modules/example_module.c

   1 /* example_module.c -- example module for vlock,
   2  *                     the VT locking program for linux
   3  *
   4  * This program is copyright (C) 2007 Frank Benkstein, and is free
   5  * software.  It comes without any warranty, to the extent permitted by
   6  * applicable law.  You can redistribute it and/or modify it under the
   7  * terms of the Do What The Fuck You Want To Public License, Version 2,
   8  * as published by Sam Hocevar.  See http://sam.zoy.org/wtfpl/COPYING
   9  * for more details.
  10  */
  11
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #include <unistd.h>
  16 #include <errno.h>
  17
  18 /* Do not use any vlock specific headers here unless you intend to
  19  * submit your module for inclusion. */
  20
  21 /* Include this header file to make sure the types of the dependencies
  22  * and hooks are correct. */
  23 #include "vlock_plugin.h"
  24
  25 /* Declare dependencies.  Please see PLUGINS for their meaning.  Empty
  26  * dependencies can be left out. */
  27 const char *preceeds[] = { "new", "all", NULL };
  28 /* const char *succeeds[]; */
  29 /* const char *requires[]; */
  30 /* const char *needs[]; */
  31 const char *depends[] = { "all", NULL };
  32 /* const char *conflicts[]; */
  33
  34 /* Every hook has a void** argument ctx_ptr.  When they are called
  35  * ctx_ptr points to the same location and *ctx_ptr is initially set to
  36  * NULL.  Hook functions should pass state by defining a context struct
  37  * and saving the pointer to it in *ctx_ptr instead of using global
  38  * variables.
  39  */
  40
  41 struct example_context {
  42   int a;
  43   int b;
  44 };
  45
  46 /* Do something that should happen at vlock's start here.  An error in
  47  * this hook aborts vlock. */
  48 bool vlock_start(void **ctx_ptr)
  49 {
  50   struct example_context *ctx = malloc(sizeof *ctx);
  51
  52   if (ctx == NULL)
  53     return false;
  54
  55   ctx->a = 23;
  56   ctx->b = 42;
  57
  58   /* Save the context for use by the other hooks. */
  59   *ctx_ptr = ctx;
  60
  61   return true;
  62 }
  63
  64 /* Hooks that are not implemented should not be defined. */
  65
  66 /* Start a screensaver type action before the password prompt after a
  67  * timeout.  This hook must not block! */
  68 /* bool vlock_save(void **); */
  69
  70 /* Abort a screensaver type action before the password prompt after a
  71  * timeout.  This hook must not block! */
  72 /* bool vlock_save_abort(void **); */
  73
  74 /* Do something at the end of vlock.  Error returns are ignored here. */
  75 bool vlock_end(void **ctx_ptr)
  76 {
  77   struct example_context *ctx = *ctx_ptr;
  78   bool result = true;
  79
  80   if (ctx != NULL) {
  81     result = (ctx->a == 23 && ctx->b == 42);
  82
  83     free(ctx);
  84
  85     if (!result)
  86       fprintf(stderr, "vlock-example_module: Whoops!\n");
  87   }
  88
  89   return result;
  90 }