Speedup verify random fills by 10-15x

Move the pseudo-random helper into lib/rand.c and use that
from the verify populate as well.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/lib/rand.c b/lib/rand.c
index cecc4c2..839a6a9 100644
--- a/lib/rand.c
+++ b/lib/rand.c
@@ -34,6 +34,7 @@
 */
 
 #include "rand.h"
+#include "../hash.h"
 
 struct frand_state __fio_rand_state;
 
@@ -57,3 +58,19 @@
 	__rand(state);
 	__rand(state);
 }
+
+void fill_random_buf(void *buf, unsigned int len)
+{
+	unsigned long r = __rand(&__fio_rand_state);
+	long *ptr = buf;
+
+	if (sizeof(int) != sizeof(*ptr))
+		r *= (unsigned long) __rand(&__fio_rand_state);
+
+	while ((void *) ptr - buf < len) {
+		*ptr = r;
+		ptr++;
+		r *= GOLDEN_RATIO_PRIME;
+		r >>= 3;
+	}
+}