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-rw-r--r--libc/stdlib/rand_r.c48
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;
+}