manual/examples/rprintf.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <printf.h>
   4
   5 /*@group*/
   6 typedef struct
   7 {
   8   char *name;
   9 }
  10 Widget;
  11 /*@end group*/
  12
  13 int
  14 print_widget (FILE *stream,
  15               const struct printf_info *info,
  16               const void *const *args)
  17 {
  18   const Widget *w;
  19   char *buffer;
  20   int len;
  21
  22   /* Format the output into a string. */
  23   w = *((const Widget **) (args[0]));
  24   len = asprintf (&buffer, "<Widget %p: %s>", w, w->name);
  25   if (len == -1)
  26     return -1;
  27
  28   /* Pad to the minimum field width and print to the stream. */
  29   len = fprintf (stream, "%*s",
  30                  (info->left ? -info->width : info->width),
  31                  buffer);
  32
  33   /* Clean up and return. */
  34   free (buffer);
  35   return len;
  36 }
  37
  38
  39 int
  40 print_widget_arginfo (const struct printf_info *info, size_t n,
  41                       int *argtypes)
  42 {
  43   /* We always take exactly one argument and this is a pointer to the
  44      structure..  */
  45   if (n > 0)
  46     argtypes[0] = PA_POINTER;
  47   return 1;
  48 }
  49
  50
  51 int
  52 main (void)
  53 {
  54   /* Make a widget to print. */
  55   Widget mywidget;
  56   mywidget.name = "mywidget";
  57
  58   /* Register the print function for widgets. */
  59   register_printf_function ('W', print_widget, print_widget_arginfo);
  60
  61   /* Now print the widget. */
  62   printf ("|%W|\n", &mywidget);
  63   printf ("|%35W|\n", &mywidget);
  64   printf ("|%-35W|\n", &mywidget);
  65
  66   return 0;
  67 }