improve srandomdev

[Ted Unangst]

If the user calls srandomdev(), they are asking for an unpredictable
sequence, even one that could not normally be produced. So give them
one. Use arc4random in that case.


Index: stdlib/random.c
===================================================================
RCS file: /cvs/src/lib/libc/stdlib/random.c,v
retrieving revision 1.22
diff -u -p -r1.22 random.c
--- stdlib/random.c     15 Jun 2014 05:10:58 -0000      1.22
+++ stdlib/random.c     13 Jul 2014 13:56:34 -0000
@@ -176,6 +176,8 @@ static int rand_type = TYPE_3;
 static int rand_deg = DEG_3;
 static int rand_sep = SEP_3;
 
+static int use_arc4random;
+
 _THREAD_PRIVATE_MUTEX(random);
 static long random_l(void);
 
@@ -201,6 +203,7 @@ srandom_l(unsigned int x)
        int32_t test;
        div_t val;
 
+       use_arc4random = 0;
        if (rand_type == TYPE_0)
                state[0] = x;
        else {
@@ -254,17 +257,7 @@ srandomdev(void)
        size_t len;
 
        LOCK();
-       if (rand_type == TYPE_0)
-               len = sizeof(state[0]);
-       else
-               len = rand_deg * sizeof(state[0]);
-
-       arc4random_buf(state, len);
-
-       if (rand_type != TYPE_0) {
-               fptr = &state[rand_sep];
-               rptr = &state[0];
-       }
+       use_arc4random = 1;
        UNLOCK();
 }
 
@@ -411,6 +404,9 @@ static long
 random_l(void)
 {
        int32_t i;
+
+       if (use_arc4random)
+               return arc4random() & 0x7fffffff;
 
        if (rand_type == TYPE_0)
                i = state[0] = (state[0] * 1103515245 + 12345) & 0x7fffffff;