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/skipjack/skipjack.cpp b/src/block/skipjack/skipjack.cpp
index 7f25cc90a..b73972b59 100644
--- a/src/block/skipjack/skipjack.cpp
+++ b/src/block/skipjack/skipjack.cpp
@@ -108,8 +108,8 @@ void Skipjack::encrypt_n(const byte in[], byte out[], size_t blocks) const
 
       store_le(out, W4, W3, W2, W1);
 
-      in += block_size();
-      out += block_size();
+      in += BLOCK_SIZE;
+      out += BLOCK_SIZE;
       }
    }
 
@@ -149,8 +149,8 @@ void Skipjack::decrypt_n(const byte in[], byte out[], size_t blocks) const
 
       store_le(out, W4, W3, W2, W1);
 
-      in += block_size();
-      out += block_size();
+      in += BLOCK_SIZE;
+      out += BLOCK_SIZE;
       }
    }
 
diff --git a/src/block/skipjack/skipjack.h b/src/block/skipjack/skipjack.h
index dff85df6c..73ae28de2 100644
--- a/src/block/skipjack/skipjack.h
+++ b/src/block/skipjack/skipjack.h
@@ -15,7 +15,7 @@ namespace Botan {
 /**
 * Skipjack, a NSA designed cipher used in Fortezza
 */
-class BOTAN_DLL Skipjack : public BlockCipher
+class BOTAN_DLL Skipjack : public BlockCipher_Fixed_Block_Size<8>
    {
    public:
       void encrypt_n(const byte in[], byte out[], size_t blocks) const;
@@ -25,7 +25,7 @@ class BOTAN_DLL Skipjack : public BlockCipher
       std::string name() const { return "Skipjack"; }
       BlockCipher* clone() const { return new Skipjack; }
 
-      Skipjack() : BlockCipher(8, 10), FTAB(2560) {}
+      Skipjack() : BlockCipher_Fixed_Block_Size(10), FTAB(2560) {}
    private:
       void key_schedule(const byte[], size_t);