Add muln() to PrimeFieldRepr along with tests for muln/divn.

src/tests/repr.rs

@@ -2,20 +2,64 @@ use rand::{SeedableRng, XorShiftRng};
 use ::{PrimeFieldRepr};
 
 pub fn random_repr_tests<R: PrimeFieldRepr>() {
-	random_encoding_tests::<R>();
+    random_encoding_tests::<R>();
+    random_muln_tests::<R>();
+    random_divn_tests::<R>();
 }
 
 fn random_encoding_tests<R: PrimeFieldRepr>() {
-	let mut rng = XorShiftRng::from_seed([0x5dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
+    let mut rng = XorShiftRng::from_seed([0x5dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
 
-	for _ in 0..1000 {
-		let r = R::rand(&mut rng);
-		let mut rdecoded = R::default();
+    for _ in 0..1000 {
+        let r = R::rand(&mut rng);
+        let mut rdecoded = R::default();
 
-		let mut v: Vec<u8> = vec![];
-		r.write_be(&mut v).unwrap();
-		rdecoded.read_be(&v[0..]).unwrap();
+        let mut v: Vec<u8> = vec![];
+        r.write_be(&mut v).unwrap();
+        rdecoded.read_be(&v[0..]).unwrap();
 
-		assert_eq!(r, rdecoded);
-	}
+        assert_eq!(r, rdecoded);
+    }
+}
+
+fn random_muln_tests<R: PrimeFieldRepr>() {
+    let mut rng = XorShiftRng::from_seed([0x5dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
+
+    for _ in 0..100 {
+        let r = R::rand(&mut rng);
+
+        for shift in 0..(r.num_bits()+1) {
+            let mut r1 = r;
+            let mut r2 = r;
+
+            for _ in 0..shift {
+                r1.mul2();
+            }
+
+            r2.muln(shift);
+
+            assert_eq!(r1, r2);
+        }
+    }
+}
+
+fn random_divn_tests<R: PrimeFieldRepr>() {
+    let mut rng = XorShiftRng::from_seed([0x5dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
+
+    for _ in 0..100 {
+        let r = R::rand(&mut rng);
+
+        for shift in 0..(r.num_bits()+1) {
+            let mut r1 = r;
+            let mut r2 = r;
+
+            for _ in 0..shift {
+                r1.div2();
+            }
+
+            r2.divn(shift);
+
+            assert_eq!(r1, r2);
+        }
+    }
 }