add to_bits_be

r1cs-std/src/bits/mod.rs

@@ -25,13 +25,27 @@ pub trait ToBitsGadget {
     /// This is the correct default for 99% of use cases.
     fn to_bits_le(&self) -> Result<Vec<Boolean<F>>, SynthesisError>;
 
-    /// Outputs a possibly non-unique bit-wise representation of `self`.
+    /// Outputs a possibly non-unique little-endian bit-wise representation of `self`.
     ///
     /// If you're not absolutely certain that your usecase can get away with a
     /// non-canonical representation, please use `self.to_bits()` instead.
     fn to_non_unique_bits_le(&self) -> Result<Vec<Boolean<F>>, SynthesisError> {
         self.to_bits_le()
     }
+
+    /// Outputs the canonical big-endian bit-wise representation of `self`.
+    fn to_bits_be(&self) -> Result<Vec<Boolean<F>>, SynthesisError> {
+        let mut res = self.to_bits_le()?;
+        res.reverse();
+        Ok(res)
+    }
+
+    /// Outputs a possibly non-unique big-endian bit-wise representation of `self`.
+    fn to_non_unique_bits_be(&self) -> Result<Vec<Boolean<F>>, SynthesisError> {
+        let mut res = self.to_non_unique_bits_le()?;
+        res.reverse();
+        Ok(res)
+    }
 }
 
 impl<F: Field> ToBitsGadget<F> for Boolean<F> {