Add function comment [ci skip]

1 files changed, 6 insertions, 0 deletions

diff --git a/src/lib/math/numbertheory/reducer.h b/src/lib/math/numbertheory/reducer.h
index 65d9956f2..b1c2c87a9 100644
--- a/src/lib/math/numbertheory/reducer.h
+++ b/src/lib/math/numbertheory/reducer.h
@@ -47,6 +47,12 @@ class BOTAN_PUBLIC_API(2,0) Modular_Reducer
       BigInt cube(const BigInt& x) const
          { return multiply(x, this->square(x)); }
 
+      /**
+      * Low level reduction function. Mostly for internal use.
+      * Sometimes useful for performance by reducing temporaries
+      * Reduce x mod p and place the output in out. ** X and out must not reference each other **
+      * ws is a temporary workspace.
+      */
       void reduce(BigInt& out, const BigInt& x, secure_vector<word>& ws) const;
 
       bool initialized() const { return (m_mod_words != 0); }