Add connection_verbose setting to log IO events (#774)

src/util.rs

@@ -0,0 +1,35 @@
+// xor-shift
+pub(crate) fn fast_random() -> u64 {
+    use std::cell::Cell;
+    use std::collections::hash_map::RandomState;
+    use std::hash::{BuildHasher, Hasher};
+    use std::num::Wrapping;
+
+    thread_local! {
+        static RNG: Cell<Wrapping<u64>> = Cell::new(Wrapping(seed()));
+    }
+
+    fn seed() -> u64 {
+        let seed = RandomState::new();
+
+        let mut out = 0;
+        let mut cnt = 0;
+        while out == 0 {
+            cnt += 1;
+            let mut hasher = seed.build_hasher();
+            hasher.write_usize(cnt);
+            out = hasher.finish();
+        }
+        out
+    }
+
+    RNG.with(|rng| {
+        let mut n = rng.get();
+        debug_assert_ne!(n.0, 0);
+        n ^= n >> 12;
+        n ^= n << 25;
+        n ^= n >> 27;
+        rng.set(n);
+        n.0.wrapping_mul(0x2545_f491_4f6c_dd1d)
+    })
+}