defaultRebase

pub fn defaultRebase(w: *Writer, preserve: usize, minimum_len: usize) Error!void {
    while (w.buffer.len - w.end < minimum_len) {
        {
            // TODO: instead of this logic that "hides" data from
            // the implementation, introduce a seek index to Writer
            const preserved_head = w.end -| preserve;
            const preserved_tail = w.end;
            const preserved_len = preserved_tail - preserved_head;
            w.end = preserved_head;
            defer w.end += preserved_len;
            assert(0 == try w.vtable.drain(w, &.{""}, 1));
            assert(w.end <= preserved_head + preserved_len);
            @memmove(w.buffer[w.end..][0..preserved_len], w.buffer[preserved_head..preserved_tail]);
        }

        // If the loop condition was false this assertion would have passed
        // anyway. Otherwise, give the implementation a chance to grow the
        // buffer before asserting on the buffer length.
        assert(w.buffer.len - preserve >= minimum_len);
    }
}