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/*************************************************
* Entropy_Estimator Header File *
* (C) 2008 Jack Lloyd *
*************************************************/
#ifndef BOTAN_ENTROPY_ESTIMATOR_H__
#define BOTAN_ENTROPY_ESTIMATOR_H__
#include <botan/types.h>
#include <algorithm>
namespace Botan {
/**
Naive Entropy Estimation using first, second, and third order deltas
@todo It would be nice to extend this to test using zlib or bzip2 if
those modules are compiled in to the library
*/
class BOTAN_DLL Entropy_Estimator
{
public:
Entropy_Estimator()
{ last = last_delta = last_delta2 = 0; estimate = 0; }
/**
Return the current estimate
*/
u32bit value() const { return estimate; }
/**
Set an upper bound on the estimate so far
*/
void set_upper_bound(u32bit upper_limit)
{ estimate = std::min(estimate, upper_limit); }
/**
Add more entropy data to the current estimation
*/
void update(const byte buffer[], u32bit length, u32bit upper_limit = 0);
private:
u32bit estimate;
byte last, last_delta, last_delta2;
};
}
#endif
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