From c18627f7c2d103a5dd232cf79b8202ade5361848 Mon Sep 17 00:00:00 2001
From: Henry de Valence <hdevalence@hdevalence.ca>
Date: Thu, 4 May 2017 00:02:29 -0700
Subject: [PATCH] Generalize k_fold_scalar_mult

---
 src/curve.rs | 20 ++++++++++++--------
 src/decaf.rs |  9 +++++----
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/src/curve.rs b/src/curve.rs
index ca3e4a1..78ff254 100644
--- a/src/curve.rs
+++ b/src/curve.rs
@@ -1066,12 +1066,15 @@ pub mod vartime {
     ///
     /// A vector of `Scalar`s and a vector of `ExtendedPoints`.  It is an
     /// error to call this function with two vectors of different lengths.
-    pub fn k_fold_scalar_mult(scalars: &Vec<Scalar>,
-                            points: &Vec<ExtendedPoint>) -> ExtendedPoint {
-        assert_eq!(scalars.len(), points.len());
+    pub fn k_fold_scalar_mult<'a,'b,I,J>(scalars: I, points: J) -> ExtendedPoint
+        where I: IntoIterator<Item=&'a Scalar>, J: IntoIterator<Item=&'b ExtendedPoint>
+    {
+        //assert_eq!(scalars.len(), points.len());
 
-        let nafs: Vec<_> = scalars.iter().map(|c| c.non_adjacent_form()).collect();
-        let odd_multiples: Vec<_> = points.iter().map(|P| OddMultiples::create(&P)).collect();
+        let nafs: Vec<_> = scalars.into_iter()
+            .map(|c| c.non_adjacent_form()).collect();
+        let odd_multiples: Vec<_> = points.into_iter()
+            .map(|P| OddMultiples::create(P)).collect();
 
         let mut r = ProjectivePoint::identity();
 
@@ -1471,9 +1474,10 @@ mod test {
         #[test]
         fn k_fold_scalar_mult_vs_ed25519py() {
             let A = A_TIMES_BASEPOINT.decompress().unwrap();
-            let points = vec![A,constants::ED25519_BASEPOINT];
-            let scalars = vec![A_SCALAR, B_SCALAR];
-            let result = vartime::k_fold_scalar_mult(&scalars, &points);
+            let result = vartime::k_fold_scalar_mult(
+                &[A_SCALAR, B_SCALAR],
+                &[A, constants::ED25519_BASEPOINT]
+            );
             assert_eq!(result.compress_edwards(), DOUBLE_SCALAR_MULT_RESULT);
         }
     }
diff --git a/src/decaf.rs b/src/decaf.rs
index 9d1a830..4fba23f 100644
--- a/src/decaf.rs
+++ b/src/decaf.rs
@@ -318,10 +318,11 @@ pub mod vartime {
     ///
     /// A vector of `Scalar`s and a vector of `ExtendedPoints`.  It is an
     /// error to call this function with two vectors of different lengths.
-    pub fn k_fold_scalar_mult(scalars: &Vec<Scalar>,
-                              points: &Vec<DecafPoint>) -> DecafPoint {
-        let extended_points: Vec<ExtendedPoint> = points.iter().map(|P| P.0).collect();
-        DecafPoint(curve::vartime::k_fold_scalar_mult(scalars, &extended_points))
+    pub fn k_fold_scalar_mult<'a,'b,I,J>(scalars: I, points: J) -> DecafPoint
+        where I: IntoIterator<Item=&'a Scalar>, J: IntoIterator<Item=&'b DecafPoint>
+    {
+        let extended_points = points.into_iter().map(|P| &P.0);
+        DecafPoint(curve::vartime::k_fold_scalar_mult(scalars, extended_points))
     }
 }