#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/times.h>
#include "channel.h"

// the bigger this is, the better the algol
// yet the more memory is taken
#define KEYSIZE 24

// not to be called
char *repeat(char *key, int size)
{
   char *new = (char *)malloc(size);
   int i=0;
   while (strlen(key)<size) {
         strcpy(new+i,key);
	 i+=strlen(key);
	 size -=strlen(key);
   }
   strncpy(new+i,key,size);
   return new;
}

// to be called to generate a new set of private and 
// public key
void generate(KEY *private,KEY *public)
{
   int i;
   srand(times(NULL));
   *private = malloc(KEYSIZE);
   *public = malloc(KEYSIZE);
   for (i=0;i<(KEYSIZE-1);i++) {
	(*private)[i]=rand();
	(*public)[i]=256 - (*private)[i] ;
   }
   (*private)[i]='\0';
   (*public)[i]='\0';
}

// called with a key will encode or decode your buffer
void code(char *buf,int size,KEY key)
{
     int i;
     char *new = repeat(key,size);
     for (i=0;i<size;i++)
     {
	buf[i]=(char)((int)buf[i] + (int)new[i]) % 256;
     }
     free(new);
}