presto-rcfile/src/main/java/io/prestosql/rcfile/RcFileDecoderUtils.java/RcFileDecoderUtils/readVIntInternal
class RcFileDecoderUtils:    private static long readVIntInternal(Slice slice, int start, int length)
    {
        long value = 0;
        for (int i = 1; i < length; i++) {
            value <<= 8;
            value |= (slice.getByte(start + i) & 0xFF);
        }
        return isNegativeVInt(slice.getByte(start)) ? ~value : value;
    }