LZMA Compression in Java

LZMA Compression in Java:

static void PrintHelp()
{
System.out.println(
“\nUsage:  LZMA <e|d> [<switches>...] inputFile outputFile\n” +
“  e: encode file\n” +
“  d: decode file\n” +
“  b: Benchmark\n” +
“<Switches>\n” +
// “  -a{N}:  set compression mode – [0, 1], default: 1 (max)\n” +
“  -d{N}:  set dictionary – [0,28], default: 23 (8MB)\n” +
“  -fb{N}: set number of fast bytes – [5, 273], default: 128\n” +
“  -lc{N}: set number of literal context bits – [0, 8], default: 3\n” +
“  -lp{N}: set number of literal pos bits – [0, 4], default: 0\n” +
“  -pb{N}: set number of pos bits – [0, 4], default: 2\n” +
“  -mf{MF_ID}: set Match Finder: [bt2, bt4], default: bt4\n” +
“  -eos:   write End Of Stream marker\n”
);
}

public static void main(String[] args) throws Exception
{
System.out.println(“\nLZMA (Java) 4.61  2008-11-23\n”);

if (args.length < 1)
{
PrintHelp();
return;
}

CommandLine params = new CommandLine();
if (!params.Parse(args))
{
System.out.println(“\nIncorrect command”);
return;
}

if (params.Command == CommandLine.kBenchmak)
{
int dictionary = (1 << 21);
if (params.DictionarySizeIsDefined)
dictionary = params.DictionarySize;
if (params.MatchFinder > 1)
throw new Exception(“Unsupported match finder”);
SevenZip.LzmaBench.LzmaBenchmark(params.NumBenchmarkPasses, dictionary);
}
else if (params.Command == CommandLine.kEncode || params.Command == CommandLine.kDecode)
{
java.io.File inFile = new java.io.File(params.InFile);
java.io.File outFile = new java.io.File(params.OutFile);

java.io.BufferedInputStream inStream  = new java.io.BufferedInputStream(new java.io.FileInputStream(inFile));
java.io.BufferedOutputStream outStream = new java.io.BufferedOutputStream(new java.io.FileOutputStream(outFile));

boolean eos = false;
if (params.Eos)
eos = true;
if (params.Command == CommandLine.kEncode)
{
SevenZip.Encoder encoder = new SevenZip.Encoder();
if (!encoder.SetAlgorithm(params.Algorithm))
throw new Exception(“Incorrect compression mode”);
if (!encoder.SetDictionarySize(params.DictionarySize))
throw new Exception(“Incorrect dictionary size”);
if (!encoder.SetNumFastBytes(params.Fb))
throw new Exception(“Incorrect -fb value”);
if (!encoder.SetMatchFinder(params.MatchFinder))
throw new Exception(“Incorrect -mf value”);
if (!encoder.SetLcLpPb(params.Lc, params.Lp, params.Pb))
throw new Exception(“Incorrect -lc or -lp or -pb value”);
encoder.SetEndMarkerMode(eos);
encoder.WriteCoderProperties(outStream);
long fileSize;
if (eos)
fileSize = -1;
else
fileSize = inFile.length();
for (int i = 0; i < 8; i++)
outStream.write((int)(fileSize >>> (8 * i)) & 0xFF);
encoder.Code(inStream, outStream, -1, -1, null);
}
else
{
int propertiesSize = 5;
byte[] properties = new byte[propertiesSize];
if (inStream.read(properties, 0, propertiesSize) != propertiesSize)
throw new Exception(“input .lzma file is too short”);
SevenZip.Decoder decoder = new SevenZip.Decoder();
if (!decoder.SetDecoderProperties(properties))
throw new Exception(“Incorrect stream properties”);
long outSize = 0;
for (int i = 0; i < 8; i++)
{
int v = inStream.read();
if (v < 0)
throw new Exception(“Can’t read stream size”);
outSize |= ((long)v) << (8 * i);
}
if (!decoder.Code(inStream, outStream, outSize))
throw new Exception(“Error in data stream”);
}
outStream.flush();
outStream.close();
inStream.close();
}
else
throw new Exception(“Incorrect command”);
return;
}