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/*
* BSD Zero Clause License
*
* Copyright (c) 2022 Thomas Voss
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
* OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
* PERFORMANCE OF THIS SOFTWARE.
*/
#define POSIXLY_CORRECT
#define _POSIX_C_SOURCE 200809L
#include <sys/ioctl.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define ESC 033
static void center(FILE *);
static int cols(void);
static int utf8len(const char *);
static int noesclen(const char *);
static int matchesc(const char *);
extern int optind;
extern char *optarg;
int rval;
long width;
int (*lenfunc)(const char *) = noesclen;
int
main(int argc, char **argv)
{
int opt;
char *endptr;
while ((opt = getopt(argc, argv, ":ew:")) != -1) {
switch (opt) {
case 'e':
lenfunc = utf8len;
break;
case 'w':
width = strtol(optarg, &endptr, 0);
if (*optarg == '\0' || *endptr != '\0')
errx(EXIT_FAILURE, "Invalid integer '%s'", optarg);
if (width <= 0)
errx(EXIT_FAILURE, "Width must be >0");
if (errno == ERANGE || width > INT_MAX)
warnx("Potential overflow of given width");
break;
default:
fprintf(stderr, "Usage: %s [-e] [-w width] [file ...]\n", argv[0]);
exit(EXIT_FAILURE);
}
}
if (!width && (width = cols()) == -1)
errx(EXIT_FAILURE, "Unable to determine output width");
argc -= optind;
argv += optind;
if (argc == 0)
center(stdin);
else do {
if (strcmp(*argv, "-") == 0)
center(stdin);
else {
FILE *fp;
if ((fp = fopen(*argv, "r")) == NULL) {
warn("fopen");
rval = EXIT_FAILURE;
} else {
center(fp);
fclose(fp);
}
}
} while (*++argv);
return rval;
}
/* Write the contents of the file pointed to by `fp' center aligned to the standard output */
void
center(FILE *fp)
{
static char *line = NULL;
static size_t bs = 0;
while (getline(&line, &bs, fp) != -1) {
int len, tabs = 0;
char *match = line;
while (strchr(match, '\t')) {
match++;
tabs++;
}
len = lenfunc(line) + tabs * 8 - tabs;
for (int i = (width - len) / 2; i; i--)
putchar(' ');
fputs(line, stdout);
}
if (ferror(fp)) {
warn("getline");
rval = EXIT_FAILURE;
}
}
/* Return the column width of the output device if it is a TTY. If it is not a TTY then return -1 */
int
cols(void)
{
struct winsize w;
if (!isatty(STDOUT_FILENO))
return -1;
if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &w) == -1)
err(EXIT_FAILURE, "ioctl");
return w.ws_col;
}
/* Return the length of the UTF-8 encoded string `s' in characters, not bytes */
int
utf8len(const char *s)
{
int l = 0;
while (*s)
l += (*s++ & 0xC0) != 0x80;
if (l > 0 && s[-1] == '\n')
l--;
return l;
}
/* Return the length of the UTF-8 encoded string `s' in characters, not bytes. Additionally this
* function ignores ANSI color escape sequences when computing the length.
*/
int
noesclen(const char *s)
{
int off = 0;
const char *d = s;
while ((d = strchr(d, ESC)) != NULL)
off += matchesc(++d);
return utf8len(s) - off;
}
/* Return the length of the ANSI color escape sequence at the beginning of the string `s'. If no
* escape sequence is matched then 0 is returned. The local variable `c' is initialized to 3 in order
* to account for the leading ESC, the following `[', and the trailing `m'.
*/
int
matchesc(const char *s)
{
int c = 3;
if (*s++ != '[')
return 0;
while (isdigit(*s) || *s == ';') {
c++;
s++;
}
return *s == 'm' ? c : 0;
}
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