Creating and Implementing an Encapsulated Class

• presents the StringCoding class, an encapsulated method of encryption. The benefit of encapsulation is, in effect, that it cuts to the chase: The programmer utilizing our StringCoding class knows nothing about the algorithm used to encrypt strings — and doesn’t really need to know what data was used to encrypt the string in the first place. Okay, but why do it? Well, you have three good reasons to “hide” the implementation of an algorithm from its user
• Hiding the implementation stops people from fiddling with the input data to make the algorithm work differently. Such changes may be meant to make the algorithm work correctly, but can easily mess it up; either way, the meddling masks possible bugs from the developers

#include <stdio.h>

#include <string>
class StringCoding

{

private:

// The key to use in encrypting the string

std::string sKey;

public:

// The constructor, uses a preset key

StringCoding( void ) { sKey = “ATest”; }

// Main constructor, allows the user to specify a key

StringCoding( const char *strKey )

{

if ( strKey ) sKey = strKey;

else sKey = “ATest”; }

// Copy constructor StringCoding

( const StringCoding& aCopy ) { sKey = aCopy.sKey; }

public:

// Methods std::string Encode( const char *strIn );

std::string Decode( const char *strIn );

private:

std::string Xor( const char *strIn );

};

std::string StringCoding::Xor( const char *strIn )

{

std::string sOut = “”;
int nIndex = 0;

for ( int i=0; i<(int)strlen(strIn); ++i )

{ char c = (strIn[i] ^ sKey[nIndex]);

sOut += c; nIndex ++;

if ( nIndex == sKey.length() ) nIndex = 0; }
return sOut;
}
// For XOR encoding, the encode and decode methods are the same.

std::string StringCoding::Encode( const char *strIn )

{ return Xor( strIn ); }
std::string StringCoding::Decode( const char *strIn )

{ return Xor( strIn ); }
int main(int argc, char **argv)

{ if ( argc < 2 )

{ printf(“Usage: ch1_1 inputstring1 [inputstring2...]\n”); exit(1); }
StringCoding key(“XXX”);
for ( int i=1; i<argc; ++i )

{ std::string sEncode = key.Encode( argv[i] ); printf(“Input String : [%s]\n”, argv[i] ); printf(“Encoded String: [%s]\n”, sEncode.c_str() ); std::string sDecode = key.Decode( sEncode.c_str() ); printf(“Decoded String: [%s]\n”, sDecode.c_str() ); }
printf(“%d strings encoded\n”, argc-1); return 0;
}

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Posted from my blog with SteemPress : http://thesight.co.za/2018/02/21/creating-implementing-encapsulated-class/

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