91 lines
3.1 KiB
C#
91 lines
3.1 KiB
C#
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 UniversalEditor.Accessors;
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using UniversalEditor.IO;
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namespace UniversalEditor.Compression.Modules.LZRW1
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{
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public class LZRW1CompressionModule : CompressionModule
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{
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/// <summary>
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/// Number of bytes used by copy flag
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/// </summary>
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private const byte FLAG_BYTES = 0x04;
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private const byte FLAG_COMPRESS = 0x00;
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private const byte FLAG_COPY = 0x01;
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public override string Name
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{
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get { return "LZRW1"; }
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}
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protected override void CompressInternal(System.IO.Stream inputStream, System.IO.Stream outputStream)
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{
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throw new NotImplementedException();
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}
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protected override void DecompressInternal(System.IO.Stream inputStream, System.IO.Stream outputStream, int inputLength, int outputLength)
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{
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StreamAccessor sao = new StreamAccessor(outputStream);
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StreamAccessor sai = new StreamAccessor(inputStream);
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Reader br = new Reader(sai);
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Writer bw = new Writer(sao);
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int flag = br.ReadInt32();
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if (flag == FLAG_COPY)
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{
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// entire stream is uncompressed, so read it all
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byte[] data = br.ReadToEnd();
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bw.WriteBytes(data);
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}
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else
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{
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// flag is not copy, so we have to decompress
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ushort controlbits = 0, control = 0;
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while (!br.EndOfStream)
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{
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if (controlbits == 0)
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{
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// control bits are 0, so it's time to read a new control ushort
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// don't use ReadUInt16 here because we need to keep the bytes
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// for future use
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control = br.ReadByte();
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control |= (ushort)(br.ReadByte() << 8);
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controlbits = 16;
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}
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if ((control & 1) != 0)
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{
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ushort offset, len;
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offset = (ushort)((br.PeekByte() & 0xF0) << 4);
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len = (ushort)(1 + (br.ReadByte() & 0xF));
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offset += (ushort)(br.ReadByte() & 0xFF);
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bw.Flush();
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long oldpos = sao.Position;
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sao.Position = sao.Length - offset;
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byte[] nextdata = sao.Reader.ReadBytes(len);
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sao.Position = oldpos;
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bw.WriteBytes(nextdata);
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}
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else
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{
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// control bit is 0, so perform a simple copy of the next byte
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bw.WriteByte(br.ReadByte());
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}
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// pop the latest control bit off the control ushort
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control >>= 1;
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controlbits--;
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}
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}
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bw.Flush();
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}
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}
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}
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