Fold LIBC_RAND into LIBC_STDIO/TINYMATH/INTRIN

libc/stdio/rngset.c

@@ -0,0 +1,94 @@
+/*-*- 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 2020 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/calls/calls.h"
+#include "libc/dce.h"
+#include "libc/intrin/asan.internal.h"
+#include "libc/stdio/rand.h"
+#include "libc/stdio/stdio.h"
+
+/**
+ * Fills memory with random bytes, e.g.
+ *
+ *     char buf[512];
+ *     rngset(buf, sizeof(buf), 0, 0);
+ *
+ * If reseed is zero then the internal PRNG is disabled and bytes are
+ * simply copied in little-endian order from the seed function. If seed
+ * is NULL then the reseed parameter is used as the seed value for the
+ * internal PRNG. If seed!=NULL and reseed>8 then reseed is the number
+ * of bytes after which the seed() function should be called again, to
+ * freshen up the PRNG.
+ *
+ * The main advantage of this generator is that it produces data at 13
+ * gigabytes per second since Vigna's Algorithm vectorizes better than
+ * alternatives, going even faster than xorshift.
+ *
+ * @return original buf
+ */
+noasan void *rngset(void *b, size_t n, uint64_t seed(void), size_t reseed) {
+  size_t m;
+  uint64_t i, x, t = 0;
+  unsigned char *p = b;
+  if (IsAsan()) {
+    __asan_verify(b, n);
+  }
+  if (!seed) {
+    t = reseed;
+    reseed = -1;
+  } else if (reseed < 8) {
+    reseed = 8;
+  }
+  while (n) {
+    if (seed) t = seed();
+    if (!seed || reseed > 8) {
+      n -= (m = reseed < n ? reseed : n);
+      while (m >= 8) {
+        x = (t += 0x9e3779b97f4a7c15);
+        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
+        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
+        x = (x ^ (x >> 31));
+        __builtin_memcpy(p, &x, 8);
+        p += 8;
+        m -= 8;
+      }
+      while (m--) {
+        *p++ = t;
+        t >>= 8;
+      }
+    } else if (n >= 8) {
+      p[0] = (0x00000000000000FF & t) >> 000;
+      p[1] = (0x000000000000FF00 & t) >> 010;
+      p[2] = (0x0000000000FF0000 & t) >> 020;
+      p[3] = (0x00000000FF000000 & t) >> 030;
+      p[4] = (0x000000FF00000000 & t) >> 040;
+      p[5] = (0x0000FF0000000000 & t) >> 050;
+      p[6] = (0x00FF000000000000 & t) >> 060;
+      p[7] = (0xFF00000000000000 & t) >> 070;
+      p += 8;
+      n -= 8;
+    } else {
+      while (n) {
+        *p++ = t;
+        t >>= 8;
+        --n;
+      }
+    }
+  }
+  return b;
+}