manual/examples/rprintf.c

   1 #include <stdio.h>
   2 #include <printf.h>
   3 #include <stdarg.h>
   4
   5 /*@group*/
   6 typedef struct
   7   {
   8     char *name;
   9   } Widget;
  10 /*@end group*/
  11
  12 int
  13 print_widget (FILE *stream, const struct printf_info *info, va_list *app)
  14 {
  15   Widget *w;
  16   char *buffer;
  17   int len;
  18
  19   /* Format the output into a string. */
  20   w = va_arg (*app, Widget *);
  21   len = asprintf (&buffer, "<Widget %p: %s>", w, w->name);
  22   if (len == -1)
  23     return -1;
  24
  25   /* Pad to the minimum field width and print to the stream. */
  26   len = fprintf (stream, "%*s",
  27                  (info->left ? - info->width : info->width),
  28                  buffer);
  29
  30   /* Clean up and return. */
  31   free (buffer);
  32   return len;
  33 }
  34
  35
  36 int
  37 main (void)
  38 {
  39   /* Make a widget to print. */
  40   Widget mywidget;
  41   mywidget.name = "mywidget";
  42
  43   /* Register the print function for widgets. */
  44   register_printf_function ('W', print_widget, NULL); /* No arginfo.  */
  45
  46   /* Now print the widget. */
  47   printf ("|%W|\n", &mywidget);
  48   printf ("|%35W|\n", &mywidget);
  49   printf ("|%-35W|\n", &mywidget);
  50
  51   return 0;
  52 }