From 08ac5a906859018aac377ac077a1f2fd1b934d83 Mon Sep 17 00:00:00 2001
From: Henry de Valence <hdevalence@hdevalence.ca>
Date: Sun, 12 Mar 2017 23:18:35 -0700
Subject: [PATCH] Add radix51 impl of from_bytes

---
 src/field.rs | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/src/field.rs b/src/field.rs
index 22a9b97..a4e3832 100644
--- a/src/field.rs
+++ b/src/field.rs
@@ -75,21 +75,6 @@ pub fn mul64(a: &[u64;5], b: &[u64;5]) -> [u64;5] {
     [c0,c1,c2,c3,c4]
 }
 
-fn from_bytes_64(bytes: &[u8;32]) -> [u64; 5] {
-    let low_51_bit_mask = (1u64 << 51) - 1;
-    // load bits [  0, 64), no shift
-    [  load8(&bytes[ 0..])        & low_51_bit_mask
-    // load bits [ 48,112), shift to [ 51,112)
-    , (load8(&bytes[ 6..]) >>  3) & low_51_bit_mask
-    // load bits [ 96,160), shift to [102,160)
-    , (load8(&bytes[12..]) >>  6) & low_51_bit_mask
-    // load bits [152,216), shift to [153,216)
-    , (load8(&bytes[19..]) >>  1) & low_51_bit_mask
-    // load bits [192,256), shift to [204,112)
-    , (load8(&bytes[24..]) >> 12) & low_51_bit_mask
-    ]
-}
-
 fn to_bytes_64(limbs: &[u64;5]) -> [u8;32] {
     let mut s = [0u8;32];
     s[ 0] =   limbs[0]        as u8;
@@ -507,6 +492,22 @@ impl FieldElement {
 
         FieldElement::reduce(&h)
     }
+    #[cfg(feature="radix_51")]
+    pub fn from_bytes(bytes: &[u8;32]) -> FieldElement {
+        let low_51_bit_mask = (1u64 << 51) - 1;
+        FieldElement(
+        // load bits [  0, 64), no shift
+        [  load8(&bytes[ 0..])        & low_51_bit_mask
+        // load bits [ 48,112), shift to [ 51,112)
+        , (load8(&bytes[ 6..]) >>  3) & low_51_bit_mask
+        // load bits [ 96,160), shift to [102,160)
+        , (load8(&bytes[12..]) >>  6) & low_51_bit_mask
+        // load bits [152,216), shift to [153,216)
+        , (load8(&bytes[19..]) >>  1) & low_51_bit_mask
+        // load bits [192,256), shift to [204,112)
+        , (load8(&bytes[24..]) >> 12) & low_51_bit_mask
+        ])
+    }
 
     /// Marshal this FieldElement into a 32-byte array.
     ///