LZ4 压缩 (C++) 和解压缩 (Java)

Question

My objective is to compress a file using LZ4 in C++ and to decompress it in Java.

My text file (A.txt):

Hi, Hello everyone.
Thanks.

The file after c++ compression (A.txt.lz4):

"M@Pw  €Hi, Hello everyone.
Thanks.

Then I decompressed it in Java (B.txt):

i, Hello everyone.
Thanks.                                             

The problem is I'm not getting the first character of every file. I can't figure out where I'm going wrong.

My java code:

public static void uncompressLz4File(String str1, String str2) {
File f1 = new File(str1);
File f2 = new File(str2);
try (InputStream fin = Files.newInputStream(f1.toPath());
        BufferedInputStream in = new BufferedInputStream(fin);
        OutputStream out = Files.newOutputStream(Paths.get(f2.getAbsolutePath()));
        FramedLZ4CompressorInputStream zIn = new FramedLZ4CompressorInputStream(in))
{
    int n;
    zIn.getCompressedCount();
    byte[] b = new byte[1];
    int uncompressedLength = zIn.read(b, 0, 1) == -1 ? -1 : b[0] & 255;
    b[0] = (byte) uncompressedLength;
    final byte[] buffer = new byte[uncompressedLength];
    while (-1 != (n = zIn.read(buffer)))
    {
        out.write(buffer);
    }
}
catch (Exception e)
{
    
}
}

public static void main(String args[]) throws IOException
{
    String str1 = "C:\\Users\\aravinth\\Desktop\\A.txt.lz4";
    String str2 = "C:\\Users\\aravinth\\Desktop\\B.txt";
    uncompressLz4File(str1, str2);  
}

Any help would be useful. Thanks in advance.

Answer 1

There is a factory for creating streams that should take care of the check:

CompressorInputStream zIn =
    new CompressorStreamFactory()
    .createCompressorInputStream(CompressorStreamFactory.LZ4_BLOCK, in);

or LZ4_FRAMED depending on what the C++ library generates.

Answer 2

Thanks everyone for the help. I fixed it using this code.

public static void uncompressLz4File(String str1, String str2) {
    File f1 = new File(str1);
    File f2 = new File(str2);
    try (FileInputStream fin = new FileInputStream(f1);
            BufferedInputStream in = new BufferedInputStream(fin);
            OutputStream out = Files.newOutputStream(Paths.get(f2.getAbsolutePath()));
            FramedLZ4CompressorInputStream zIn = new FramedLZ4CompressorInputStream(in)) {
        int n;
        byte[] b = new byte[1024];
        while ((n = zIn.read(b)) > 0) {
            out.write(b, 0, n);
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}