presto-orc/src/main/java/io/prestosql/orc/stream/LongDecode.java/LongDecode/readSignedVInt
class LongDecode:    public static long readSignedVInt(OrcInputStream inputStream)
            throws IOException
    {
        long result = readUnsignedVInt(inputStream);
        return zigzagDecode(result);
    }