Merge branch 'master' of github.com:jtsiomb/pcboot

[bootcensus] / src / libc / math.c

diff --git a/src/libc/math.c b/src/libc/math.c
new file mode 100644 (file)
index 0000000..3f3e5de
--- /dev/null
+++ b/src/libc/math.c
@@ -0,0 +1,55 @@
+/*
+pcboot - bootable PC demo/game kernel
+Copyright (C) 2018-2019  John Tsiombikas <nuclear@member.fsf.org>
+
+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, either version 3 of the License, or
+(at your option) any later version.
+
+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, see <https://www.gnu.org/licenses/>.
+*/
+#include "math.h"
+
+static double calc_pow(double x, double y, double precision);
+
+double pow(double x, double y)
+{
+       if(y == 0.0 || y == -0.0) {
+               return 1.0;
+       }
+       if(y == 1.0) {
+               return x;
+       }
+       if(y == -INFINITY) {
+               return fabs(x) < 1.0 ? INFINITY : 0.0;
+       }
+       if(y == INFINITY) {
+               return fabs(x) < 1.0 ? 0.0 : INFINITY;
+       }
+       return calc_pow(x, y, 1e-6);
+}
+
+static double calc_pow(double x, double y, double precision)
+{
+       if(y < 0.0) {
+               return 1.0 / calc_pow(x, -y, precision);
+       }
+       if(y >= 10.0) {
+               double p = calc_pow(x, y / 2.0, precision / 2.0);
+               return p * p;
+       }
+       if(y >= 1.0) {
+               return x * calc_pow(x, y - 1.0, precision);
+       }
+       if(precision >= 1) {
+               return __builtin_sqrt(x);
+       }
+       return __builtin_sqrt(calc_pow(x, y * 2.0, precision * 2.0));
+}