rc Rand/crypto utility

user/rc/rr.c

@@ -0,0 +1,50 @@
+#include <stddef.h>
+#include <stdint.h>
+#include <ulib.h>
+
+int32_t rr(int32_t min, int32_t max) {
+  if (max <= min)
+    return min;
+
+  uint32_t range = (uint32_t)(max - min + 1);
+  uint32_t val;
+  int32_t rnd;
+
+  for (size_t i = 0; i < 10; i++) {
+    rnd = rand();
+    if (rnd == -1)
+      continue;
+
+    val = (uint32_t)rnd;
+
+    uint32_t limit = (uint32_t)(-range) % range;
+    if (val >= limit) {
+      return min + (val % range);
+    }
+  }
+
+  return -1;
+}
+
+void rc_rr(void) {
+  if (argslen() < 3) {
+    uprintf("rc: Not enough arguments\n");
+    return;
+  }
+
+  char *beginstr = *(args()+1);
+  char *endstr = *(args()+2);
+
+  char *endb;
+  long begin = string_conv_strtol(beginstr, &endb, 10);
+  char *ende;
+  long end = string_conv_strtol(endstr, &ende, 10);
+
+  int32_t r = rr(begin, end);
+  if (rr == -1) {
+    uprintf("rc: failed to generate random number in range\n");
+    return;
+  }
+
+  uprintf("%d\n", r);
+}