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/*
* A Four Square cipher decoder. (Don't look directly at the mess)
*
* Copyright (C) 2014 Tomasz Kramkowski <tk@the-tk.com>
*
* This program is free software. It is licensed under version 3 of the
* GNU General Public License.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see [http://www.gnu.org/licenses/].
*/
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#define Q ('Q'-'A')
typedef struct vec2 {
int x;
int y;
} Vec2;
int increinc(int *);
void allupper(char *);
void genkey(char *, char *);
Vec2 *newVec2(const int, const int);
int main(int argc, char **argv)
{
int x, y, c=0;
if(argc!=4){
printf("Usage: %s <key1> <key2> <cipher>", *argv);
exit(1);
}
printf("%s, %s ", *(argv+1), *(argv+2));
char *trkey = *(argv+1);
allupper(trkey);
char *trfullkey = malloc(26);
genkey(trkey, trfullkey);
char *blkey = *(argv+2);
allupper(blkey);
char *blfullkey = malloc(26);
genkey(blkey, blfullkey);
char *cipher = *(argv+3);
allupper(cipher);
int i=0;
Vec2 *trtable[25];
for(x=0; x<5; x++)
for(y=0; y<5; y++)
trtable[trfullkey[i++]-'A'] = newVec2(x, y);
free(trfullkey);
i = 0;
Vec2 *bltable[25];
for(x=0; x<5; x++)
for(y=0; y<5; y++)
bltable[blfullkey[i++]-'A'] = newVec2(x, y);
free(blfullkey);
char basetable[5][5];
for(x=0; x<5; x++)
for(y=0; y<5; y++){
if(c==Q)
c++;
basetable[x][y] = 'A' + c++;
}
for(i=0; i<strlen(cipher)/2; i++){
char c1 = cipher[2*i];
char c2 = cipher[2*i+1];
putchar(basetable[trtable[c1-'A']->x][bltable[c2-'A']->y]);
putchar(basetable[bltable[c2-'A']->x][trtable[c1-'A']->y]);
}
putchar('\n');
for(i=0; i++; i<25){
free(trtable[i]);
free(bltable[i]);
}
return 0;
}
int increinc(int *num)
{
(*num)++;
return (*num)++;
}
void allupper(char *input)
{
int i;
for(i=0; i<strlen(input); i++)
if(isalpha(input[i]))
input[i]=toupper(input[i]);
}
void genkey(char *input, char *output)
{
int dict[26];
memset(dict, 0, 26*sizeof(int));
int i, outpt = 0;
for(i=0; i<strlen(input); i++){
if(!dict[input[i]-'A']){
output[outpt++]=input[i];
}
dict[input[i]-'A'] += 1;
}
for(i=0; i<26; i++)
if(!dict[i] && i!=Q)
output[outpt++]=i+'A';
output[outpt]='\0';
}
Vec2 *newVec2(const int x, const int y)
{
Vec2 *v = malloc(sizeof(Vec2));
v->x = x;
v->y = y;
return v;
}
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