707, 100, 626, 958, 165, 504,
            920, 176, 193, 713, 857, 265, 203, 50, 668, 108,
            645, 990, 626, 197, 510, 357, 358, 850, 858, 364,
            936, 638
        };

        protected override bool BuffersMustNotOverlap
        {
            get { return false; }
        }

        protected override int DoProcess(byte[] input, int inputOffset, int inputCount, byte[] output, int outputOffset)
        {
            if (input != output || inputOffset != outputOffset)
            {
                Array.Copy(input, inputOffset, output, outputOffset, inputCount);
            }

            int randIndex = 1;
            int nextByte = RandomVals[0] - 2;

            while (nextByte < inputCount)
            {
                output[nextByte] ^= 1;
                nextByte += RandomVals[randIndex++];
                randIndex &= 0x1FF;
            }

            return inputCount;
        }

        protected override int MaxOutputCount(int inputCount)
        {
            return inputCount;
        }

        protected override int MinOutputCount(int inputCount)
        {
            return inputCount;
        }
    }
}