diff options
Diffstat (limited to 'lib/libc/stdlib/rand.c')
| -rw-r--r-- | lib/libc/stdlib/rand.c | 53 |
1 files changed, 52 insertions, 1 deletions
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 */ + |
