// block.cpp : Defines the entry point for the console application.
//

#include <stdio.h>

#pragma warning(disable:4996)

typedef unsigned __int8   BYT;
typedef unsigned __int16  SYL;
typedef unsigned __int32  WRD;
typedef unsigned __int64  BIG;

typedef union
{ WRD wrd;
  SYL syl[2];
  BYT byt[4];
  BYT mat[2][2];
} BLK;

WRD atow(char* str)
{ char chr;
  WRD w=0;
  while (chr=*str++)
  { if (chr<='0' && chr>='9') break;
    w=w*10+(chr-'0'); }
  return w; }

int getblk(FILE* ori,BLK& blk)
{ int chr;
  int k=0;
  blk.wrd=0;
  while (k<4)
  { chr=fgetc(ori);
    if (chr == EOF) break;
    blk.byt[k++]=chr; }
  return k; }

void encblk(BLK& blk,WRD key)
{ blk.wrd=blk.wrd^key; }

void putblk(FILE* trg,BLK& blk)
{ int k=0;
  while (k<4)
  { fputc(blk.byt[k++],trg); } }

void encrypt(FILE *ori,FILE *trg,WRD key)
{ BLK blk;
  while (getblk(ori,blk))
  { encblk(blk,key);
    putblk(trg,blk); } }

int main(int argc, char* argv[])
{ FILE *ori,*trg;
  WRD key;
  if (argc<4)
  { printf("block <ori file> <targ file> <key>\n");
    return 0; }
  ori = fopen(argv[1],"rb");
  if (!ori)
  { printf("Unable to open ori file %s\n",argv[1]);
    return 1; }
  trg = fopen(argv[2],"wb");
  if (!trg)
  { printf("Unable to open trg file %s\n",argv[2]);
    fclose(ori);
    return 2; }
  key=atow(argv[3]);
  printf("key: %d\n",key);
  encrypt(ori,trg,key);
  fclose(trg);
  fclose(ori);
  return 0; }