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3a6221a0c6
The current RLE implementation passed the first test: compression->decompression resulted in the same file for a manually created test file. (and the compressed file also has the expected format)
252 lines
10 KiB
C#
252 lines
10 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Text;
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using System.IO;
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namespace DSDecmp.Formats.Nitro
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{
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/// <summary>
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/// Compressor and decompressor for the RLE format used in several of the games for the
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/// newer Nintendo consoles and handhelds.
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/// </summary>
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public class RLE : NitroCFormat
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{
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public RLE() : base(0x30) { }
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public override void Decompress(Stream instream, long inLength, Stream outstream)
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{
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/*
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Data header (32bit)
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Bit 0-3 Reserved
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Bit 4-7 Compressed type (must be 3 for run-length)
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Bit 8-31 Size of decompressed data
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Repeat below. Each Flag Byte followed by one or more Data Bytes.
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Flag data (8bit)
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Bit 0-6 Expanded Data Length (uncompressed N-1, compressed N-3)
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Bit 7 Flag (0=uncompressed, 1=compressed)
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Data Byte(s) - N uncompressed bytes, or 1 byte repeated N times
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*/
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long readBytes = 0;
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byte type = (byte)instream.ReadByte();
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if (type != base.magicByte)
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throw new InvalidDataException("The provided stream is not a valid LZ-0x11 "
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+ "compressed stream (invalid type 0x" + type.ToString("X") + ")");
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byte[] sizeBytes = new byte[3];
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instream.Read(sizeBytes, 0, 3);
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int decompressedSize = base.Bytes2Size(sizeBytes);
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readBytes += 4;
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if (decompressedSize == 0)
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{
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sizeBytes = new byte[4];
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instream.Read(sizeBytes, 0, 4);
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decompressedSize = base.Bytes2Size(sizeBytes);
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readBytes += 4;
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}
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int currentOutSize = 0;
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while (currentOutSize < decompressedSize)
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{
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#region (try to) get the flag byte with the length data and compressed flag
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if (readBytes >= inLength)
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throw new NotEnoughDataException(currentOutSize, decompressedSize);
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int flag = instream.ReadByte(); readBytes++;
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if (flag < 0)
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throw new StreamTooShortException();
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bool compressed = (flag & 0x80) > 0;
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int length = flag & 0x7F;
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if (compressed)
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length += 3;
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else
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length += 1;
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#endregion
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if (compressed)
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{
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#region compressed: write the next byte (length) times.
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if (readBytes >= inLength)
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throw new NotEnoughDataException(currentOutSize, decompressedSize);
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int data = instream.ReadByte(); readBytes++;
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if (data < 0)
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throw new StreamTooShortException();
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if (currentOutSize + length > decompressedSize)
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throw new InvalidDataException("The given stream is not a valid RLE stream; the "
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+ "output length does not match the provided plaintext length.");
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byte bdata = (byte)data;
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for (int i = 0; i < length; i++)
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{
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// Stream.Write(byte[], offset, len) may also work, but only if it is a circular buffer
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outstream.WriteByte(bdata);
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currentOutSize++;
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}
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#endregion
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}
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else
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{
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#region uncompressed: copy the next (length) bytes.
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int tryReadLength = length;
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// limit the amount of bytes read by the indicated number of bytes available
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if (readBytes + length > inLength)
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tryReadLength = (int)(inLength - readBytes);
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byte[] data = new byte[length];
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int readLength = instream.Read(data, 0, (int)tryReadLength);
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readBytes += readLength;
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outstream.Write(data, 0, readLength);
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currentOutSize += readLength;
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// if the attempted number of bytes read is less than the desired number, the given input
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// length is too small (or there is not enough data in the stream)
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if (tryReadLength < length)
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throw new NotEnoughDataException(currentOutSize, decompressedSize);
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// if the actual number of read bytes is even less, it means that the end of the stream has
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// bee reached, thus the given input length is larger than the actual length of the input
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if (readLength < length)
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throw new StreamTooShortException();
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#endregion
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}
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}
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if (readBytes < inLength)
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throw new TooMuchInputException(readBytes, inLength);
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}
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public override int Compress(Stream instream, long inLength, Stream outstream)
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{
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if (inLength > 0xFFFFFF)
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throw new InputTooLargeException();
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List<byte> compressedData = new List<byte>();
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// at most 0x7F+3=130 bytes are compressed into a single block.
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// (and at most 0x7F+1=128 in an uncompressed block, however we need to read 2
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// more, since the last byte may be part of a repetition).
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byte[] dataBlock = new byte[130];
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// the length of the valid content in the current data block
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int currentBlockLength = 0;
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int readLength = 0;
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int nextByte;
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int repCount = 1;
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while (readLength < inLength)
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{
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bool foundRepetition = false;
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while (currentBlockLength < dataBlock.Length && readLength < inLength)
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{
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nextByte = instream.ReadByte();
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if (nextByte < 0)
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throw new StreamTooShortException();
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readLength++;
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dataBlock[currentBlockLength++] = (byte)nextByte;
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if (currentBlockLength > 1)
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{
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if (nextByte == dataBlock[currentBlockLength - 2])
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repCount++;
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else
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repCount = 1;
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}
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foundRepetition = repCount > 2;
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if (foundRepetition)
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break;
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}
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int numUncompToCopy = 0;
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if (foundRepetition)
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{
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// if a repetition was found, copy block size - 3 bytes as compressed data
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numUncompToCopy = currentBlockLength - 3;
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}
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else
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{
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// if no repetition was found, copy min(block size, max block size - 2) bytes as uncompressed data.
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numUncompToCopy = Math.Min(currentBlockLength, dataBlock.Length - 2);
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}
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#region insert uncompressed block
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if (numUncompToCopy > 0)
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{
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byte flag = (byte)(numUncompToCopy - 1);
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compressedData.Add(flag);
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for (int i = 0; i < numUncompToCopy; i++)
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compressedData.Add(dataBlock[i]);
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// shift some possibly remaining bytes to the start
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for (int i = numUncompToCopy; i < currentBlockLength; i++)
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dataBlock[i - numUncompToCopy] = dataBlock[i];
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currentBlockLength -= numUncompToCopy;
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}
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#endregion
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if (foundRepetition)
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{
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// if a repetition was found, continue until the first different byte
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// (or until the buffer is full)
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while (currentBlockLength < dataBlock.Length && readLength < inLength)
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{
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nextByte = instream.ReadByte();
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if (nextByte < 0)
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throw new StreamTooShortException();
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readLength++;
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dataBlock[currentBlockLength++] = (byte)nextByte;
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if (nextByte != dataBlock[0])
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break;
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else
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repCount++;
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}
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// the next repCount bytes are the same.
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#region insert compressed block
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byte flag = (byte)(0x80 | (repCount - 3));
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compressedData.Add(flag);
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compressedData.Add(dataBlock[0]);
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// make sure to shift the possible extra byte to the start
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if (repCount != currentBlockLength)
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dataBlock[0] = dataBlock[currentBlockLength - 1];
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currentBlockLength -= repCount;
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#endregion
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}
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}
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// write any reamaining bytes as uncompressed
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if (currentBlockLength > 0)
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{
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byte flag = (byte)(currentBlockLength - 1);
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compressedData.Add(flag);
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for (int i = 0; i < currentBlockLength; i++)
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compressedData.Add(dataBlock[i]);
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currentBlockLength = 0;
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}
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// write the RLE marker and the decompressed size
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outstream.WriteByte(0x30);
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int compLen = compressedData.Count;
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outstream.WriteByte((byte)(inLength & 0xFF));
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outstream.WriteByte((byte)((inLength >> 8) & 0xFF));
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outstream.WriteByte((byte)((inLength >> 16) & 0xFF));
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// write the compressed data
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outstream.Write(compressedData.ToArray(), 0, compLen);
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// the total compressed stream length is the compressed data length + the 4-byte header
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return compLen + 4;
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}
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}
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}
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