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| @@ -0,0 +1,253 @@ | ||
| #region license | ||
| // Razor: An Ultima Online Assistant | ||
| // Copyright (c) 2024 Razor Development Community on GitHub <https://github.com/markdwags/Razor> | ||
| // | ||
| // This program is free software: you can redistribute it and/or modify | ||
| // it under the terms of the GNU General Public License as published by | ||
| // the Free Software Foundation, either version 3 of the License, or | ||
| // (at your option) any later version. | ||
| // | ||
| // This program is distributed in the hope that it will be useful, | ||
| // but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| // GNU General Public License for more details. | ||
| // | ||
| // You should have received a copy of the GNU General Public License | ||
| // along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
| #endregion | ||
| using System; | ||
| using System.IO; | ||
| using System.Linq; | ||
| using System.Runtime.InteropServices; | ||
|
|
||
| namespace Ultima | ||
| { | ||
| internal static class BwtDecompress | ||
| { | ||
| public static byte[] Decompress(byte[] buffer) | ||
| { | ||
| byte[] output = null; | ||
|
|
||
| using (var reader = new BinaryReader(new MemoryStream(buffer))) | ||
| { | ||
| var header = reader.ReadUInt32(); | ||
| var len = 0u; | ||
|
|
||
| var firstChar = reader.ReadByte(); | ||
|
|
||
| Span<ushort> table = new ushort[256 * 256]; | ||
| table = BuildTable(table, firstChar); | ||
|
|
||
| var list = new byte[reader.BaseStream.Length - 4]; | ||
| var i = 0; | ||
| while (reader.BaseStream.Position < reader.BaseStream.Length) | ||
| { | ||
| var currentValue = firstChar; | ||
| var value = table[currentValue]; | ||
| if (currentValue > 0) | ||
| { | ||
| do | ||
| { | ||
| table[currentValue] = table[currentValue - 1]; | ||
| } while (--currentValue > 0); | ||
| } | ||
|
|
||
| table[0] = value; | ||
|
|
||
| list[i++] = (byte) value; | ||
| firstChar = reader.ReadByte(); | ||
| } | ||
|
|
||
| output = InternalDecompress(list, len); | ||
| } | ||
|
|
||
| return output; | ||
| } | ||
|
|
||
| /// | ||
| static void MergeSort(Span<ushort> span) | ||
| { | ||
| if (span.Length <= 1) | ||
| return; | ||
|
|
||
| var list = span.ToArray().ToList(); | ||
| list.Sort(); | ||
|
|
||
| int mid = span.Length / 2; | ||
| var left = span.Slice(0, mid); | ||
| var right = span.Slice(mid); | ||
|
|
||
| MergeSort(left); | ||
| MergeSort(right); | ||
|
|
||
| Merge(span, left, right); | ||
| } | ||
|
|
||
| static void Merge(Span<ushort> destination, Span<ushort> left, Span<ushort> right) | ||
| { | ||
| int i = 0, j = 0, k = 0; | ||
|
|
||
| while (i < left.Length && j < right.Length) | ||
| { | ||
| if (left[i] <= right[j]) | ||
| { | ||
| destination[k++] = left[i++]; | ||
| } | ||
| else | ||
| { | ||
| destination[k++] = right[j++]; | ||
| } | ||
| } | ||
|
|
||
| while (i < left.Length) | ||
| { | ||
| destination[k++] = left[i++]; | ||
| } | ||
|
|
||
| while (j < right.Length) | ||
| { | ||
| destination[k++] = right[j++]; | ||
| } | ||
| } | ||
|
|
||
| /// | ||
|
|
||
| static Span<ushort> BuildTable(Span<ushort> table, byte startValue) | ||
| { | ||
| int index = 0; | ||
| byte firstByte = startValue; | ||
| byte secondByte = 0; | ||
| for (int i = 0; i < 256 * 256; i++) | ||
| { | ||
| var val = (ushort) (firstByte + (secondByte << 8)); | ||
| table[index++] = val; | ||
|
|
||
| firstByte++; | ||
| if (firstByte == 0) | ||
| { | ||
| secondByte++; | ||
| } | ||
| } | ||
|
|
||
| var list = table.ToArray().ToList(); | ||
| list.Sort(); | ||
| return list.ToArray(); | ||
| } | ||
|
|
||
| static byte[] InternalDecompress(Span<byte> input, uint len) | ||
| { | ||
| Span<char> symbolTable = stackalloc char[256]; | ||
| Span<char> frequency = stackalloc char[256]; | ||
| Span<int> partialInput = stackalloc int[256 * 3]; | ||
| partialInput.Clear(); | ||
|
|
||
| for (var i = 0; i < 256; i++) | ||
| symbolTable[i] = (char) i; | ||
|
|
||
| input.Slice(0, 1024).CopyTo(MemoryMarshal.AsBytes(partialInput)); | ||
|
|
||
| var sum = 0; | ||
| for (var i = 0; i < 256; i++) | ||
| sum += partialInput[i]; | ||
|
|
||
| if (len == 0) | ||
| { | ||
| len = (uint) sum; | ||
| } | ||
|
|
||
| if (sum != len) | ||
| return Array.Empty<byte>(); | ||
|
|
||
| var output = new byte[len]; | ||
|
|
||
| var count = 0; | ||
| var nonZeroCount = 0; | ||
|
|
||
| for (var i = 0; i < 256; i++) | ||
| { | ||
| if (partialInput[i] != 0) | ||
| nonZeroCount++; | ||
| } | ||
|
|
||
| Frequency(partialInput, frequency); | ||
|
|
||
| for (int i = 0, m = 0; i < nonZeroCount; ++i) | ||
| { | ||
| var freq = (byte) frequency[i]; | ||
| symbolTable[input[m + 1024]] = (char) freq; | ||
| partialInput[freq + 256] = m + 1; | ||
| m += partialInput[freq]; | ||
| partialInput[freq + 512] = m; | ||
| } | ||
|
|
||
| var val = (byte) symbolTable[0]; | ||
|
|
||
| if (len != 0) | ||
| { | ||
| do | ||
| { | ||
| ref var firstValRef = ref partialInput[val + 256]; | ||
| output[count] = val; | ||
|
|
||
| if (firstValRef >= partialInput[val + 512]) | ||
| { | ||
| if (nonZeroCount-- > 0) | ||
| { | ||
| ShiftLeft(symbolTable, nonZeroCount); | ||
| val = (byte) symbolTable[0]; | ||
| } | ||
| } | ||
| else | ||
| { | ||
| var idx = (char) input[firstValRef + 1024]; | ||
| firstValRef++; | ||
|
|
||
| if (idx != 0) | ||
| { | ||
| ShiftLeft(symbolTable, idx); | ||
| symbolTable[(byte) idx] = (char) val; | ||
| val = (byte) symbolTable[0]; | ||
| } | ||
| } | ||
|
|
||
| count++; | ||
| } while (count < len); | ||
| } | ||
|
|
||
| return output; | ||
| } | ||
|
|
||
| static void Frequency(Span<int> input, Span<char> output) | ||
| { | ||
| Span<int> tmp = stackalloc int[256]; | ||
| input.Slice(0, tmp.Length).CopyTo(tmp); | ||
|
|
||
| for (var i = 0; i < 256; i++) | ||
| { | ||
| uint value = 0; | ||
| byte index = 0; | ||
|
|
||
| for (var j = 0; j < 256; j++) | ||
| { | ||
| if (tmp[j] > value) | ||
| { | ||
| index = (byte) j; | ||
| value = (uint) tmp[j]; | ||
| } | ||
| } | ||
|
|
||
| if (value == 0) | ||
| break; | ||
|
|
||
| output[i] = (char) index; | ||
| tmp[index] = 0; | ||
| } | ||
| } | ||
|
|
||
| static void ShiftLeft(Span<char> input, int max) | ||
| { | ||
| for (var i = 0; i < max; ++i) | ||
| input[i] = input[i + 1]; | ||
| } | ||
| } | ||
| } |
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