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pk3DS/pk3DS.Core/CTR/LZSS.cs
Evan Dixon 7997f06dc5 Initial split to pk3DS and pk3DS.Core
2017-05-27 17:53:32 -05:00

773 lines
36 KiB
C#
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using System;
using System.IO;
namespace pk3DS.Core.CTR
{
// LZSS (de)compression, heavily taken from dsdecmp
public static class LZSS
{
public static long Decompress(string infile, string outfile)
{
// make sure the output directory exists
string outDirectory = Path.GetDirectoryName(outfile);
if (!Directory.Exists(outDirectory))
Directory.CreateDirectory(outDirectory);
// open the two given files, and delegate to the format-specific code.
using (FileStream inStream = new FileStream(infile, FileMode.Open),
outStream = new FileStream(outfile, FileMode.Create))
{
return Decompress(inStream, inStream.Length, outStream);
}
}
/// <summary>
/// Decompresses the given stream, writing the decompressed data to the given output stream.
/// Assumes <code>Supports(instream)</code> returns <code>true</code>.
/// After this call, the input stream will be positioned at the end of the compressed stream,
/// or at the initial position + <code>inLength</code>, whichever comes first.
/// </summary>
/// <param name="instream">The stream to decompress. At the end of this method, the position
/// of this stream is directly after the compressed data.</param>
/// <param name="inLength">The length of the input data. Not necessarily all of the
/// input data may be read (if there is padding, for example), however never more than
/// this number of bytes is read from the input stream.</param>
/// <param name="outstream">The stream to write the decompressed data to.</param>
/// <returns>The length of the output data.</returns>
/// <exception cref="NotEnoughDataException">When the given length of the input data
/// is not enough to properly decompress the input.</exception>
public static long Decompress(Stream instream, long inLength, Stream outstream)
{
#region Format definition in NDSTEK style
/* Data header (32bit)
Bit 0-3 Reserved
Bit 4-7 Compressed type (must be 1 for LZ77)
Bit 8-31 Size of decompressed data. if 0, the next 4 bytes are decompressed length
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 LEN Bytes from Dest-Disp-1 to Dest
If Reserved is 0: - Default
Bit 0-3 Disp MSBs
Bit 4-7 LEN - 3
Bit 8-15 Disp LSBs
If Reserved is 1: - Higher compression rates for files with (lots of) long repetitions
Bit 4-7 Indicator
If Indicator > 1:
Bit 0-3 Disp MSBs
Bit 4-7 LEN - 1 (same bits as Indicator)
Bit 8-15 Disp LSBs
If Indicator is 1: A(B CD E)(F GH)
Bit 0-3 (LEN - 0x111) MSBs
Bit 4-7 Indicator; unused
Bit 8-15 (LEN- 0x111) 'middle'-SBs
Bit 16-19 Disp MSBs
Bit 20-23 (LEN - 0x111) LSBs
Bit 24-31 Disp LSBs
If Indicator is 0:
Bit 0-3 (LEN - 0x11) MSBs
Bit 4-7 Indicator; unused
Bit 8-11 Disp MSBs
Bit 12-15 (LEN - 0x11) LSBs
Bit 16-23 Disp LSBs
*/
#endregion
long readBytes = 0;
byte type = (byte)instream.ReadByte();
if (type != 0x11)
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 = IOUtils.ToNDSu24(sizeBytes, 0);
readBytes += 4;
if (decompressedSize == 0)
{
sizeBytes = new byte[4];
instream.Read(sizeBytes, 0, 4);
decompressedSize = IOUtils.ToNDSs32(sizeBytes, 0);
readBytes += 4;
}
// the maximum 'DISP-1' is still 0xFFF.
const 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 not enough bytes are available)
#region Get length and displacement('disp') values from next 2, 3 or 4 bytes
// read the first byte first, which also signals the size of the compressed block
if (readBytes >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
int byte1 = instream.ReadByte(); readBytes++;
if (byte1 < 0)
throw new StreamTooShortException();
int length = byte1 >> 4;
int disp;
if (length == 0)
{
#region case 0; 0(B C)(D EF) + (0x11)(0x1) = (LEN)(DISP)
// case 0:
// data = AB CD EF (with A=0)
// LEN = ABC + 0x11 == BC + 0x11
// DISP = DEF + 1
// we need two more bytes available
if (readBytes + 1 >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
int byte2 = instream.ReadByte(); readBytes++;
int byte3 = instream.ReadByte(); readBytes++;
if (byte3 < 0)
throw new StreamTooShortException();
length = (((byte1 & 0x0F) << 4) | (byte2 >> 4)) + 0x11;
disp = (((byte2 & 0x0F) << 8) | byte3) + 0x1;
#endregion
}
else if (length == 1)
{
#region case 1: 1(B CD E)(F GH) + (0x111)(0x1) = (LEN)(DISP)
// case 1:
// data = AB CD EF GH (with A=1)
// LEN = BCDE + 0x111
// DISP = FGH + 1
// we need three more bytes available
if (readBytes + 2 >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
int byte2 = instream.ReadByte(); readBytes++;
int byte3 = instream.ReadByte(); readBytes++;
int byte4 = instream.ReadByte(); readBytes++;
if (byte4 < 0)
throw new StreamTooShortException();
length = (((byte1 & 0x0F) << 12) | (byte2 << 4) | (byte3 >> 4)) + 0x111;
disp = (((byte3 & 0x0F) << 8) | byte4) + 0x1;
#endregion
}
else
{
#region case > 1: (A)(B CD) + (0x1)(0x1) = (LEN)(DISP)
// case other:
// data = AB CD
// LEN = A + 1
// DISP = BCD + 1
// we need only one more byte available
if (readBytes >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedSize);
int byte2 = instream.ReadByte(); readBytes++;
if (byte2 < 0)
throw new StreamTooShortException();
length = ((byte1 & 0xF0) >> 4) + 0x1;
disp = (((byte1 & 0x0F) << 8) | byte2) + 0x1;
#endregion
}
if (disp > currentOutSize)
throw new InvalidDataException("Cannot go back more than already written. "
+ "DISP = " + disp + ", #written bytes = 0x" + currentOutSize.ToString("X")
+ " before 0x" + instream.Position.ToString("X") + " with indicator 0x"
+ (byte1 >> 4).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();
outstream.WriteByte((byte)next); currentOutSize++;
buffer[bufferOffset] = (byte)next;
bufferOffset = (bufferOffset + 1) % bufferLength;
}
}
if (readBytes < inLength)
{
// the input may be 4-byte aligned.
if ((readBytes ^ (readBytes & 3)) + 4 < inLength)
throw new TooMuchInputException(readBytes, inLength);
}
return decompressedSize;
}
public static int Compress(string infile, string outfile)
{
// make sure the output directory exists
string outDirectory = Path.GetDirectoryName(outfile);
if (!Directory.Exists(outDirectory))
Directory.CreateDirectory(outDirectory);
// open the proper Streams, and delegate to the format-specific code.
using (FileStream inStream = File.Open(infile, FileMode.Open),
outStream = File.Create(outfile))
{
if (inStream.Length == 0) // empty file 'compression' to lzss container
{
byte[] blank = {0x11, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
outStream.Write(blank, 0, blank.Length);
return blank.Length;
}
return Compress(inStream, inStream.Length, outStream, true);
}
}
#region Original compression method
/// <summary>
/// Compresses the input using the 'original', unoptimized compression algorithm.
/// This algorithm should yield files that are the same as those found in the games.
/// (delegates to the optimized method if LookAhead is set)
/// </summary>
internal static unsafe int Compress(Stream instream, long inLength, Stream outstream, bool original)
{
// 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 (!original)
{
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(0x11);
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.
// (a block is at most 4 bytes long)
byte[] outbuffer = new byte[8 * 4 + 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, 0x10110),
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));
if (length > 0x110)
{
// case 1: 1(B CD E)(F GH) + (0x111)(0x1) = (LEN)(DISP)
outbuffer[bufferlength] = 0x10;
outbuffer[bufferlength] |= (byte)(((length - 0x111) >> 12) & 0x0F);
bufferlength++;
outbuffer[bufferlength] = (byte)(((length - 0x111) >> 4) & 0xFF);
bufferlength++;
outbuffer[bufferlength] = (byte)(((length - 0x111) << 4) & 0xF0);
}
else if (length > 0x10)
{
// case 0; 0(B C)(D EF) + (0x11)(0x1) = (LEN)(DISP)
outbuffer[bufferlength] = 0x00;
outbuffer[bufferlength] |= (byte)(((length - 0x111) >> 4) & 0x0F);
bufferlength++;
outbuffer[bufferlength] = (byte)(((length - 0x111) << 4) & 0xF0);
}
else
{
// case > 1: (A)(B CD) + (0x1)(0x1) = (LEN)(DISP)
outbuffer[bufferlength] = (byte)(((length - 1) << 4) & 0xF0);
}
// the last 1.5 bytes are always the disp
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;
}
#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>
internal static 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(0x11);
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.
// blocks are at most 4 bytes long.
byte[] outbuffer = new byte[8 * 4 + 1];
outbuffer[0] = 0;
int bufferlength = 1, bufferedBlocks = 0;
int readBytes = 0;
// get the optimal choices for len and disp
int[] lengths, disps;
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));
if (lengths[readBytes] > 0x110)
{
// case 1: 1(B CD E)(F GH) + (0x111)(0x1) = (LEN)(DISP)
outbuffer[bufferlength] = 0x10;
outbuffer[bufferlength] |= (byte)(((lengths[readBytes] - 0x111) >> 12) & 0x0F);
bufferlength++;
outbuffer[bufferlength] = (byte)(((lengths[readBytes] - 0x111) >> 4) & 0xFF);
bufferlength++;
outbuffer[bufferlength] = (byte)(((lengths[readBytes] - 0x111) << 4) & 0xF0);
}
else if (lengths[readBytes] > 0x10)
{
// case 0; 0(B C)(D EF) + (0x11)(0x1) = (LEN)(DISP)
outbuffer[bufferlength] = 0x00;
outbuffer[bufferlength] |= (byte)(((lengths[readBytes] - 0x111) >> 4) & 0x0F);
bufferlength++;
outbuffer[bufferlength] = (byte)(((lengths[readBytes] - 0x111) << 4) & 0xF0);
}
else
{
// case > 1: (A)(B CD) + (0x1)(0x1) = (LEN)(DISP)
outbuffer[bufferlength] = (byte)(((lengths[readBytes] - 1) << 4) & 0xF0);
}
// the last 1.5 bytes are always the disp
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, although in practice it will often be O(n^3) since one of the constants is 0x10110
/// (the maximum length of a compressed block)
/// </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>
internal static 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) and 0x10110 constant.
// however since a lot of files will not be larger than 0x10110, this will often take ~O(n^2) time.
// be sure to bound the input length with 0x10110, as that's the maximum length for LZ-11 compressed blocks.
int maxLen = LZUtil.GetOccurrenceLength(indata + i, Math.Min(inLength - i, 0x10110),
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 blocklen;
if (j > 0x110)
blocklen = 4;
else if (j > 0x10)
blocklen = 3;
else
blocklen = 2;
int newCompLen;
if (i + j >= inLength)
newCompLen = blocklen;
else
newCompLen = blocklen + 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
#endregion
}
#region Exceptions
/// <summary>
/// An exception indicating that the file cannot be compressed, because the decompressed size
/// cannot be represented in the current compression format.
/// </summary>
public class InputTooLargeException : Exception
{
/// <summary>
/// Creates a new exception that indicates that the input is too big to be compressed.
/// </summary>
public InputTooLargeException()
: base("The compression ratio is not high enough to fit the input "
+ "in a single compressed file.") { }
}
/// <summary>
/// An exception that is thrown by the decompression functions when there
/// is not enough data available in order to properly decompress the input.
/// </summary>
public class NotEnoughDataException : IOException
{
/// <summary>
/// Gets the actual number of written bytes.
/// </summary>
public long WrittenLength { get; }
/// <summary>
/// Gets the number of bytes that was supposed to be written.
/// </summary>
public long DesiredLength { get; }
/// <summary>
/// Creates a new NotEnoughDataException.
/// </summary>
/// <param name="currentOutSize">The actual number of written bytes.</param>
/// <param name="totalOutSize">The desired number of written bytes.</param>
public NotEnoughDataException(long currentOutSize, long totalOutSize)
: base("Not enough data availble; 0x" + currentOutSize.ToString("X")
+ " of " + (totalOutSize < 0 ? "???" : "0x" + totalOutSize.ToString("X"))
+ " bytes written.")
{
WrittenLength = currentOutSize;
DesiredLength = totalOutSize;
}
}
/// <summary>
/// An exception thrown by the compression or decompression function, indicating that the
/// given input length was too large for the given input stream.
/// </summary>
public class StreamTooShortException : EndOfStreamException
{
/// <summary>
/// Creates a new exception that indicates that the stream was shorter than the given input length.
/// </summary>
public StreamTooShortException()
: base("The end of the stream was reached "
+ "before the given amout of data was read.")
{ }
}
/// <summary>
/// An exception indication that the input has more data than required in order
/// to decompress it. This may indicate that more sub-files are present in the file.
/// </summary>
public class TooMuchInputException : Exception
{
/// <summary>
/// Gets the number of bytes read by the decompressed to decompress the stream.
/// </summary>
public long ReadBytes { get; private set; }
/// <summary>
/// Creates a new exception indicating that the input has more data than necessary for
/// decompressing th stream. It may indicate that other data is present after the compressed
/// stream.
/// </summary>
/// <param name="readBytes">The number of bytes read by the decompressor.</param>
/// <param name="totLength">The indicated length of the input stream.</param>
public TooMuchInputException(long readBytes, long totLength)
: base("The input contains more data than necessary. Only used 0x"
+ readBytes.ToString("X") + " of 0x" + totLength.ToString("X") + " bytes")
{
ReadBytes = readBytes;
}
}
#endregion
#region Supplementary
/// <summary>
/// Class for I/O-related utility methods.
/// </summary>
public static class LZUtil
{
/// <summary>
/// Determine the maximum size of a LZ-compressed block starting at newPtr, using the already compressed data
/// starting at oldPtr. Takes O(inLength * oldLength) = O(n^2) time.
/// </summary>
/// <param name="newPtr">The start of the data that needs to be compressed.</param>
/// <param name="newLength">The number of bytes that still need to be compressed.
/// (or: the maximum number of bytes that _may_ be compressed into one block)</param>
/// <param name="oldPtr">The start of the raw file.</param>
/// <param name="oldLength">The number of bytes already compressed.</param>
/// <param name="disp">The offset of the start of the longest block to refer to.</param>
/// <param name="minDisp">The minimum allowed value for 'disp'.</param>
/// <returns>The length of the longest sequence of bytes that can be copied from the already decompressed data.</returns>
public static unsafe int GetOccurrenceLength(byte* newPtr, int newLength, byte* oldPtr, int oldLength, out int disp, int minDisp = 1)
{
disp = 0;
if (newLength == 0)
return 0;
int maxLength = 0;
// try every possible 'disp' value (disp = oldLength - i)
for (int i = 0; i < oldLength - minDisp; i++)
{
// work from the start of the old data to the end, to mimic the original implementation's behaviour
// (and going from start to end or from end to start does not influence the compression ratio anyway)
byte* currentOldStart = oldPtr + i;
int currentLength = 0;
// determine the length we can copy if we go back (oldLength - i) bytes
// always check the next 'newLength' bytes, and not just the available 'old' bytes,
// as the copied data can also originate from what we're currently trying to compress.
for (int j = 0; j < newLength; j++)
{
// stop when the bytes are no longer the same
if (*(currentOldStart + j) != *(newPtr + j))
break;
currentLength++;
}
// update the optimal value
if (currentLength > maxLength)
{
maxLength = currentLength;
disp = oldLength - i;
// if we cannot do better anyway, stop trying.
if (maxLength == newLength)
break;
}
}
return maxLength;
}
}
public static class IOUtils
{
#region byte[] <-> (u)int
/// <summary>
/// Returns a 4-byte unsigned integer as used on the NDS converted from four bytes
/// at a specified position in a byte array.
/// </summary>
/// <param name="buffer">The source of the data.</param>
/// <param name="offset">The location of the data in the source.</param>
/// <returns>The indicated 4 bytes converted to uint</returns>
public static uint ToNDSu32(byte[] buffer, int offset)
{
return (uint)(buffer[offset]
| (buffer[offset + 1] << 8)
| (buffer[offset + 2] << 16)
| (buffer[offset + 3] << 24));
}
/// <summary>
/// Returns a 4-byte signed integer as used on the NDS converted from four bytes
/// at a specified position in a byte array.
/// </summary>
/// <param name="buffer">The source of the data.</param>
/// <param name="offset">The location of the data in the source.</param>
/// <returns>The indicated 4 bytes converted to int</returns>
public static int ToNDSs32(byte[] buffer, int offset)
{
return buffer[offset]
| (buffer[offset + 1] << 8)
| (buffer[offset + 2] << 16)
| (buffer[offset + 3] << 24);
}
/// <summary>
/// Converts a u32 value into a sequence of bytes that would make ToNDSu32 return
/// the given input value.
/// </summary>
public static byte[] FromNDSu32(uint value)
{
return new[] {
(byte)(value & 0xFF),
(byte)((value >> 8) & 0xFF),
(byte)((value >> 16) & 0xFF),
(byte)((value >> 24) & 0xFF)
};
}
/// <summary>
/// Returns a 3-byte integer as used in the built-in compression
/// formats in the DS, converted from three bytes at a specified position in a byte array,
/// </summary>
/// <param name="buffer">The source of the data.</param>
/// <param name="offset">The location of the data in the source.</param>
/// <returns>The indicated 3 bytes converted to an integer.</returns>
public static int ToNDSu24(byte[] buffer, int offset)
{
return buffer[offset]
| (buffer[offset + 1] << 8)
| (buffer[offset + 2] << 16);
}
#endregion
}
#endregion
}
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