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dsdecmp/CSharp/DSDecmp/Formats/Nitro/LZ10.cs

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18 KiB
C#
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using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using DSDecmp.Utils;
namespace DSDecmp.Formats.Nitro
{
/// <summary>
/// Compressor and decompressor for the LZ-0x10 format used in many of the games for the
/// newer Nintendo consoles and handhelds.
/// </summary>
public class LZ10 : NitroCFormat
{
private static bool lookAhead = false;
/// <summary>
/// Sets the flag that determines if 'look-ahead'/DP should be used when compressing
/// with the LZ-10 format. The default is false, which is what is used in the original
/// implementation.
/// </summary>
public static bool LookAhead
{
set { lookAhead = value; }
}
public LZ10() : base(0x10) { }
#region 'Original' Decompression method
/// <summary>
/// Decompress a stream that is compressed in the LZ-10 format.
/// </summary>
/// <param name="instream">The compressed stream.</param>
/// <param name="inLength">The length of the input stream.</param>
/// <param name="outstream">The output stream, where the decompressed data is written to.</param>
public override long Decompress(Stream instream, long inLength,
Stream outstream)
{
#region format definition form GBATEK/NDSTEK
/* Data header (32bit)
Bit 0-3 Reserved
Bit 4-7 Compressed type (must be 1 for LZ77)
Bit 8-31 Size of decompressed data
Repeat below. Each Flag Byte followed by eight Blocks.
Flag data (8bit)
Bit 0-7 Type Flags for next 8 Blocks, MSB first
Block Type 0 - Uncompressed - Copy 1 Byte from Source to Dest
Bit 0-7 One data byte to be copied to dest
Block Type 1 - Compressed - Copy N+3 Bytes from Dest-Disp-1 to Dest
Bit 0-3 Disp MSBs
Bit 4-7 Number of bytes to copy (minus 3)
Bit 8-15 Disp LSBs
*/
#endregion
long readBytes = 0;
byte type = (byte)instream.ReadByte();
if (type != base.magicByte)
throw new InvalidDataException("The provided stream is not a valid LZ-0x10 "
+ "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;
}
// the maximum 'DISP-1' is 0xFFF.
int bufferLength = 0x1000;
byte[] buffer = new byte[bufferLength];
int bufferOffset = 0;
int currentOutSize = 0;
int flags = 0, mask = 1;
while (currentOutSize < decompressedSize)
{
// (throws when requested new flags byte is not available)
#region Update the mask. If all flag bits have been read, get a new set.
// the current mask is the mask used in the previous run. So if it masks the
// last flag bit, get a new flags byte.
if (mask == 1)
{
if (readBytes >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
flags = instream.ReadByte(); readBytes++;
if (flags < 0)
throw new StreamTooShortException();
mask = 0x80;
}
else
{
mask >>= 1;
}
#endregion
// bit = 1 <=> compressed.
if ((flags & mask) > 0)
{
// (throws when < 2 bytes are available)
#region Get length and displacement('disp') values from next 2 bytes
// there are < 2 bytes available when the end is at most 1 byte away
if (readBytes + 1 >= inLength)
{
// make sure the stream is at the end
if (readBytes < inLength)
{
instream.ReadByte(); readBytes++;
}
throw new NotEnoughDataException(currentOutSize, decompressedSize);
}
int byte1 = instream.ReadByte(); readBytes++;
int byte2 = instream.ReadByte(); readBytes++;
if (byte2 < 0)
throw new StreamTooShortException();
// the number of bytes to copy
int length = byte1 >> 4;
length += 3;
// from where the bytes should be copied (relatively)
int disp = ((byte1 & 0x0F) << 8) | byte2;
disp += 1;
if (disp > currentOutSize)
throw new InvalidDataException("Cannot go back more than already written. "
+ "DISP = 0x" + disp.ToString("X") + ", #written bytes = 0x" + currentOutSize.ToString("X")
+ " at 0x" + instream.Position.ToString("X"));
#endregion
int bufIdx = bufferOffset + bufferLength - disp;
for (int i = 0; i < length; i++)
{
byte next = buffer[bufIdx % bufferLength];
bufIdx++;
outstream.WriteByte(next);
buffer[bufferOffset] = next;
bufferOffset = (bufferOffset + 1) % bufferLength;
}
currentOutSize += length;
}
else
{
if (readBytes >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
int next = instream.ReadByte(); readBytes++;
if (next < 0)
throw new StreamTooShortException();
currentOutSize++;
outstream.WriteByte((byte)next);
buffer[bufferOffset] = (byte)next;
bufferOffset = (bufferOffset + 1) % bufferLength;
}
outstream.Flush();
}
if (readBytes < inLength)
{
// the input may be 4-byte aligned.
if ((readBytes ^ (readBytes & 3)) + 4 < inLength)
throw new TooMuchInputException(readBytes, inLength);
}
return decompressedSize;
}
#endregion
#region Original Compress method
public unsafe override int Compress(Stream instream, long inLength, Stream outstream)
{
// make sure the decompressed size fits in 3 bytes.
// There should be room for four bytes, however I'm not 100% sure if that can be used
// in every game, as it may not be a built-in function.
if (inLength > 0xFFFFFF)
throw new InputTooLargeException();
// use the other method if lookahead is enabled
if (lookAhead)
{
return CompressWithLA(instream, inLength, outstream);
}
// save the input data in an array to prevent having to go back and forth in a file
byte[] indata = new byte[inLength];
int numReadBytes = instream.Read(indata, 0, (int)inLength);
if (numReadBytes != inLength)
throw new StreamTooShortException();
// write the compression header first
outstream.WriteByte(this.magicByte);
outstream.WriteByte((byte)(inLength & 0xFF));
outstream.WriteByte((byte)((inLength >> 8) & 0xFF));
outstream.WriteByte((byte)((inLength >> 16) & 0xFF));
int compressedLength = 4;
fixed (byte* instart = &indata[0])
{
// we do need to buffer the output, as the first byte indicates which blocks are compressed.
// this version does not use a look-ahead, so we do not need to buffer more than 8 blocks at a time.
byte[] outbuffer = new byte[8 * 2 + 1];
outbuffer[0] = 0;
int bufferlength = 1, bufferedBlocks = 0;
int readBytes = 0;
while (readBytes < inLength)
{
#region If 8 blocks are bufferd, write them and reset the buffer
// we can only buffer 8 blocks at a time.
if (bufferedBlocks == 8)
{
outstream.Write(outbuffer, 0, bufferlength);
compressedLength += bufferlength;
// reset the buffer
outbuffer[0] = 0;
bufferlength = 1;
bufferedBlocks = 0;
}
#endregion
// determine if we're dealing with a compressed or raw block.
// it is a compressed block when the next 3 or more bytes can be copied from
// somewhere in the set of already compressed bytes.
int disp;
int oldLength = Math.Min(readBytes, 0x1000);
int length = LZUtil.GetOccurrenceLength(instart + readBytes, (int)Math.Min(inLength - readBytes, 0x12),
instart + readBytes - oldLength, oldLength, out disp);
// length not 3 or more? next byte is raw data
if (length < 3)
{
outbuffer[bufferlength++] = *(instart + (readBytes++));
}
else
{
// 3 or more bytes can be copied? next (length) bytes will be compressed into 2 bytes
readBytes += length;
// mark the next block as compressed
outbuffer[0] |= (byte)(1 << (7 - bufferedBlocks));
outbuffer[bufferlength] = (byte)(((length - 3) << 4) & 0xF0);
outbuffer[bufferlength] |= (byte)(((disp - 1) >> 8) & 0x0F);
bufferlength++;
outbuffer[bufferlength] = (byte)((disp - 1) & 0xFF);
bufferlength++;
}
bufferedBlocks++;
}
// copy the remaining blocks to the output
if (bufferedBlocks > 0)
{
outstream.Write(outbuffer, 0, bufferlength);
compressedLength += bufferlength;
/*/ make the compressed file 4-byte aligned.
while ((compressedLength % 4) != 0)
{
outstream.WriteByte(0);
compressedLength++;
}/**/
}
}
return compressedLength;
}
#endregion
#region Dynamic Programming compression method
/// <summary>
/// Variation of the original compression method, making use of Dynamic Programming to 'look ahead'
/// and determine the optimal 'length' values for the compressed blocks. Is not 100% optimal,
/// as the flag-bytes are not taken into account.
/// </summary>
private unsafe int CompressWithLA(Stream instream, long inLength, Stream outstream)
{
// save the input data in an array to prevent having to go back and forth in a file
byte[] indata = new byte[inLength];
int numReadBytes = instream.Read(indata, 0, (int)inLength);
if (numReadBytes != inLength)
throw new StreamTooShortException();
// write the compression header first
outstream.WriteByte(this.magicByte);
outstream.WriteByte((byte)(inLength & 0xFF));
outstream.WriteByte((byte)((inLength >> 8) & 0xFF));
outstream.WriteByte((byte)((inLength >> 16) & 0xFF));
int compressedLength = 4;
fixed (byte* instart = &indata[0])
{
// we do need to buffer the output, as the first byte indicates which blocks are compressed.
// this version does not use a look-ahead, so we do not need to buffer more than 8 blocks at a time.
byte[] outbuffer = new byte[8 * 2 + 1];
outbuffer[0] = 0;
int bufferlength = 1, bufferedBlocks = 0;
int readBytes = 0;
// get the optimal choices for len and disp
int[] lengths, disps;
this.GetOptimalCompressionLengths(instart, indata.Length, out lengths, out disps);
while (readBytes < inLength)
{
// we can only buffer 8 blocks at a time.
if (bufferedBlocks == 8)
{
outstream.Write(outbuffer, 0, bufferlength);
compressedLength += bufferlength;
// reset the buffer
outbuffer[0] = 0;
bufferlength = 1;
bufferedBlocks = 0;
}
if (lengths[readBytes] == 1)
{
outbuffer[bufferlength++] = *(instart + (readBytes++));
}
else
{
// mark the next block as compressed
outbuffer[0] |= (byte)(1 << (7 - bufferedBlocks));
outbuffer[bufferlength] = (byte)(((lengths[readBytes] - 3) << 4) & 0xF0);
outbuffer[bufferlength] |= (byte)(((disps[readBytes] - 1) >> 8) & 0x0F);
bufferlength++;
outbuffer[bufferlength] = (byte)((disps[readBytes] - 1) & 0xFF);
bufferlength++;
readBytes += lengths[readBytes];
}
bufferedBlocks++;
}
// copy the remaining blocks to the output
if (bufferedBlocks > 0)
{
outstream.Write(outbuffer, 0, bufferlength);
compressedLength += bufferlength;
/*/ make the compressed file 4-byte aligned.
while ((compressedLength % 4) != 0)
{
outstream.WriteByte(0);
compressedLength++;
}/**/
}
}
return compressedLength;
}
#endregion
#region DP compression helper method; GetOptimalCompressionLengths
/// <summary>
/// Gets the optimal compression lengths for each start of a compressed block using Dynamic Programming.
/// This takes O(n^2) time.
/// </summary>
/// <param name="indata">The data to compress.</param>
/// <param name="inLength">The length of the data to compress.</param>
/// <param name="lengths">The optimal 'length' of the compressed blocks. For each byte in the input data,
/// this value is the optimal 'length' value. If it is 1, the block should not be compressed.</param>
/// <param name="disps">The 'disp' values of the compressed blocks. May be 0, in which case the
/// corresponding length will never be anything other than 1.</param>
private unsafe void GetOptimalCompressionLengths(byte* indata, int inLength, out int[] lengths, out int[] disps)
{
lengths = new int[inLength];
disps = new int[inLength];
int[] minLengths = new int[inLength];
for (int i = inLength - 1; i >= 0; i--)
{
// first get the compression length when the next byte is not compressed
minLengths[i] = int.MaxValue;
lengths[i] = 1;
if (i + 1 >= inLength)
minLengths[i] = 1;
else
minLengths[i] = 1 + minLengths[i + 1];
// then the optimal compressed length
int oldLength = Math.Min(0x1000, i);
// get the appropriate disp while at it. Takes at most O(n) time if oldLength is considered O(n)
// be sure to bound the input length with 0x12, as that's the maximum length for LZ-10 compressed blocks.
int maxLen = LZUtil.GetOccurrenceLength(indata + i, Math.Min(inLength - i, 0x12),
indata + i - oldLength, oldLength, out disps[i]);
if (disps[i] > i)
throw new Exception("disp is too large");
for (int j = 3; j <= maxLen; j++)
{
int newCompLen;
if (i + j >= inLength)
newCompLen = 2;
else
newCompLen = 2 + minLengths[i + j];
if (newCompLen < minLengths[i])
{
lengths[i] = j;
minLengths[i] = newCompLen;
}
}
}
// we could optimize this further to also optimize it with regard to the flag-bytes, but that would require 8 times
// more space and time (one for each position in the block) for only a potentially tiny increase in compression ratio.
}
#endregion
}
}
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