Badrand pseudo random number generator, emphasis on pseudo

kern/libkern/badrand.c

@@ -0,0 +1,35 @@
+#include "badrand.h"
+#include <stdint.h>
+
+#define PRAND_BUILD_SEED                                                                                               \
+    ((uint64_t)(__TIME__[0]) * (uint64_t)(__TIME__[1]) * (uint64_t)(__TIME__[3]) * (uint64_t)(__TIME__[4]) *           \
+     (uint64_t)(__TIME__[6]) * (uint64_t)(__TIME__[7]))
+
+static uint64_t seed = PRAND_BUILD_SEED * 6364136223846793005ULL + 1;
+
+uint64_t badrand() {
+    seed = seed * 6364136223846793005ULL + 1;
+    return seed;
+}
+
+uint64_t badrand_range(uint64_t min, uint64_t max) {
+    uint64_t range = max - min + 1;
+    uint64_t x;
+    uint64_t limit = UINT64_MAX - (UINT64_MAX % range);
+
+    do {
+        x = badrand();
+    } while (x > limit);
+
+    return min + (x % range);
+}
+
+void sbadprand(uint64_t s) {
+    if (s) {
+        seed ^= (s * 0x9e3779b97f4a7c15ULL) + (seed << 6) + (seed >> 2);
+    } else {
+        seed ^= PRAND_BUILD_SEED;
+    }
+}
+
+#undef PRAND_BUILD_SEED