mirror of
https://github.com/GreemDev/Ryujinx.git
synced 2024-12-25 12:35:47 +00:00
105 lines
2.9 KiB
C#
105 lines
2.9 KiB
C#
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using System;
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using System.IO;
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namespace Ryujinx.HLE.Loaders.Compression
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{
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static class BackwardsLz
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{
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private class BackwardsReader
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{
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private Stream BaseStream;
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public BackwardsReader(Stream BaseStream)
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{
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this.BaseStream = BaseStream;
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}
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public byte ReadByte()
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{
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BaseStream.Seek(-1, SeekOrigin.Current);
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byte Value = (byte)BaseStream.ReadByte();
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BaseStream.Seek(-1, SeekOrigin.Current);
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return Value;
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}
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public short ReadInt16()
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{
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return (short)((ReadByte() << 8) | (ReadByte() << 0));
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}
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public int ReadInt32()
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{
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return ((ReadByte() << 24) |
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(ReadByte() << 16) |
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(ReadByte() << 8) |
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(ReadByte() << 0));
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}
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}
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public static byte[] Decompress(Stream Input, int DecompressedLength)
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{
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long End = Input.Position;
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BackwardsReader Reader = new BackwardsReader(Input);
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int AdditionalDecLength = Reader.ReadInt32();
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int StartOffset = Reader.ReadInt32();
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int CompressedLength = Reader.ReadInt32();
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Input.Seek(12 - StartOffset, SeekOrigin.Current);
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byte[] Dec = new byte[DecompressedLength];
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int DecompressedLengthUnpadded = CompressedLength + AdditionalDecLength;
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int DecompressionStart = DecompressedLength - DecompressedLengthUnpadded;
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int DecPos = Dec.Length;
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byte Mask = 0;
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byte Header = 0;
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while (DecPos > DecompressionStart)
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{
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if ((Mask >>= 1) == 0)
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{
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Header = Reader.ReadByte();
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Mask = 0x80;
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}
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if ((Header & Mask) == 0)
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{
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Dec[--DecPos] = Reader.ReadByte();
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}
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else
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{
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ushort Pair = (ushort)Reader.ReadInt16();
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int Length = (Pair >> 12) + 3;
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int Position = (Pair & 0xfff) + 3;
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DecPos -= Length;
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if (Length <= Position)
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{
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int SrcPos = DecPos + Position;
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Buffer.BlockCopy(Dec, SrcPos, Dec, DecPos, Length);
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}
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else
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{
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for (int Offset = 0; Offset < Length; Offset++)
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{
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Dec[DecPos + Offset] = Dec[DecPos + Position + Offset];
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}
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}
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}
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}
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return Dec;
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}
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}
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}
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