Gets the uncompressed size of this GZIPInputStream?

Question

I have a GZIPInputStream that I constructed from another ByteArrayInputStream. I want to know the original (uncompressed) length for the gzip data.

Answer 1

A more compact version of the calculation based on the 4 tail bytes (avoids using a byte buffer, calls Integer.reverseBytes to reverse the byte order of read bytes).

private static long getUncompressedSize(Path inputPath) throws IOException
{
    long size = -1;
    try (RandomAccessFile fp = new RandomAccessFile(inputPath.toFile(), "r")) {        
        fp.seek(fp.length() - Integer.BYTES);
        int n = fp.readInt();
        size = Integer.toUnsignedLong(Integer.reverseBytes(n));
    }
    return size;
}