trunhash.h

00001 #ifndef CRYPTOPP_TRUNHASH_H
00002 #define CRYPTOPP_TRUNHASH_H
00003 
00004 #include "cryptlib.h"
00005 
00006 NAMESPACE_BEGIN(CryptoPP)
00007 
00008 class NullHash : public HashTransformation
00009 {
00010 public:
00011     void Update(const byte *input, size_t length) {}
00012     unsigned int DigestSize() const {return 0;}
00013     void TruncatedFinal(byte *digest, size_t digestSize) {}
00014     bool TruncatedVerify(const byte *digest, size_t digestLength) {return true;}
00015 };
00016 
00017 //! construct new HashModule with smaller DigestSize() from existing one
00018 template <class T>
00019 class TruncatedHashTemplate : public HashTransformation
00020 {
00021 public:
00022     TruncatedHashTemplate(T hm, unsigned int digestSize)
00023         : m_hm(hm), m_digestSize(digestSize) {}
00024     TruncatedHashTemplate(const byte *key, size_t keyLength, unsigned int digestSize)
00025         : m_hm(key, keyLength), m_digestSize(digestSize) {}
00026     TruncatedHashTemplate(size_t digestSize)
00027         : m_digestSize(digestSize) {}
00028 
00029     void Restart()
00030         {m_hm.Restart();}
00031     void Update(const byte *input, size_t length)
00032         {m_hm.Update(input, length);}
00033     unsigned int DigestSize() const {return m_digestSize;}
00034     void TruncatedFinal(byte *digest, size_t digestSize)
00035         {m_hm.TruncatedFinal(digest, digestSize);}
00036     bool TruncatedVerify(const byte *digest, size_t digestLength)
00037         {return m_hm.TruncatedVerify(digest, digestLength);}
00038 
00039 private:
00040     T m_hm;
00041     unsigned int m_digestSize;
00042 };
00043 
00044 typedef TruncatedHashTemplate<HashTransformation &> TruncatedHashModule;
00045 
00046 NAMESPACE_END
00047 
00048 #endif

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