Remove reseed from SeedableRng

rand_core/src/lib.rs

@@ -137,12 +137,6 @@ pub trait SeedFromRng: Sized {
 /// A random number generator that can be explicitly seeded to produce
 /// the same stream of randomness multiple times.
 pub trait SeedableRng<Seed>: Rng {
-    /// Reseed an RNG with the given seed.
-    /// 
-    /// The type of `Seed` is specified by the implementation (implementation
-    /// for multiple seed types is possible).
-    fn reseed(&mut self, Seed);
-
     /// Create a new RNG with the given seed.
     /// 
     /// The type of `Seed` is specified by the implementation (implementation

rand_core/src/mock.rs

@@ -85,9 +85,6 @@ impl<T> SeedableRng<T> for MockAddRng<T> where
         MockAddRng<T>: Rng,
         T: From<u8>,    // for 1.into()
 {
-    fn reseed(&mut self, seed: T) {
-        self.v = w(seed);
-    }
     fn from_seed(seed: T) -> Self {
         MockAddRng::new(seed, 1.into())
     }

src/prng/chacha.rs

@@ -255,23 +255,20 @@ impl SeedFromRng for ChaChaRng {
 }
 
 impl<'a> SeedableRng<&'a [u32]> for ChaChaRng {
-    fn reseed(&mut self, seed: &'a [u32]) {
-        // reset state
-        self.init(&[0u32; KEY_WORDS]);
-        // set key in place
-        let key = &mut self.state[4 .. 4+KEY_WORDS];
-        for (k, s) in key.iter_mut().zip(seed.iter()) {
-            *k = w(*s);
-        }
-    }
-
     /// Create a ChaCha generator from a seed,
     /// obtained from a variable-length u32 array.
     /// Only up to 8 words are used; if less than 8
     /// words are used, the remaining are set to zero.
     fn from_seed(seed: &'a [u32]) -> ChaChaRng {
         let mut rng = EMPTY;
-        rng.reseed(seed);
+        rng.init(&[0u32; KEY_WORDS]);
+        // set key in place
+        {
+            let key = &mut rng.state[4 .. 4+KEY_WORDS];
+            for (k, s) in key.iter_mut().zip(seed.iter()) {
+                *k = w(*s);
+            }
+        }
         rng
     }
 }
@@ -301,18 +298,6 @@ mod test {
                                 iter(&mut rb).map(|rng| ascii_word_char(rng)).take(100)));
     }
 
-    #[test]
-    fn test_rng_reseed() {
-        let s = iter(&mut ::test::rng()).map(|rng| rng.next_u32()).take(8).collect::<Vec<u32>>();
-        let mut r: ChaChaRng = SeedableRng::from_seed(&s[..]);
-        let string1: String = iter(&mut r).map(|rng| ascii_word_char(rng)).take(100).collect();
-
-        r.reseed(&s);
-
-        let string2: String = iter(&mut r).map(|rng| ascii_word_char(rng)).take(100).collect();
-        assert_eq!(string1, string2);
-    }
-
     #[test]
     fn test_rng_true_values() {
         // Test vectors 1 and 2 from

src/prng/isaac.rs

@@ -306,30 +306,22 @@ impl SeedFromRng for IsaacRng {
 }
 
 impl<'a> SeedableRng<&'a [u32]> for IsaacRng {
-    fn reseed(&mut self, seed: &'a [u32]) {
-        // make the seed into [seed[0], seed[1], ..., seed[seed.len()
-        // - 1], 0, 0, ...], to fill rng.rsl.
-        let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u32));
-
-        for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
-            *rsl_elem = w(seed_elem);
-        }
-        self.cnt = 0;
-        self.a = w(0);
-        self.b = w(0);
-        self.c = w(0);
-
-        self.init(true);
-    }
-
     /// Create an ISAAC random number generator with a seed. This can
     /// be any length, although the maximum number of elements used is
     /// 256 and any more will be silently ignored. A generator
     /// constructed with a given seed will generate the same sequence
     /// of values as all other generators constructed with that seed.
     fn from_seed(seed: &'a [u32]) -> IsaacRng {
         let mut rng = EMPTY;
-        rng.reseed(seed);
+
+        // make the seed into [seed[0], seed[1], ..., seed[seed.len()
+        // - 1], 0, 0, ...], to fill rng.rsl.
+        let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u32));
+
+        for (rsl_elem, seed_elem) in rng.rsl.iter_mut().zip(seed_iter) {
+            *rsl_elem = w(seed_elem);
+        }
+        rng.init(true);
         rng
     }
 }
@@ -364,18 +356,6 @@ mod test {
                                 iter(&mut rb).map(|rng| ascii_word_char(rng)).take(100)));
     }
 
-    #[test]
-    fn test_rng_32_reseed() {
-        let s = iter(&mut ::test::rng()).map(|rng| rng.next_u32()).take(256).collect::<Vec<u32>>();
-        let mut r: IsaacRng = SeedableRng::from_seed(&s[..]);
-        let string1: String = iter(&mut r).map(|rng| ascii_word_char(rng)).take(100).collect();
-
-        r.reseed(&s[..]);
-
-        let string2: String = iter(&mut r).map(|rng| ascii_word_char(rng)).take(100).collect();
-        assert_eq!(string1, string2);
-    }
-
     #[test]
     fn test_rng_32_true_values() {
         let seed: &[_] = &[1, 23, 456, 7890, 12345];

src/prng/isaac64.rs

@@ -292,30 +292,22 @@ impl SeedFromRng for Isaac64Rng {
 }
 
 impl<'a> SeedableRng<&'a [u64]> for Isaac64Rng {
-    fn reseed(&mut self, seed: &'a [u64]) {
-        // make the seed into [seed[0], seed[1], ..., seed[seed.len()
-        // - 1], 0, 0, ...], to fill rng.rsl.
-        let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u64));
-
-        for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
-            *rsl_elem = w(seed_elem);
-        }
-        self.cnt = 0;
-        self.a = w(0);
-        self.b = w(0);
-        self.c = w(0);
-
-        self.init(true);
-    }
-
     /// Create an ISAAC random number generator with a seed. This can
     /// be any length, although the maximum number of elements used is
     /// 256 and any more will be silently ignored. A generator
     /// constructed with a given seed will generate the same sequence
     /// of values as all other generators constructed with that seed.
     fn from_seed(seed: &'a [u64]) -> Isaac64Rng {
         let mut rng = EMPTY_64;
-        rng.reseed(seed);
+
+        // make the seed into [seed[0], seed[1], ..., seed[seed.len()
+        // - 1], 0, 0, ...], to fill rng.rsl.
+        let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u64));
+
+        for (rsl_elem, seed_elem) in rng.rsl.iter_mut().zip(seed_iter) {
+            *rsl_elem = w(seed_elem);
+        }
+        rng.init(true);
         rng
     }
 }
@@ -350,18 +342,6 @@ mod test {
                                 iter(&mut rb).map(|rng| ascii_word_char(rng)).take(100)));
     }
 
-    #[test]
-    fn test_rng_64_reseed() {
-        let s = iter(&mut ::test::rng()).map(|rng| rng.next_u64()).take(256).collect::<Vec<u64>>();
-        let mut r: Isaac64Rng = SeedableRng::from_seed(&s[..]);
-        let string1: String = iter(&mut r).map(|rng| ascii_word_char(rng)).take(100).collect();
-
-        r.reseed(&s[..]);
-
-        let string2: String = iter(&mut r).map(|rng| ascii_word_char(rng)).take(100).collect();
-        assert_eq!(string1, string2);
-    }
-
     #[test]
     fn test_rng_64_true_values() {
         let seed: &[_] = &[1, 23, 456, 7890, 12345];

src/prng/xorshift.rs

@@ -90,17 +90,6 @@ impl Rng for XorShiftRng {
 }
 
 impl SeedableRng<[u32; 4]> for XorShiftRng {
-    /// Reseed an XorShiftRng. This will panic if `seed` is entirely 0.
-    fn reseed(&mut self, seed: [u32; 4]) {
-        assert!(!seed.iter().all(|&x| x == 0),
-                "XorShiftRng.reseed called with an all zero seed.");
-
-        self.x = w(seed[0]);
-        self.y = w(seed[1]);
-        self.z = w(seed[2]);
-        self.w = w(seed[3]);
-    }
-
     /// Create a new XorShiftRng. This will panic if `seed` is entirely 0.
     fn from_seed(seed: [u32; 4]) -> XorShiftRng {
         assert!(!seed.iter().all(|&x| x == 0),