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/*
* Copyright (C) 2014 - 2016 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 <ctype.h>
#include <errno.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>
#include <string.h>
#define ACHAR_CNT 26
static noreturn void die(char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
exit(EXIT_FAILURE);
}
static int aclamp(long val)
{
while (val < 0)
val += ACHAR_CNT;
return val % ACHAR_CNT;
}
static int getrot(const char *str)
{
long val;
char *endptr;
if (!*str)
die("Invalid argument '%s'\n", str);
errno = 0;
val = strtol(str, &endptr, 10);
if (errno)
die("Invalid argument '%s': %s\n", str, strerror(errno));
if (*endptr)
die("Invalid argument '%s'\n", str);
return aclamp(val);
}
static int chval(int c)
{
switch (tolower(c)) {
case 'a': return 0;
case 'b': return 1;
case 'c': return 2;
case 'd': return 3;
case 'e': return 4;
case 'f': return 5;
case 'g': return 6;
case 'h': return 7;
case 'i': return 8;
case 'j': return 9;
case 'k': return 10;
case 'l': return 11;
case 'm': return 12;
case 'n': return 13;
case 'o': return 14;
case 'p': return 15;
case 'q': return 16;
case 'r': return 17;
case 's': return 18;
case 't': return 19;
case 'u': return 20;
case 'v': return 21;
case 'w': return 22;
case 'x': return 23;
case 'y': return 24;
case 'z': return 25;
}
return -1;
}
static int valch(int c, bool upper)
{
static const char chars[] = "abcdefghijklmnopqrstuvwxyz";
int ret;
if (c < 0 || c > 25)
return 0;
ret = chars[aclamp(c)];
if (upper)
ret = toupper(ret);
return ret;
}
static int rot(int c, int r)
{
return valch(aclamp(chval(c) + r), isupper(c));
}
int main(int argc, char **argv)
{
int r, c;
if (argc != 2)
die("Usage: %s <rotation>\n", argv[0]);
r = getrot(argv[1]);
while (c = getchar(), c != EOF) {
if (isalpha(c))
putchar(rot(c, r));
else
putchar(c);
}
return 0;
}
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