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, 10 insertions, 10 deletions

diff --git a/src/block/xtea/xtea.cpp b/src/block/xtea/xtea.cpp
index ba07ba57c..597eedd07 100644
--- a/src/block/xtea/xtea.cpp
+++ b/src/block/xtea/xtea.cpp
@@ -64,8 +64,8 @@ void XTEA::encrypt_n(const byte in[], byte out[], size_t blocks) const
    while(blocks >= 4)
       {
       xtea_encrypt_4(in, out, &(this->EK[0]));
-      in += 4 * block_size();
-      out += 4 * block_size();
+      in += 4 * BLOCK_SIZE;
+      out += 4 * BLOCK_SIZE;
       blocks -= 4;
       }
 
@@ -82,8 +82,8 @@ void XTEA::encrypt_n(const byte in[], byte out[], size_t blocks) const
 
       store_be(out, L, R);
 
-      in += block_size();
-      out += block_size();
+      in += BLOCK_SIZE;
+      out += BLOCK_SIZE;
       }
    }
 
@@ -95,8 +95,8 @@ void XTEA::decrypt_n(const byte in[], byte out[], size_t blocks) const
    while(blocks >= 4)
       {
       xtea_decrypt_4(in, out, &(this->EK[0]));
-      in += 4 * block_size();
-      out += 4 * block_size();
+      in += 4 * BLOCK_SIZE;
+      out += 4 * BLOCK_SIZE;
       blocks -= 4;
       }
 
@@ -113,8 +113,8 @@ void XTEA::decrypt_n(const byte in[], byte out[], size_t blocks) const
 
       store_be(out, L, R);
 
-      in += block_size();
-      out += block_size();
+      in += BLOCK_SIZE;
+      out += BLOCK_SIZE;
       }
    }
 
diff --git a/src/block/xtea/xtea.h b/src/block/xtea/xtea.h
index c870f588a..539725be8 100644
--- a/src/block/xtea/xtea.h
+++ b/src/block/xtea/xtea.h
@@ -15,7 +15,7 @@ namespace Botan {
 /**
 * XTEA
 */
-class BOTAN_DLL XTEA : public BlockCipher
+class BOTAN_DLL XTEA : 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 XTEA : public BlockCipher
       std::string name() const { return "XTEA"; }
       BlockCipher* clone() const { return new XTEA; }
 
-      XTEA() : BlockCipher(8, 16), EK(64) {}
+      XTEA() : BlockCipher_Fixed_Block_Size(16), EK(64) {}
    protected:
       /**
       * @return const reference to the key schedule