update

pub fn update(self: *XxHash64, input: anytype) void {
    if (input.len < 32 - self.buf_len) {
        @memcpy(self.buf[self.buf_len..][0..input.len], input);
        self.buf_len += input.len;
        return;
    }

    var i: usize = 0;

    if (self.buf_len > 0) {
        i = 32 - self.buf_len;
        @memcpy(self.buf[self.buf_len..][0..i], input[0..i]);
        self.accumulator.processStripe(&self.buf);
        self.byte_count += self.buf_len;
    }

    i += self.accumulator.updateEmpty(input[i..], 32);
    self.byte_count += i;

    const remaining_bytes = input[i..];
    @memcpy(self.buf[0..remaining_bytes.len], remaining_bytes);
    self.buf_len = remaining_bytes.len;
}