diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 40d71cfdec32..f5d71f0ead59 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -398,40 +398,44 @@ static void vc_uniscr_clear_lines(struct vc_data *vc, unsigned int y, memset32(vc->vc_uni_lines[y++], ' ', vc->vc_cols); } +/* juggling array rotation algorithm (complexity O(N), size complexity O(1)) */ +static void juggle_array(u32 **array, unsigned int size, unsigned int nr) +{ + unsigned int gcd_idx; + + for (gcd_idx = 0; gcd_idx < gcd(nr, size); gcd_idx++) { + u32 *gcd_idx_val = array[gcd_idx]; + unsigned int dst_idx = gcd_idx; + + while (1) { + unsigned int src_idx = (dst_idx + nr) % size; + if (src_idx == gcd_idx) + break; + + array[dst_idx] = array[src_idx]; + dst_idx = src_idx; + } + + array[dst_idx] = gcd_idx_val; + } +} + static void vc_uniscr_scroll(struct vc_data *vc, unsigned int t, unsigned int b, enum con_scroll dir, unsigned int nr) { u32 **uni_lines = vc->vc_uni_lines; - unsigned int i, j, k, sz, d, clear; + unsigned int size = b - t; if (!uni_lines) return; - sz = b - t; - clear = b - nr; - d = nr; - if (dir == SM_DOWN) { - clear = t; - d = sz - nr; + juggle_array(&uni_lines[top], size, size - nr); + vc_uniscr_clear_lines(vc, t, nr); + } else { + juggle_array(&uni_lines[top], size, nr); + vc_uniscr_clear_lines(vc, b - nr, nr); } - - for (i = 0; i < gcd(d, sz); i++) { - u32 *tmp = uni_lines[t + i]; - j = i; - while (1) { - k = j + d; - if (k >= sz) - k -= sz; - if (k == i) - break; - uni_lines[t + j] = uni_lines[t + k]; - j = k; - } - uni_lines[t + j] = tmp; - } - - vc_uniscr_clear_lines(vc, clear, nr); } static void vc_uniscr_copy_area(u32 **dst_lines,