mirror of
https://github.com/Barubary/dsdecmp.git
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284 lines
13 KiB
C#
284 lines
13 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
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{
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/// <summary>
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/// The LZ-Overlay compression format. Compresses part of the file from end to start.
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/// Is used for the 'overlay' files in NDS games, as well as arm9.bin.
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/// Note that the last 12 bytes should not be included in the 'inLength' argument when
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/// decompressing arm9.bin. This is done automatically if a file is given instead of a stream.
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/// </summary>
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public class LZOvl : CompressionFormat
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{
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#region Method: Supports(string file)
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public override bool Supports(string file)
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{
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using (FileStream fstr = File.OpenRead(file))
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{
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long fLength = fstr.Length;
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// arm9.bin is special in the sense that the last 12 bytes should/can be ignored.
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if (Path.GetFileName(file) == "arm9.bin")
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fLength -= 0xC;
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return this.Supports(fstr, fLength);
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}
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}
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#endregion
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#region Method: Supports(Stream, long)
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public override bool Supports(System.IO.Stream stream, long inLength)
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{
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// assume the 'inLength' does not include the 12 bytes at the end of arm9.bin
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// only allow integer-sized files
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if (inLength > 0xFFFFFFFFL)
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return false;
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// the header is 4 bytes minimum
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if (inLength < 4)
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return false;
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long streamStart = stream.Position;
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byte[] header = new byte[Math.Min(inLength, 0x20)];
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stream.Position += inLength - header.Length;
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stream.Read(header, 0, header.Length);
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// reset the stream
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stream.Position = streamStart;
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uint extraSize = IOUtils.ToNDSu32(header, header.Length - 4);
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if (extraSize == 0)
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return true;
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// if the extrasize is nonzero, the minimum header length is 8 bytes
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if (header.Length < 8)
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return false;
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byte headerLen = header[header.Length - 5];
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if (inLength < headerLen)
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return false;
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// the compressed length should fit in the input file
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int compressedLen = header[header.Length - 6] << 16
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| header[header.Length - 7] << 8
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| header[header.Length - 8];
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if (compressedLen >= inLength - headerLen)
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return false;
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// verify that the rest of the header is filled with 0xFF
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for (int i = header.Length - 9; i >= header.Length - headerLen; i--)
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if (header[i] != 0xFF)
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return false;
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return true;
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}
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#endregion
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#region Method: Decompress(string, string)
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public override void Decompress(string infile, string outfile)
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{
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// make sure the output directory exists
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string outDirectory = Path.GetDirectoryName(outfile);
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if (!Directory.Exists(outDirectory))
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Directory.CreateDirectory(outDirectory);
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// open the two given files, and delegate to the format-specific code.
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using (FileStream inStream = new FileStream(infile, FileMode.Open),
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outStream = new FileStream(outfile, FileMode.Create))
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{
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long fLength = inStream.Length;
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// arm9.bin needs special attention
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if (Path.GetFileName(infile) == "arm9.bin")
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fLength -= 0xC;
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this.Decompress(inStream, fLength, outStream);
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}
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}
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#endregion
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public override long Decompress(System.IO.Stream instream, long inLength, System.IO.Stream outstream)
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{
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#region Format description
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// Overlay LZ compression is basically just LZ-0x10 compression.
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// however the order if reading is reversed: the compression starts at the end of the file.
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// Assuming we start reading at the end towards the beginning, the format is:
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/*
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* u32 extraSize; // decompressed data size = file length (including header) + this value
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* u8 headerSize;
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* u24 compressedLength; // can be less than file size (w/o header). If so, the rest of the file is uncompressed.
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* u8[headerSize-8] padding; // 0xFF-s
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*
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* 0x10-like-compressed data follows (without the usual 4-byte header).
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* The only difference is that 2 should be added to the DISP value in compressed blocks
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* to get the proper value.
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* the u32 and u24 are read most significant byte first.
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* if extraSize is 0, there is no headerSize, decompressedLength or padding.
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* the data starts immediately, and is uncompressed.
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*
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* arm9.bin has 3 extra u32 values at the 'start' (ie: end of the file),
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* which may be ignored. (and are ignored here) These 12 bytes also should not
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* be included in the computation of the output size.
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*/
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#endregion
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#region First read the last 4 bytes of the stream (the 'extraSize')
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// first go to the end of the stream, since we're reading from back to front
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// read the last 4 bytes, the 'extraSize'
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instream.Position += inLength - 4;
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byte[] buffer = new byte[4];
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try
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{
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instream.Read(buffer, 0, 4);
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}
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catch (System.IO.EndOfStreamException)
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{
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// since we're immediately checking the end of the stream,
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// this is the only location where we have to check for an EOS to occur.
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throw new StreamTooShortException();
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}
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uint extraSize = IOUtils.ToNDSu32(buffer, 0);
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#endregion
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// if the extra size is 0, there is no compressed part, and the header ends there.
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if (extraSize == 0)
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{
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#region just copy the input to the output
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// first go back to the start of the file. the current location is after the 'extraSize',
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// and thus at the end of the file.
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instream.Position -= inLength;
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// no buffering -> slow
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buffer = new byte[inLength - 4];
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instream.Read(buffer, 0, (int)(inLength - 4));
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outstream.Write(buffer, 0, (int)(inLength - 4));
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// make sure the input is positioned at the end of the file
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instream.Position += 4;
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return inLength - 4;
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#endregion
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}
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else
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{
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// get the size of the compression header first.
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instream.Position -= 5;
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int headerSize = instream.ReadByte();
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// then the compressed data size.
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instream.Position -= 4;
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instream.Read(buffer, 0, 3);
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int compressedSize = buffer[0] | (buffer[1] << 8) | (buffer[2] << 16);
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#region copy the non-compressed data
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// copy the non-compressed data first.
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buffer = new byte[inLength - headerSize - compressedSize];
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instream.Position -= (inLength - 5);
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instream.Read(buffer, 0, buffer.Length);
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outstream.Write(buffer, 0, buffer.Length);
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#endregion
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// buffer the compressed data, such that we don't need to keep
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// moving the input stream position back and forth
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buffer = new byte[compressedSize];
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instream.Read(buffer, 0, compressedSize);
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// we're filling the output from end to start, so we can't directly write the data.
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// buffer it instead (also use this data as buffer instead of a ring-buffer for
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// decompression)
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byte[] outbuffer = new byte[compressedSize + headerSize + extraSize];
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int currentOutSize = 0;
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int decompressedLength = outbuffer.Length;
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int readBytes = 0;
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byte flags = 0, mask = 1;
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while (currentOutSize < decompressedLength)
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{
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// (throws when requested new flags byte is not available)
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#region Update the mask. If all flag bits have been read, get a new set.
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// the current mask is the mask used in the previous run. So if it masks the
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// last flag bit, get a new flags byte.
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if (mask == 1)
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{
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if (readBytes >= compressedSize)
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throw new NotEnoughDataException(currentOutSize, decompressedLength);
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flags = buffer[buffer.Length - 1 - readBytes]; readBytes++;
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mask = 0x80;
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}
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else
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{
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mask >>= 1;
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}
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#endregion
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// bit = 1 <=> compressed.
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if ((flags & mask) > 0)
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{
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// (throws when < 2 bytes are available)
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#region Get length and displacement('disp') values from next 2 bytes
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// there are < 2 bytes available when the end is at most 1 byte away
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if (readBytes + 1 >= inLength)
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{
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throw new NotEnoughDataException(currentOutSize, decompressedLength);
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}
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int byte1 = buffer[compressedSize - 1 - readBytes]; readBytes++;
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int byte2 = buffer[compressedSize - 1 - readBytes]; readBytes++;
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// the number of bytes to copy
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int length = byte1 >> 4;
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length += 3;
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// from where the bytes should be copied (relatively)
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int disp = ((byte1 & 0x0F) << 8) | byte2;
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disp += 3;
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if (disp > currentOutSize)
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{
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if (currentOutSize < 2)
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throw new InvalidDataException("Cannot go back more than already written; "
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+ "attempt to go back 0x" + disp.ToString("X") + " when only 0x"
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+ currentOutSize.ToString("X") + " bytes have been written.");
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// HACK. this seems to produce valid files, but isn't the most elegant solution.
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// although this _could_ be the actual way to use a disp of 2 in this format,
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// as otherwise the minimum would be 3 (and 0 is undefined, and 1 is less useful).
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disp = 2;
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}
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#endregion
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int bufIdx = currentOutSize - disp;
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for (int i = 0; i < length; i++)
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{
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byte next = outbuffer[outbuffer.Length - 1 - bufIdx];
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bufIdx++;
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outbuffer[outbuffer.Length - 1 - currentOutSize] = next;
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currentOutSize++;
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}
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}
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else
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{
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if (readBytes >= inLength)
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throw new NotEnoughDataException(currentOutSize, decompressedLength);
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byte next = buffer[buffer.Length - 1 - readBytes]; readBytes++;
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outbuffer[outbuffer.Length - 1 - currentOutSize] = next;
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currentOutSize++;
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}
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}
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// write the decompressed data
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outstream.Write(outbuffer, 0, outbuffer.Length);
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// make sure the input is positioned at the end of the file; the stream is currently
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// at the compression header.
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instream.Position += headerSize;
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return decompressedLength + (inLength - headerSize - compressedSize);
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}
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}
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public override int Compress(System.IO.Stream instream, long inLength, System.IO.Stream outstream)
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{
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throw new NotImplementedException();
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}
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}
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}
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