random.c: rb_random_ulong_limited

* random.c (rb_random_ulong_limited): new function to return a random
  value from 0 upto limit as unsigned long, simillary to
  rb_genrand_ulong_limited but with arbitrary RNG object.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37125 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 16 insertions, 0 deletions

diff --git a/random.c b/random.c
index b36784c405..ccae2a0178 100644
--- a/random.c
+++ b/random.c
@@ -943,6 +943,22 @@ rb_random_real(VALUE obj)
     return genrand_real(&rnd->mt);
 }
 
+unsigned long
+rb_random_ulong_limited(VALUE obj, unsigned long limit)
+{
+    rb_random_t *rnd = try_get_rnd(obj);
+    if (!rnd) {
+	VALUE lim = ULONG2NUM(limit);
+	VALUE v = rb_funcall2(obj, id_rand, 1, &lim);
+	unsigned long r = NUM2ULONG(v);
+	if (r > limit) {
+	    rb_raise(rb_eRangeError, "random number too big %ld", r);
+	}
+	return r;
+    }
+    return limited_rand(&rnd->mt, limit);
+}
+
 /*
  * call-seq: prng.bytes(size) -> a_string
  *