Make Entropy_Accumulator a pure virtual to allow other accumulation

techniques, with the one using BufferedComputation being the new
subclass with the charming name Entropy_Accumulator_BufferedComputation.

3 files changed, 28 insertions, 7 deletions

diff --git a/src/entropy/entropy_src.h b/src/entropy/entropy_src.h
index 96ffcad0b..c294ca6ac 100644
--- a/src/entropy/entropy_src.h
+++ b/src/entropy/entropy_src.h
@@ -18,8 +18,10 @@ namespace Botan {
 class Entropy_Accumulator
    {
    public:
-      Entropy_Accumulator(BufferedComputation& sink, u32bit goal) :
-         entropy_sink(sink), entropy_goal(goal), collected_bits(0) {}
+      Entropy_Accumulator(u32bit goal) :
+         entropy_goal(goal), collected_bits(0) {}
+
+      virtual ~Entropy_Accumulator() {}
 
       /**
       @return cached I/O buffer for repeated polls
@@ -34,12 +36,14 @@ class Entropy_Accumulator
 
       u32bit desired_remaining_bits() const
          {
-         return (collected_bits >= entropy_goal) ? 0 : (entropy_goal - collected_bits);
+         if(collected_bits >= entropy_goal)
+            return 0;
+         return (entropy_goal - collected_bits);
          }
 
       void add(const void* bytes, u32bit length, double entropy_bits_per_byte)
          {
-         entropy_sink.update(reinterpret_cast<const byte*>(bytes), length);
+         add_bytes(bytes, length);
          collected_bits += std::min<u32bit>(8, entropy_bits_per_byte) * length;
          }
 
@@ -49,11 +53,28 @@ class Entropy_Accumulator
          add(&v, sizeof(T), entropy_bits_per_byte);
          }
    private:
-      BufferedComputation& entropy_sink;
+      virtual void add_bytes(const void* bytes, u32bit length) = 0;
+
       SecureVector<byte> io_buffer;
       u32bit entropy_goal, collected_bits;
    };
 
+class Entropy_Accumulator_BufferedComputation : public Entropy_Accumulator
+   {
+   public:
+      Entropy_Accumulator_BufferedComputation(BufferedComputation& sink,
+                                              u32bit goal) :
+         Entropy_Accumulator(goal), entropy_sink(sink) {}
+
+   private:
+      virtual void add_bytes(const void* bytes, u32bit length)
+         {
+         entropy_sink.update(reinterpret_cast<const byte*>(bytes), length);
+         }
+
+      BufferedComputation& entropy_sink;
+   };
+
 /**
 * Abstract interface to a source of (hopefully unpredictable) system entropy
 */
diff --git a/src/rng/hmac_rng/hmac_rng.cpp b/src/rng/hmac_rng/hmac_rng.cpp
index ffdfdc60d..ede2b5a08 100644
--- a/src/rng/hmac_rng/hmac_rng.cpp
+++ b/src/rng/hmac_rng/hmac_rng.cpp
@@ -69,7 +69,7 @@ void HMAC_RNG::reseed_with_input(u32bit poll_bits,
    feedback of the current PRK value, into the extractor function.
    */
 
-   Entropy_Accumulator accum(*extractor, poll_bits);
+   Entropy_Accumulator_BufferedComputation accum(*extractor, poll_bits);
 
    for(u32bit i = 0; i < entropy_sources.size(); ++i)
       {
diff --git a/src/rng/randpool/randpool.cpp b/src/rng/randpool/randpool.cpp
index 41a8ca23a..98b088808 100644
--- a/src/rng/randpool/randpool.cpp
+++ b/src/rng/randpool/randpool.cpp
@@ -101,7 +101,7 @@ void Randpool::mix_pool()
 */
 void Randpool::reseed(u32bit poll_bits)
    {
-   Entropy_Accumulator accum(*mac, poll_bits);
+   Entropy_Accumulator_BufferedComputation accum(*mac, poll_bits);
 
    for(u32bit i = 0; i != entropy_sources.size(); ++i)
       {