117 lines
3.8 KiB
C#
117 lines
3.8 KiB
C#
using LibXom.Exceptions;
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Threading.Tasks;
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namespace LibXom.Data
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{
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public class XomCompressor
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{
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internal static int readCompressedIntFromStream(MemoryStream ms)
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{
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byte[] buffer = new byte[4];
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for (int i = 0; i < 4; i++)
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{
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int b = ms.ReadByte();
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buffer[i] = Convert.ToByte(b);
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if (b > 0x7F) continue;
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else break;
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}
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return DecompressInt(BitConverter.ToInt32(buffer));
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}
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internal static int[] decompressBuffer(byte[] input)
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{
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List<int> decompressedData = new List<int>();
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using (MemoryStream inputStream = new MemoryStream(input))
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{
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while (inputStream.Position < inputStream.Length)
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{
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int n = readCompressedIntFromStream(inputStream);
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decompressedData.Add(n);
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}
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}
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return decompressedData.ToArray();
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}
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private static int getNumberByteCount(int num)
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{
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uint unum = Convert.ToUInt32(num);
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if (unum <= 0xFF) return 1;
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if (unum <= 0xFFFF) return 2;
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if (unum <= 0xFFFFFF) return 3;
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if (unum <= 0xFFFFFFFF) return 4;
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throw new XomException("Number is too large or too small.");
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}
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private static int pow(int val, int pow)
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{
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return Convert.ToInt32(Math.Pow(val, pow));
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}
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// TODO: Write the inverse of this; "CompressInt()"
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public static int DecompressInt(int compressedInt)
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{
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int b1 = (compressedInt & 0xFF);
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int b2 = (compressedInt >> 8) & 0xFF;
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int b3 = (compressedInt >> 16) & 0xFF;
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int b4 = (compressedInt >> 24) & 0xFF;
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return (b4 * pow(0x80, 3)) + ((b3 % 0x80) * pow(0x80, 0x2)) + ((b2 % 0x80) * pow(0x80, 1)) + (b1 % 0x80);
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}
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public static int NextCompressedInterger(int compressedInt)
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{
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// Some parts of XOM follow a particular pattern,
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// 0x7b, 0x7d, 0x7e, 0x7f, 0x180
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// 0x1fb, 0x1fd, 0x1fe, 0x1ff 0x280
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// 0x2fb, 0x2fd, 0x2fe, 0x2ff 0x380
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// This function will take any given int,
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// and give you the next following this sequence.
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// This is done by XOM to "compress" intergers,
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// you can read a int and, if its > 0x7f you know theres another byte to be read
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// otherwise you've read the entire interger, and can read the next one
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// add 1 to current int
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int nextId = compressedInt + 1;
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int byteCount = getNumberByteCount(nextId);
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// if its 0, just return 0
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if (nextId <= 0) return nextId;
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// if its a multiple of 0x80..
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if (nextId % 0x8000 == 0)
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{
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int div = nextId / 0x8000;
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// check if that divisor is also divisible by 2
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if (div % 0x2 == 0)
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nextId += (0x8000); // add 0x8000
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}
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if (nextId % 0x80 == 0)
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{
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int div = nextId / 0x80;
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// check if that divisor is also divisible by 2
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if (div % 0x2 == 0)
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nextId += (0x80); // add 0x80
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}
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byte[] buffer = BitConverter.GetBytes(nextId);
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for(int i = 0; i < 4; i++)
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{
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if (buffer[i] > 0x7F) continue;
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if (buffer[i] == 0) buffer[i]++;
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break;
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}
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nextId = BitConverter.ToInt32(buffer);
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return nextId;
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}
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}
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}
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