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, 7 insertions, 6 deletions

diff --git a/src/block/lubyrack/lubyrack.cpp b/src/block/lubyrack/lubyrack.cpp
index aa33c6bc4..335570973 100644
--- a/src/block/lubyrack/lubyrack.cpp
+++ b/src/block/lubyrack/lubyrack.cpp
@@ -42,8 +42,8 @@ void LubyRackoff::encrypt_n(const byte in[], byte out[], size_t blocks) const
       hash->final(buffer);
       xor_buf(out, buffer, len);
 
-      in += block_size();
-      out += block_size();
+      in += 2 * len;
+      out += 2 * len;
       }
    }
 
@@ -79,8 +79,8 @@ void LubyRackoff::decrypt_n(const byte in[], byte out[], size_t blocks) const
       hash->final(buffer);
       xor_buf(out + len, buffer, len);
 
-      in += block_size();
-      out += block_size();
+      in += 2 * len;
+      out += 2 * len;
       }
    }
 
@@ -123,8 +123,7 @@ std::string LubyRackoff::name() const
 * Luby-Rackoff Constructor
 */
 LubyRackoff::LubyRackoff(HashFunction* h) :
-   BlockCipher(2 * (h ? h->output_length(): 0),
-               2, 32, 2),
+   BlockCipher(2, 32, 2),
    hash(h)
    {
    }
diff --git a/src/block/lubyrack/lubyrack.h b/src/block/lubyrack/lubyrack.h
index 4567215e1..0c267683a 100644
--- a/src/block/lubyrack/lubyrack.h
+++ b/src/block/lubyrack/lubyrack.h
@@ -22,6 +22,8 @@ class BOTAN_DLL LubyRackoff : public BlockCipher
       void encrypt_n(const byte in[], byte out[], size_t blocks) const;
       void decrypt_n(const byte in[], byte out[], size_t blocks) const;
 
+      size_t block_size() const { return 2 * hash->output_length(); }
+
       void clear();
       std::string name() const;
       BlockCipher* clone() const;