dsdecmp/CSharp/DSDecmp/Formats/Nitro/RLE.cs

124 lines
5.0 KiB
C#

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
namespace DSDecmp.Formats.Nitro
{
public class RLE : NitroCFormat
{
public RLE() : base(0x30) { }
public override void Decompress(Stream instream, long inLength, Stream outstream)
{
/*
Data header (32bit)
Bit 0-3 Reserved
Bit 4-7 Compressed type (must be 3 for run-length)
Bit 8-31 Size of decompressed data
Repeat below. Each Flag Byte followed by one or more Data Bytes.
Flag data (8bit)
Bit 0-6 Expanded Data Length (uncompressed N-1, compressed N-3)
Bit 7 Flag (0=uncompressed, 1=compressed)
Data Byte(s) - N uncompressed bytes, or 1 byte repeated N times
*/
long readBytes = 0;
byte type = (byte)instream.ReadByte();
if (type != base.magicByte)
throw new InvalidDataException("The provided stream is not a valid LZ-0x11 "
+ "compressed stream (invalid type 0x" + type.ToString("X") + ")");
byte[] sizeBytes = new byte[3];
instream.Read(sizeBytes, 0, 3);
int decompressedSize = base.Bytes2Size(sizeBytes);
readBytes += 4;
if (decompressedSize == 0)
{
sizeBytes = new byte[4];
instream.Read(sizeBytes, 0, 4);
decompressedSize = base.Bytes2Size(sizeBytes);
readBytes += 4;
}
int currentOutSize = 0;
while (currentOutSize < decompressedSize)
{
#region (try to) get the flag byte with the length data and compressed flag
if (readBytes >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
int flag = instream.ReadByte(); readBytes++;
if (flag < 0)
throw new StreamTooShortException();
bool compressed = (flag & 0x80) > 0;
int length = flag & 0x7F;
if (compressed)
length += 3;
else
length += 1;
#endregion
if (compressed)
{
#region compressed: write the next byte (length) times.
if (readBytes >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
int data = instream.ReadByte(); readBytes++;
if (data < 0)
throw new StreamTooShortException();
if (currentOutSize + length > decompressedSize)
throw new InvalidDataException("The given stream is not a valid RLE stream; the "
+ "output length does not match the provided plaintext length.");
byte bdata = (byte)data;
for (int i = 0; i < length; i++)
{
// Stream.Write(byte[], offset, len) may also work, but only if it is a circular buffer
outstream.WriteByte(bdata);
currentOutSize++;
}
#endregion
}
else
{
#region uncompressed: copy the next (length) bytes.
int tryReadLength = length;
// limit the amount of bytes read by the indicated number of bytes available
if (readBytes + length > inLength)
tryReadLength = (int)(inLength - readBytes);
byte[] data = new byte[length];
int readLength = instream.Read(data, 0, (int)tryReadLength);
readBytes += readLength;
outstream.Write(data, 0, readLength);
currentOutSize += readLength;
// if the attempted number of bytes read is less than the desired number, the given input
// length is too small (or there is not enough data in the stream)
if (tryReadLength < length)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
// if the actual number of read bytes is even less, it means that the end of the stream has
// bee reached, thus the given input length is larger than the actual length of the input
if (readLength < length)
throw new StreamTooShortException();
#endregion
}
}
}
public override void Compress(Stream instream, long inLength, Stream outstream)
{
throw new NotImplementedException();
}
}
}