Consolidate code for choosing a window size for fixed width window

exponentiation algorithms.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/math/numbertheory/pow_mod.h b/src/math/numbertheory/pow_mod.h
index 6952dcd1b..7b92f0ec4 100644
--- a/src/math/numbertheory/pow_mod.h
+++ b/src/math/numbertheory/pow_mod.h
@@ -31,6 +31,7 @@ class BOTAN_DLL Modular_Exponentiator
 class BOTAN_DLL Power_Mod
    {
    public:
+
       enum Usage_Hints {
          NO_HINTS        = 0x0000,
 
@@ -44,6 +45,12 @@ class BOTAN_DLL Power_Mod
          EXP_IS_LARGE    = 0x0400
       };
 
+      /*
+      * Try to choose a good window size
+      */
+      static u32bit window_bits(u32bit exp_bits, u32bit base_bits,
+                                Power_Mod::Usage_Hints hints);
+
       void set_modulus(const BigInt&, Usage_Hints = NO_HINTS) const;
       void set_base(const BigInt&) const;
       void set_exponent(const BigInt&) const;