altos: Bring up basic TeleTerra v0.2 UImultiarch

Lots of fun stuff here -- multiple panes of information.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/src/core/ao_sqrt.c b/src/core/ao_sqrt.c
new file mode 100644
index 00000000..09c2e319
--- /dev/null
+++ b/src/core/ao_sqrt.c
@@ -0,0 +1,46 @@
+/*
+ * Copyright © 2011 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "ao.h"
+
+/* Adapted from int_sqrt.c in the linux kernel, which is licensed GPLv2 */
+/**
+ * int_sqrt - rough approximation to sqrt
+ * @x: integer of which to calculate the sqrt
+ *
+ * A very rough approximation to the sqrt() function.
+ */
+
+uint32_t
+ao_sqrt(uint32_t op)
+{
+	uint32_t	res = 0;
+	uint32_t	one = 1UL << (sizeof (one) * 8 - 2);
+
+	while (one > op)
+		one >>= 2;
+
+	while (one != 0) {
+		if (op >= res + one) {
+			op = op - (res + one);
+			res = res +  2 * one;
+		}
+		res /= 2;
+		one /= 4;
+	}
+	return res;
+}