center.c

   1 #define _POSIX_C_SOURCE 200809L
   2 #define _XOPEN_SOURCE
   3 #include <stdio.h>
   4 #include <wchar.h>
   5 #include <stdlib.h>
   6 #include <termios.h>
   7 #include <unistd.h>
   8 #include <sys/ioctl.h>
   9 #include <locale.h>
  10
  11 #define ERR(str) { perror(str); err = EXIT_FAILURE; goto end; }
  12
  13 int main()
  14 {
  15         if (setlocale(LC_ALL, "") == NULL) {
  16                 perror("setlocale");
  17                 exit(EXIT_FAILURE);
  18         }
  19
  20         char *buf = NULL;
  21         size_t siz = 0;
  22         ssize_t len;
  23         int err = EXIT_SUCCESS;
  24
  25         while ((len = getline(&buf, &siz, stdin)) > 0) {
  26                 struct winsize ws;
  27                 if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) < 0) ERR("ioctl")
  28
  29                 int term_width = ws.ws_col;
  30
  31                 char *ptr = buf;
  32                 char *last = ptr;
  33                 int str_width = 0;
  34                 mbstate_t mbs = {0};
  35
  36                 while (len > 0) {
  37                         wchar_t wc;
  38
  39                         size_t adv = mbrtowc(&wc, ptr, len, &mbs);
  40                         if (adv == (size_t) -1 || adv == (size_t) -2) ERR("mbrtowc")
  41
  42                         int width = wcwidth(wc);
  43                         if (width > 0)
  44                                 str_width += width;
  45
  46                         if (*ptr == '\n' || str_width >= term_width - 12) {
  47                                 for (int i = (term_width - str_width) / 2; i > 0; i--)
  48                                         putchar(' ');
  49                                 fwrite(last, 1, ptr - last + 1, stdout);
  50
  51                                 if (*ptr != '\n')
  52                                         putchar('\n');
  53
  54                                 last = ptr + adv;
  55                                 str_width = 0;
  56                         }
  57
  58                         ptr += adv;
  59                         len -= adv;
  60                 }
  61         }
  62
  63         end:
  64         if (buf)
  65                 free(buf);
  66
  67         return err;
  68 }