hphp/util/portability/rand_r.cpp

   1 // Borrowed from Musl Libc, under the following license:
   2 /*
   3  * Copyright ? 2005-2014 Rich Felker, et al.
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining
   6  * a copy of this software and associated documentation files (the
   7  * "Software"), to deal in the Software without restriction, including
   8  * without limitation the rights to use, copy, modify, merge, publish,
   9  * distribute, sublicense, and/or sell copies of the Software, and to
  10  * permit persons to whom the Software is furnished to do so, subject to
  11  * the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be
  14  * included in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  17  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  18  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  19  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  20  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  21  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  22  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24 #include "hphp/util/portability/rand_r.h"
  25
  26 static unsigned int temper(unsigned int x) {
  27   x ^= x >> 11;
  28   x ^= x << 7 & 0x9D2C5680;
  29   x ^= x << 15 & 0xEFC60000;
  30   x ^= x >> 18;
  31   return x;
  32 }
  33
  34 extern "C" int rand_r(unsigned int* seed) {
  35   return temper(*seed = *seed * 1103515245 + 12345) / 2;
  36 }