rand: ensure that rand_between() can reach max value

[fio.git] / lib / rand.h

diff --git a/lib/rand.h b/lib/rand.h
index 8832c73a7687412241dbe3e9bddbdad6ba5c2b2b..3554f6985e93ff02eacfb364054a5594007e88e5 100644 (file)
--- a/lib/rand.h
+++ b/lib/rand.h
@@ -117,14 +117,33 @@ static inline double __rand_0_1(struct frand_state *state)
 /*
  * Generate a random value between 'start' and 'end', both inclusive
  */
-static inline int rand32_between(struct frand_state *state, int start, int end)
+static inline uint32_t rand32_upto(struct frand_state *state, uint32_t end)
 {
        uint32_t r;
 
        assert(!state->use64);
 
        r = __rand32(&state->state32);
-       return start + (int) ((double)end * (r / (FRAND32_MAX + 1.0)));
+       return (int) ((double)end * (r / (FRAND32_MAX + 1.0)));
+}
+
+static inline uint64_t rand64_upto(struct frand_state *state, uint64_t end)
+{
+       uint64_t r;
+
+       assert(state->use64);
+
+       r = __rand64(&state->state64);
+       return (uint64_t) ((double)end * (r / (FRAND64_MAX + 1.0)));
+}
+
+static inline uint64_t rand_between(struct frand_state *state, uint64_t start,
+                                   uint64_t end)
+{
+       if (state->use64)
+               return start + rand64_upto(state, 1 + end - start);
+       else
+               return start + rand32_upto(state, 1 + end - start);
 }
 
 extern void init_rand(struct frand_state *, bool);