Fold LIBC_RAND into LIBC_STDIO/TINYMATH/INTRIN

libc/stdio/vigna.c

@@ -0,0 +1,78 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/stdio/rand.h"
+
+static uint64_t g_vigna;
+
+/**
+ * Returns deterministic pseudorandom data, e.g.
+ *
+ *     uint64_t x = vigna();
+ *
+ * You can generate different types of numbers as follows:
+ *
+ *     int64_t x = vigna() >> 1;    // make positive signed integer
+ *     double x = _real1(vigna());  // make float on [0,1]-interval
+ *
+ * You can seed this random number generator using:
+ *
+ *     svigna(rdseed());
+ *
+ * You may use the reentrant version of this function:
+ *
+ *     static uint64_t s = 0;
+ *     uint64_t x = svigna_r(&s);
+ *
+ * If you want to fill a buffer with data then rngset() implements
+ * vigna's algorithm to do that extremely well:
+ *
+ *     char buf[4096];
+ *     rngset(buf, sizeof(buf), vigna, 0);
+ *
+ * If you want a fast pseudorandom number generator that seeds itself
+ * automatically on startup and fork() then consider rand64(). If you
+ * want true random data then consider rdseed, rdrand, and getrandom.
+ *
+ * @return 64 bits of pseudorandom data
+ * @note this function is not intended for cryptography
+ * @note this function passes bigcrush and practrand
+ * @note this function takes at minimum 4 cycles
+ */
+uint64_t vigna(void) {
+  return vigna_r(&g_vigna);
+}
+
+/**
+ * Returns pseudorandom data.
+ * @see vigna() for easy api
+ */
+uint64_t vigna_r(uint64_t state[hasatleast 1]) {
+  uint64_t z = (state[0] += 0x9e3779b97f4a7c15);
+  z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
+  z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
+  return z ^ (z >> 31);
+}
+
+/**
+ * Seeds vigna() pseudorandom number generator.
+ * @see vigna(), vigna_r()
+ */
+void svigna(uint64_t seed) {
+  g_vigna = seed;
+}