1 files changed, 87 insertions, 0 deletions
diff --git a/src/entropy/entropy_acc.cpp b/src/entropy/entropy_acc.cpp
new file mode 100644
index 000000000..9dc0f1405
--- /dev/null
+++ b/src/entropy/entropy_acc.cpp
@@ -0,0 +1,87 @@
+/**
+* Entropy Accumulator
+* (C) 1999-2009 Jack Lloyd
+*/
+
+#include <botan/entropy_src.h>
+
+namespace Botan {
+
+void Entropy_Accumulator::reset_goal(u32bit entropy_goal)
+   {
+   goal_bits = entropy_goal;
+   collected_bits = 0;
+
+   /*
+   * The buffer is large enough to hold 2*goal_bits of entropy,
+   * or 128 bits, whichever is larger
+   */
+   entropy_buf.create(std::max<u32bit>(goal_bits / 4, 16));
+   io_buffer.destroy();
+   }
+
+MemoryRegion<byte>& Entropy_Accumulator::get_io_buffer(u32bit size)
+   {
+   io_buffer.create(size);
+   return io_buffer;
+   }
+
+u32bit Entropy_Accumulator::desired_remaining_bits() const
+   {
+   if(collected_bits >= goal_bits)
+      return 0;
+   return (goal_bits - collected_bits);
+   }
+
+bool Entropy_Accumulator::polling_goal_achieved() const
+   {
+   return (collected_bits >= goal_bits);
+   }
+
+void Entropy_Accumulator::add(const void* in_void,
+                              u32bit length,
+                              double entropy_bits_per_byte)
+   {
+   if(length == 0)
+      return;
+
+   entropy_bits_per_byte = std::max(0.0, std::min(entropy_bits_per_byte, 8.0));
+
+   const byte* in = static_cast<const byte*>(in_void);
+
+   u32bit buf_i = 0; // write index into entropy_buf
+   u32bit bytes_collected = 0;
+
+   byte last = 0;
+   byte count = 0;
+
+   for(u32bit i = 0; i != length; ++i)
+      {
+      if(in[i] != last) // run length encode the input
+         {
+         entropy_buf[buf_i] ^= last;
+         buf_i = (buf_i + 1) % entropy_buf.size();
+
+         if(count > 1)
+            {
+            entropy_buf[buf_i] ^= count;
+            buf_i = (buf_i + 1) % entropy_buf.size();
+            }
+
+         ++bytes_collected;
+
+         last = in[i];
+         count = 1;
+         }
+      else
+         ++count;
+      }
+
+   entropy_buf[0] ^= last;
+   entropy_buf[1] ^= count;
+
+   collected_bits += static_cast<u32bit>(entropy_bits_per_byte * bytes_collected);
+   collected_bits = std::min(collected_bits, 8 * entropy_buf.size());
+   }
+
+}