From c6dc9d318d37629d7178615a9bb2b35f20998dcb Mon Sep 17 00:00:00 2001
From: Henry & Isis <henry+isis@en.ciph.re>
Date: Wed, 3 May 2017 19:06:41 -0700
Subject: [PATCH] Add a helper function to construct a Scalar from a u64

---
 src/scalar.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/scalar.rs b/src/scalar.rs
index 067f780..73b30f1 100644
--- a/src/scalar.rs
+++ b/src/scalar.rs
@@ -261,6 +261,15 @@ impl Scalar {
                  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ])
     }
 
+    /// Construct a scalar from the given `u64`.
+    pub fn from_u64(x: u64) -> Scalar {
+        let mut s = Scalar::zero();
+        for i in 0..8 {
+            s[i] = (x >> (i*8)) as u8;
+        }
+        s
+    }
+
     /// Compute the multiplicative inverse of this scalar.
     pub fn invert(&self) -> Scalar {
         self.unpack().invert().pack()
@@ -728,6 +737,20 @@ mod test {
         }
     }
 
+    #[test]
+    fn from_unsigned() {
+        let val = 0xdeadbeefdeadbeef;
+        let s = Scalar::from_u64(val);
+        assert_eq!(s[7], 0xde);
+        assert_eq!(s[6], 0xad);
+        assert_eq!(s[5], 0xbe);
+        assert_eq!(s[4], 0xef);
+        assert_eq!(s[3], 0xde);
+        assert_eq!(s[2], 0xad);
+        assert_eq!(s[1], 0xbe);
+        assert_eq!(s[0], 0xef);
+    }
+
     #[test]
     fn scalar_multiply_by_one() {
         let one = Scalar::one();