trunhash.h

#ifndef CRYPTOPP_TRUNHASH_H
#define CRYPTOPP_TRUNHASH_H

#include "cryptlib.h"

NAMESPACE_BEGIN(CryptoPP)

class NullHash : public HashTransformation
{
public:
        void Update(const byte *input, size_t length) {}
        unsigned int DigestSize() const {return 0;}
        void TruncatedFinal(byte *digest, size_t digestSize) {}
        bool TruncatedVerify(const byte *digest, size_t digestLength) {return true;}
};

//! construct new HashModule with smaller DigestSize() from existing one
template <class T>
class TruncatedHashTemplate : public HashTransformation
{
public:
        TruncatedHashTemplate(T hm, unsigned int digestSize)
                : m_hm(hm), m_digestSize(digestSize) {}
        TruncatedHashTemplate(const byte *key, size_t keyLength, unsigned int digestSize)
                : m_hm(key, keyLength), m_digestSize(digestSize) {}
        TruncatedHashTemplate(size_t digestSize)
                : m_digestSize(digestSize) {}

        void Restart()
                {m_hm.Restart();}
        void Update(const byte *input, size_t length)
                {m_hm.Update(input, length);}
        unsigned int DigestSize() const {return m_digestSize;}
        void TruncatedFinal(byte *digest, size_t digestSize)
                {m_hm.TruncatedFinal(digest, digestSize);}
        bool TruncatedVerify(const byte *digest, size_t digestLength)
                {return m_hm.TruncatedVerify(digest, digestLength);}

private:
        T m_hm;
        unsigned int m_digestSize;
};

typedef TruncatedHashTemplate<HashTransformation &> TruncatedHashModule;

NAMESPACE_END

#endif

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