cii: Add arith impl

cii/src/arith.c

@@ -2,4 +2,36 @@
 // Use of this source is governed by GNU General Public License
 // that can be found in the LICENSE file.
 
-#include "cii/arith.h"
+#include "cii/arith.h"
+
+int arith_max(int x, int y) {
+  return (x > y) ? x : y;
+}
+
+int arith_min(int x, int y) {
+  return (x > y) ? y : x;
+}
+
+int arith_div(int x, int y) {
+  if ((-13 / 5 == -2) && ((x < 0) != (y < 0)) && (x % y != 0)) {
+    return x / y - 1;
+  } else {
+    return x / y;
+  }
+}
+
+int arith_mod(int x, int y) {
+  if ((-13 / 5 == -2) && ((x < 0) != (y < 0)) && (x % y != 0)) {
+    return x % y + y;
+  } else {
+    return x % y;
+  }
+}
+
+int arith_ceiling(int x, int y) {
+  return arith_div(x, y) + ( x % y != 0);
+}
+
+int arith_floor(int x, int y) {
+  return arith_div(x, y);
+}