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,
  14               const struct printf_info *info,
  15               va_list *app)
  16 {
  17   Widget *w;
  18   char *buffer;
  19   int len;
  20
  21   /* Format the output into a string. */
  22   w = va_arg (*app, Widget *);
  23   len = asprintf (&buffer, "<Widget %p: %s>", w, w->name);
  24   if (len == -1)
  25     return -1;
  26
  27   /* Pad to the minimum field width and print to the stream. */
  28   len = fprintf (stream, "%*s",
  29                  (info->left ? - info->width : info->width),
  30                  buffer);
  31
  32   /* Clean up and return. */
  33   free (buffer);
  34   return len;
  35 }
  36
  37
  38 int
  39 print_widget_arginfo (const struct printf_info *info, size_t n,
  40                       int *argtypes)
  41 {
  42   /* We always take exactly one argument and this is a pointer to the
  43      structure..  */
  44   if (n > 0)
  45     argtypes[0] = PA_POINTER;
  46   return 1;
  47 }
  48
  49
  50 int
  51 main (void)
  52 {
  53   /* Make a widget to print. */
  54   Widget mywidget;
  55   mywidget.name = "mywidget";
  56
  57   /* Register the print function for widgets. */
  58   register_printf_function ('W', print_widget, print_widget_arginfo);
  59
  60   /* Now print the widget. */
  61   printf ("|%W|\n", &mywidget);
  62   printf ("|%35W|\n", &mywidget);
  63   printf ("|%-35W|\n", &mywidget);
  64
  65   return 0;
  66 }