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85 lines
2.0 KiB
C
85 lines
2.0 KiB
C
/* Printf Extension Example
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Copyright (C) 1991-2020 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see <https://www.gnu.org/licenses/>.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <printf.h>
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/*@group*/
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typedef struct
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{
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char *name;
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}
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Widget;
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/*@end group*/
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int
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print_widget (FILE *stream,
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const struct printf_info *info,
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const void *const *args)
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{
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const Widget *w;
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char *buffer;
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int len;
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/* Format the output into a string. */
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w = *((const Widget **) (args[0]));
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len = asprintf (&buffer, "<Widget %p: %s>", w, w->name);
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if (len == -1)
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return -1;
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/* Pad to the minimum field width and print to the stream. */
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len = fprintf (stream, "%*s",
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(info->left ? -info->width : info->width),
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buffer);
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/* Clean up and return. */
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free (buffer);
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return len;
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}
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int
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print_widget_arginfo (const struct printf_info *info, size_t n,
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int *argtypes)
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{
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/* We always take exactly one argument and this is a pointer to the
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structure.. */
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if (n > 0)
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argtypes[0] = PA_POINTER;
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return 1;
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}
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int
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main (void)
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{
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/* Make a widget to print. */
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Widget mywidget;
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mywidget.name = "mywidget";
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/* Register the print function for widgets. */
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register_printf_function ('W', print_widget, print_widget_arginfo);
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/* Now print the widget. */
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printf ("|%W|\n", &mywidget);
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printf ("|%35W|\n", &mywidget);
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printf ("|%-35W|\n", &mywidget);
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return 0;
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}
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