Add a new subclass for BlockCipher BlockCipher_Fixed_Block_Size, which

sets the block size statically and also creates an enum with the
size. Use the enum instead of calling block_size() where possible,
since that uses two virtual function calls per block which is quite
unfortunate. The real advantages here as compared to the previous
version which kept the block size as a per-object u32bit:

 - The compiler can inline the constant as an immediate operand
   (previously it would load the value via an indirection on this)

 - Removes 32 bits per object overhead (except in cases with actually
   variable block sizes, which are very few and rarely used)

2 files changed, 6 insertions, 6 deletions

diff --git a/src/block/rc6/rc6.cpp b/src/block/rc6/rc6.cpp
index df87acbb1..53ca5a7a2 100644
--- a/src/block/rc6/rc6.cpp
+++ b/src/block/rc6/rc6.cpp
@@ -55,8 +55,8 @@ void RC6::encrypt_n(const byte in[], byte out[], size_t blocks) const
 
       store_le(out, A, B, C, D);
 
-      in += block_size();
-      out += block_size();
+      in += BLOCK_SIZE;
+      out += BLOCK_SIZE;
       }
    }
 
@@ -103,8 +103,8 @@ void RC6::decrypt_n(const byte in[], byte out[], size_t blocks) const
 
       store_le(out, A, B, C, D);
 
-      in += block_size();
-      out += block_size();
+      in += BLOCK_SIZE;
+      out += BLOCK_SIZE;
       }
    }
 
diff --git a/src/block/rc6/rc6.h b/src/block/rc6/rc6.h
index 307834a8c..8446138e0 100644
--- a/src/block/rc6/rc6.h
+++ b/src/block/rc6/rc6.h
@@ -15,7 +15,7 @@ namespace Botan {
 /**
 * RC6, Ron Rivest's AES candidate
 */
-class BOTAN_DLL RC6 : public BlockCipher
+class BOTAN_DLL RC6 : public BlockCipher_Fixed_Block_Size<16>
    {
    public:
       void encrypt_n(const byte in[], byte out[], size_t blocks) const;
@@ -25,7 +25,7 @@ class BOTAN_DLL RC6 : public BlockCipher
       std::string name() const { return "RC6"; }
       BlockCipher* clone() const { return new RC6; }
 
-      RC6() : BlockCipher(16, 1, 32), S(44) {}
+      RC6() : BlockCipher_Fixed_Block_Size(1, 32), S(44) {}
    private:
       void key_schedule(const byte[], size_t);