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C#: implemented the LZ-Overlay decompression in the new structure. (still untested again).

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barubary 2011-04-21 11:52:09 +00:00
parent 426f89f37c
commit 80efded10b
1 changed files with 158 additions and 1 deletions
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159
CSharp/DSDecmp/Formats/LZOvl.cs
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@ -1,6 +1,7 @@
using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
namespace DSDecmp.Formats
{
@ -57,6 +58,7 @@ namespace DSDecmp.Formats
public override void Decompress(System.IO.Stream instream, long inLength, System.IO.Stream outstream)
{
#region Format description
// Overlay LZ compression is basically just LZ-0x10 compression.
// however the order if reading is reversed: the compression starts at the end of the file.
// Assuming we start reading at the end towards the beginning, the format is:
@ -77,7 +79,162 @@ namespace DSDecmp.Formats
* which may be ignored. (and are ignored here) These 12 bytes also should not
* be included in the computation of the output size.
*/
throw new NotImplementedException();
#endregion
#region First read the last 4 bytes of the stream (the 'extraSize')
// first go to the end of the stream, since we're reading from back to front
// read the last 4 bytes, the 'extraSize'
instream.Position += inLength - 4;
byte[] buffer = new byte[4];
try
{
instream.Read(buffer, 0, 4);
}
catch (System.IO.EndOfStreamException)
{
// since we're immediately checking the end of the stream,
// this is the only location where we have to check for an EOS to occur.
throw new StreamTooShortException();
}
uint extraSize = IOUtils.ToNDSu32(buffer, 0);
#endregion
// if the extra size is 0, there is no compressed part, and the header ends there.
if (extraSize == 0)
{
#region just copy the input to the output
// first go back to the start of the file. the current location is after the 'extraSize',
// and thus at the end of the file.
instream.Position -= inLength;
// no buffering -> slow
buffer = new byte[inLength - 4];
instream.Read(buffer, 0, (int)(inLength - 4));
outstream.Write(buffer, 0, (int)(inLength - 4));
// make sure the input is positioned at the end of the file
instream.Position += 4;
#endregion
}
else
{
// get the size of the compression header first.
instream.Position -= 5;
int headerSize = instream.ReadByte();
// then the compressed data size.
instream.Position -= 4;
instream.Read(buffer, 0, 3);
int compressedSize = buffer[0] | (buffer[1] << 8) | (buffer[2] << 16);
#region copy the non-compressed data
// copy the non-compressed data first.
buffer = new byte[inLength - headerSize - compressedSize];
instream.Position -= (inLength - 5);
instream.Read(buffer, 0, buffer.Length);
outstream.Write(buffer, 0, buffer.Length);
#endregion
// buffer the compressed data, such that we don't need to keep
// moving the input stream position back and forth
buffer = new byte[compressedSize];
instream.Read(buffer, 0, compressedSize);
// we're filling the output from end to start, so we can't directly write the data.
// buffer it instead (also use this data as buffer instead of a ring-buffer for
// decompression)
byte[] outbuffer = new byte[compressedSize + headerSize + extraSize];
int currentOutSize = 0;
int decompressedLength = outbuffer.Length;
int readBytes = 0;
byte flags = 0, mask = 1;
while (currentOutSize < decompressedLength)
{
// (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 >= compressedSize)
throw new NotEnoughDataException(currentOutSize, decompressedLength);
flags = buffer[buffer.Length - 1 - readBytes]; readBytes++;
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)
{
throw new NotEnoughDataException(currentOutSize, decompressedLength);
}
int byte1 = buffer[compressedSize - 1 - readBytes]; readBytes++;
int byte2 = buffer[compressedSize - 1 - readBytes]; readBytes++;
// 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 += 3;
if (disp > currentOutSize)
{
if (currentOutSize < 2)
throw new InvalidDataException("Cannot go back more than already written; "
+ "attempt to go back 0x" + disp.ToString("X") + " when only 0x"
+ currentOutSize.ToString("X") + " bytes have been written.");
// HACK. this seems to produce valid files, but isn't the most elegant solution.
// although this _could_ be the actual way to use a disp of 2 in this format,
// as otherwise the minimum would be 3 (and 0 is undefined, and 1 is less useful).
disp = 2;
}
#endregion
int bufIdx = currentOutSize - disp;
for (int i = 0; i < length; i++)
{
byte next = outbuffer[outbuffer.Length - 1 - bufIdx];
bufIdx++;
outbuffer[outbuffer.Length - 1 - currentOutSize] = next;
currentOutSize++;
}
}
else
{
if (readBytes >= inLength)
throw new NotEnoughDataException(currentOutSize, decompressedLength);
byte next = buffer[buffer.Length - 1 - readBytes]; readBytes++;
outbuffer[outbuffer.Length - 1 - currentOutSize] = next;
currentOutSize++;
}
}
// write the decompressed data
outstream.Write(outbuffer, 0, outbuffer.Length);
// make sure the input is positioned at the end of the file; the stream is currently
// at the compression header.
instream.Position += headerSize;
}
}
public override int Compress(System.IO.Stream instream, long inLength, System.IO.Stream outstream)