diff options
Diffstat (limited to 'libc/stdlib/rand_r.c')
-rw-r--r-- | libc/stdlib/rand_r.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/libc/stdlib/rand_r.c b/libc/stdlib/rand_r.c new file mode 100644 index 000000000..610044083 --- /dev/null +++ b/libc/stdlib/rand_r.c @@ -0,0 +1,48 @@ +/* Reentrant random function frm POSIX.1c. + Copyright (C) 1996, 1999 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@cygnus.com <mailto:drepper@cygnus.com>>, 1996. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <stdlib.h> + + +/* This algorithm is mentioned in the ISO C standard, here extended + for 32 bits. */ +int rand_r (unsigned int *seed) +{ + unsigned int next = *seed; + int result; + + next *= 1103515245; + next += 12345; + result = (unsigned int) (next / 65536) % 2048; + + next *= 1103515245; + next += 12345; + result <<= 10; + result ^= (unsigned int) (next / 65536) % 1024; + + next *= 1103515245; + next += 12345; + result <<= 10; + result ^= (unsigned int) (next / 65536) % 1024; + + *seed = next; + + return result; +} |