Added Posix rand_r function.

2 files changed, 74 insertions, 5 deletions

diff --git a/lib/libc/stdlib/rand.3 b/lib/libc/stdlib/rand.3
index f2e3742..2aadd6c 100644
--- a/lib/libc/stdlib/rand.3
+++ b/lib/libc/stdlib/rand.3
@@ -35,12 +35,13 @@
 .\"
 .\"     @(#)rand.3	8.1 (Berkeley) 6/4/93
 .\"
-.Dd June 4, 1993
+.Dd May 25, 1999
 .Dt RAND 3
 .Os
 .Sh NAME
 .Nm rand ,
-.Nm srand
+.Nm srand ,
+.Nm rand_r
 .Nd bad random number generator
 .Sh SYNOPSIS
 .Fd #include <stdlib.h>
@@ -48,6 +49,8 @@
 .Fn srand "unsigned seed"
 .Ft int
 .Fn rand void
+.Ft int
+.Fn rand_r "unsigned *ctx"
 .Sh DESCRIPTION
 .Bf -symbolic
 These interfaces are obsoleted by random(3).
@@ -63,15 +66,26 @@ of 0 to
 .Pp
 The
 .Fn srand
-function sets its argument as the seed for a new sequence of
+function sets its argument
+.Fa seed
+as the seed for a new sequence of
 pseudo-random numbers to be returned by
 .Fn rand .
 These sequences are repeatable by calling
 .Fn srand
 with the same seed value.
 .Pp
-If no seed value is provided, the functions are automatically
+If no
+.Fa seed 
+value is provided, the functions are automatically
 seeded with a value of 1.
+.Pp
+.Fn rand_r
+provides the same functionality as
+.Fn rand .
+A pointer to the context value
+.Fa ctx
+must be supplied by the caller.
 .Sh SEE ALSO
 .Xr random 3
 .Sh STANDARDS
@@ -82,3 +96,7 @@ and
 functions
 conform to
 .St -ansiC .
+.Pp
+The
+.Fn rand_r
+function is as proposed in the POSIX.4a Draft #6 document.
diff --git a/lib/libc/stdlib/rand.c b/lib/libc/stdlib/rand.c
index 12846c3..94f6b50 100644
--- a/lib/libc/stdlib/rand.c
+++ b/lib/libc/stdlib/rand.c
@@ -29,6 +29,8 @@
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
+ *
+ * Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>.
  */
 
 #if defined(LIBC_SCCS) && !defined(lint)
@@ -38,12 +40,32 @@ static char sccsid[] = "@(#)rand.c	8.1 (Berkeley) 6/14/93";
 #include <sys/types.h>
 #include <stdlib.h>
 
+#ifdef TEST
+#include <stdio.h>
+#endif /* TEST */
+
+static int
+do_rand(unsigned long *ctx)
+{
+	return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1));
+}
+
+
+int
+rand_r(unsigned int *ctx)
+{
+	u_long val = (u_long) *ctx;
+	*ctx = do_rand(&val);
+	return (int) *ctx;
+}
+
+
 static u_long next = 1;
 
 int
 rand()
 {
-	return ((next = next * 1103515245 + 12345) % ((u_long)RAND_MAX + 1));
+	return do_rand(&next);
 }
 
 void
@@ -52,3 +74,32 @@ u_int seed;
 {
 	next = seed;
 }
+
+#ifdef TEST
+
+main()
+{
+    int i;
+    unsigned myseed;
+
+    printf("seeding rand with 0x19610910: \n");
+    srand(0x19610910);
+
+    printf("generating three pseudo-random numbers:\n");
+    for (i = 0; i < 3; i++)
+    {
+	printf("next random number = %d\n", rand());
+    }
+
+    printf("generating the same sequence with rand_r:\n");
+    myseed = 0x19610910;
+    for (i = 0; i < 3; i++)
+    {
+	printf("next random number = %d\n", rand_r(&myseed));
+    }
+
+    return 0;
+}
+
+#endif /* TEST */
+