//-------------------------------------------------------------------
//	encrypt.cpp
//
//	This program can act as a pipe to perform simple encryption.  
//
//		Usage example:  $ cat message.txt | encrypt 
//
//	programmer: ALLAN CRUSE
//	written on: 14 DEC 2004
//-------------------------------------------------------------------

#include <unistd.h>	// for read(), write() 


int main( int argc, char **argv )
{
	// initialize the cipher array (with ascii codes)
	char cipher[ 256 ];
	for (int i = 0; i < 256; i++) cipher[ i ] = i;

	// scramble the translations for uppercase letters
	for (int i = 0; i < 26; i++)
		cipher[ 'A' + i ] = 'A' + ( i + 17 )%26;

	// scramble the translations for lowercase letters
	for (int i = 0; i < 26; i++)
		cipher[ 'a' + i ] = 'a' + ( i + 23 )%26;
		
	// scramble the translations for decimal numerals
	for (int i = 0; i < 10; i++)
		cipher[ '0' + i ] = '0' + ( i + 4 )%10;

	// output the translation for each character read
	char	ch;
	while ( read( 0, &ch, 1 ) == 1 )
		write( 1, &cipher[ ch ], 1 );
}