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2633. [bug] Handle 15 bit rand() functions. [RT #19783]

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This commit is contained in:
Mark Andrews
2009-07-16 05:52:46 +00:00
parent 4347f7ac12
commit 2792e226c7
2 changed files with 18 additions and 7 deletions
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23
lib/isc/random.c
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@@ -15,7 +15,7 @@
* PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id: random.c,v 1.27 2009/07/01 23:47:36 tbox Exp $ */
/* $Id: random.c,v 1.28 2009/07/16 05:52:46 marka Exp $ */
/*! \file */
@@ -84,7 +84,16 @@ isc_random_get(isc_uint32_t *val)
* rand()'s lower bits are not random.
* rand()'s upper bit is zero.
*/
#if RAND_MAX >= 0xfffff
/* We have at least 20 bits. Use lower 16 excluding lower most 4 */
*val = ((rand() >> 4) & 0xffff) | ((rand() << 12) & 0xffff0000);
#elif RAND_MAX >= 0x7fff
/* We have at least 15 bits. Use lower 10/11 excluding lower most 4 */
*val = ((rand() >> 4) & 0x000007ff) | ((rand() << 7) & 0x003ff800) |
((rand() << 18) & 0xffc00000);
#else
#error RAND_MAX is too small
#endif
#else
*val = arc4random();
#endif
@@ -92,13 +101,13 @@ isc_random_get(isc_uint32_t *val)
isc_uint32_t
isc_random_jitter(isc_uint32_t max, isc_uint32_t jitter) {
isc_uint32_t rnd;
REQUIRE(jitter < max || (jitter == 0 && max == 0));
if (jitter == 0)
return (max);
else
#ifndef HAVE_ARC4RANDOM
return (max - rand() % jitter);
#else
return (max - arc4random() % jitter);
#endif
isc_random_get(&rnd);
return (max - rnd % jitter);
}