Add function to get the basepoint from a basepoint table

src/curve.rs

@@ -890,6 +890,13 @@ impl EdwardsBasepointTable {
         }
         table
     }
+
+    /// Get the basepoint for this table as an `ExtendedPoint`.
+    pub fn basepoint(&self) -> ExtendedPoint {
+        // self.0[0][0] has 1*(16^2)^0*B, but as an `AffineNielsPoint`
+        // Add identity to convert to extended.
+        (&ExtendedPoint::identity() + &self.0[0][0]).to_extended()
+    }
 }
 
 impl ExtendedPoint {
@@ -1271,6 +1278,13 @@ mod test {
         assert_eq!(compressed, constants::BASE_CMPRSSD);
     }
 
+    /// Test that `EdwardsBasepointTable::basepoint()` gives the correct basepoint.
+    #[test]
+    fn basepoint_table_basepoint_function_correct() {
+        let bp = constants::ED25519_BASEPOINT_TABLE.basepoint();
+        assert_eq!(bp.compress_edwards(), constants::BASE_CMPRSSD);
+    }
+
     /// Test `impl Add<ExtendedPoint> for ExtendedPoint`
     /// using basepoint + basepoint versus the 2*basepoint constant.
     #[test]

src/decaf.rs

@@ -276,6 +276,11 @@ impl DecafBasepointTable {
     pub fn create(basepoint: &DecafPoint) -> DecafBasepointTable {
         DecafBasepointTable(EdwardsBasepointTable::create(&basepoint.0))
     }
+
+    /// Get the basepoint for this table as a `DecafPoint`.
+    pub fn basepoint(&self) -> DecafPoint {
+        DecafPoint(self.0.basepoint())
+    }
 }
 
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