Fix a bug in Barrett reduction

-x*n % n would reduce to n instead of zero.

Also some small optimizations and cleanups.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/tests/test_bigint.cpp b/src/tests/test_bigint.cpp
index b62fa307d..8074a4f3b 100644
--- a/src/tests/test_bigint.cpp
+++ b/src/tests/test_bigint.cpp
@@ -9,6 +9,7 @@
 #if defined(BOTAN_HAS_NUMBERTHEORY)
    #include <botan/bigint.h>
    #include <botan/numthry.h>
+   #include <botan/reducer.h>
    #include <botan/pow_mod.h>
    #include <botan/parsing.h>
    #include "test_rng.h"
@@ -398,6 +399,9 @@ class BigInt_Mod_Test final : public Text_Based_Test
          e %= b;
          result.test_eq("a %= b", e, c);
 
+         const Botan::Modular_Reducer mod_b(b);
+         result.test_eq("Barrett", mod_b.reduce(a), c);
+
          // if b fits into a Botan::word test %= operator for words
          if(b.bytes() <= sizeof(Botan::word))
             {