From 7f8734e16184a12434ac92e5bb93dc2d24aebaad Mon Sep 17 00:00:00 2001
From: Dominik Maier <domenukk@gmail.com>
Date: Mon, 9 Nov 2020 21:04:46 +0100
Subject: [PATCH] time-based preseeded rand

---
 src/corpus/mod.rs   |  2 +-
 src/engines/mod.rs  |  2 +-
 src/inputs/bytes.rs |  2 +-
 src/utils.rs        | 31 +++++++++++++++++++++++++------
 4 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/src/corpus/mod.rs b/src/corpus/mod.rs
index 0b0b18b3fc..d15e325d4e 100644
--- a/src/corpus/mod.rs
+++ b/src/corpus/mod.rs
@@ -308,7 +308,7 @@ mod tests {
     #[test]
 
     fn test_queuecorpus() {
-        let rand = Xoshiro256StarRand::new_rr();
+        let rand = Xoshiro256StarRand::preseeded_rr();
         let mut q = QueueCorpus::new(OnDiskCorpus::new(&rand, PathBuf::from("fancy/path")));
         let i = BytesInput::new(vec![0; 4]);
         let t = Testcase::with_filename_rr(i, PathBuf::from("fancyfile"));
diff --git a/src/engines/mod.rs b/src/engines/mod.rs
index 50dff41fe5..2cb06daad8 100644
--- a/src/engines/mod.rs
+++ b/src/engines/mod.rs
@@ -211,7 +211,7 @@ mod tests {
 
     #[test]
     fn test_engine() {
-        let rand = Xoshiro256StarRand::new_rr();
+        let rand = Xoshiro256StarRand::preseeded_rr();
 
         let mut corpus = InMemoryCorpus::<BytesInput, _>::new(&rand);
         let testcase = Testcase::new_rr(BytesInput::new(vec![0; 4]));
diff --git a/src/inputs/bytes.rs b/src/inputs/bytes.rs
index d8a36d1f6c..b096dab1bb 100644
--- a/src/inputs/bytes.rs
+++ b/src/inputs/bytes.rs
@@ -46,7 +46,7 @@ mod tests {
 
     #[test]
     fn test_input() {
-        let mut rand = Xoshiro256StarRand::new();
+        let mut rand = Xoshiro256StarRand::preseeded();
         assert_ne!(rand.next(), rand.next());
         assert!(rand.below(100) < 100);
         assert_eq!(rand.below(1), 0);
diff --git a/src/utils.rs b/src/utils.rs
index 29da8acb96..96068bb76e 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -4,6 +4,8 @@ use std::cell::RefCell;
 use std::debug_assert;
 use std::fmt::Debug;
 use std::rc::Rc;
+use std::time::{SystemTime, UNIX_EPOCH};
+
 use xxhash_rust::xxh3::xxh3_64_with_seed;
 
 /// Ways to get random around here
@@ -106,15 +108,29 @@ impl Rand for Xoshiro256StarRand {
 }
 
 impl Xoshiro256StarRand {
-    pub fn new() -> Self {
+    /// Creates a new Xoshiro rand with the given seed
+    pub fn new(seed: u64) -> Self {
         let mut ret: Xoshiro256StarRand = Default::default();
-        ret.set_seed(0); // TODO: Proper random seed?
+        ret.set_seed(seed); // TODO: Proper random seed?
         ret
     }
 
-    pub fn new_rr() -> Rc<RefCell<Self>> {
-        Rc::new(RefCell::new(Xoshiro256StarRand::new()))
+    /// Creates a new Xoshiro rand with the given seed, wrapped in a Rc<RefCell<T>>.
+    pub fn new_rr(seed: u64) -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(Self::new(seed)))
     }
+
+    /// Creates a rand instance, pre-seeded with the current time in nanoseconds.
+    pub fn preseeded() -> Self {
+        let seed = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_nanos() as u64;
+        Self::new(seed)
+    }
+
+    /// Creates a new rand instance, pre-seeded
+    pub fn preseeded_rr() -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(Self::preseeded()))
+    }
+
 }
 
 /// Get the next higher power of two
@@ -134,7 +150,7 @@ mod tests {
 
     #[test]
     fn test_rand() {
-        let mut rand = Xoshiro256StarRand::new();
+        let mut rand = Xoshiro256StarRand::preseeded();
         assert_ne!(rand.next(), rand.next());
         assert!(rand.below(100) < 100);
         assert_eq!(rand.below(1), 0);
@@ -142,6 +158,7 @@ mod tests {
         assert!(rand.between(11, 20) > 10);
     }
 
+
     use std::cell::RefCell;
     use std::rc::Rc;
     struct HasRandTest<R>
@@ -164,7 +181,7 @@ mod tests {
 
     #[test]
     fn test_has_rand() {
-        let rand = Xoshiro256StarRand::new_rr();
+        let rand = Xoshiro256StarRand::preseeded_rr();
         let has_rand = HasRandTest {
             rand: Rc::clone(&rand),
         };
@@ -173,6 +190,8 @@ mod tests {
         assert_eq!(has_rand.rand_below(1), 0);
     }
 
+
+
     #[test]
     fn test_next_pow2() {
         assert_eq!(next_pow2(0), 0);