libio/misc/hook.c

/*
 *  ircd-hybrid: an advanced Internet Relay Chat Daemon(ircd).
 *  hook.c: Provides a generic event hooking interface.
 *
 *  Copyright (C) 2003 Piotr Nizynski, Advanced IRC Services Project Team
 *  Copyright (C) 2005 Hybrid Development Team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 *  USA
 *
 *  $Id: hook.c 33 2005-10-02 20:50:00Z knight $
 */

#include "stdinc.h"
#include "hook.h"
#include "list.h"
#include "memory.h"
#include "tools.h"
#include "irc_string.h"
#include "s_misc.h"

dlink_list callback_list = {NULL, NULL, 0};

/*
 * register_callback()
 *
 * Creates a new callback.
 *
 * inputs:
 *   name  -  name used to identify the callback
 *            (can be NULL for anonymous callbacks)
 *   func  -  initial function attached to the chain
 *            (can be NULL to create an empty chain)
 * output: pointer to Callback structure or NULL if already exists
 *
 * NOTE: Once registered, a callback should never be freed!
 * That's because there may be modules which depend on it
 * (even if no functions are attached). That's also why
 * we dynamically allocate the struct here -- we don't want
 * to allow anyone to place it in module data, which can be
 * unloaded at any time.
 */
struct Callback *
register_callback(const char *name, CBFUNC *func)
{
  struct Callback *cb;

  if (name != NULL)
    if ((cb = find_callback(name)) != NULL)
    {
      /* re-attaching an empty hook chain? */
      if (!is_callback_present(cb))
      {
        dlinkAdd(func, MyMalloc(sizeof(dlink_node)), &cb->chain);
        return (cb);
      }
      return (NULL);
    }

  cb = MyMalloc(sizeof(struct Callback));
  if (func != NULL)
    dlinkAdd(func, MyMalloc(sizeof(dlink_node)), &cb->chain);
  if (name != NULL)
  {
    DupString(cb->name, name);
    dlinkAdd(cb, &cb->node, &callback_list);
  }
  return (cb);
}

/*
 * execute_callback()
 *
 * Passes control down the callback hook chain.
 *
 * inputs:
 *   callback  -  pointer to Callback structure
 *   param     -  argument to pass
 * output: function return value
 */
void *
execute_callback(struct Callback *cb, ...)
{
  void *res;
  va_list args;

  cb->called++;
  cb->last = CurrentTime;

  if (!is_callback_present(cb))
    return (NULL);

  va_start(args, cb);
  res = ((CBFUNC *) cb->chain.head->data)(args);
  va_end(args);
  return (res);
}

/*
 * pass_callback()
 *
 * Called by a hook function to pass code flow further
 * in the hook chain.
 *
 * inputs:
 *   this_hook  -  pointer to dlink_node of the current hook function
 *   ...        -  (original or modified) arguments to be passed
 * output: callback return value
 */
void *
pass_callback(dlink_node *this_hook, ...)
{
  void *res;
  va_list args;

  if (this_hook->next == NULL)
    return (NULL);  /* reached the last one */

  va_start(args, this_hook);
  res = ((CBFUNC *) this_hook->next->data)(args);
  va_end(args);
  return (res);
}

/*
 * find_callback()
 *
 * Finds a named callback.
 *
 * inputs:
 *   name  -  name of the callback
 * output: pointer to Callback structure or NULL if not found
 */
struct Callback *
find_callback(const char *name)
{
  struct Callback *cb;
  dlink_node *ptr;

  DLINK_FOREACH(ptr, callback_list.head)
  {
    cb = ptr->data;
    if (!irccmp(cb->name, name))
      return (cb);
  }

  return (NULL);
}

/*
 * install_hook()
 *
 * Installs a hook for the given callback.
 *
 * inputs:
 *   cb      -  pointer to Callback structure
 *   hook    -  address of hook function
 * output: pointer to dlink_node of the hook (used when
 *         passing control to the next hook in the chain);
 *         valid till uninstall_hook() is called
 *
 * NOTE: The new hook is installed at the beginning of the chain,
 * so it has full control over functions installed earlier.
 */
dlink_node *
install_hook(struct Callback *cb, CBFUNC *hook)
{
  dlink_node *node = MyMalloc(sizeof(dlink_node));

  dlinkAdd(hook, node, &cb->chain);
  return (node);
}

/*
 * uninstall_hook()
 *
 * Removes a specific hook for the given callback.
 *
 * inputs:
 *   cb      -  pointer to Callback structure
 *   hook    -  address of hook function
 * output: none
 */
void
uninstall_hook(struct Callback *cb, CBFUNC *hook)
{
  /* let it core if not found */
  dlink_node *ptr = dlinkFind(&cb->chain, hook);

  dlinkDelete(ptr, &cb->chain);
  MyFree(ptr);
}
Revision:	65
Committed:	Mon Oct 3 23:33:16 2005 UTC (20 years, 10 months ago) by adx
Content type:	text/x-csrc
File size:	4986 byte(s)
Log Message:	- removed external references from libio/misc - imported s_misc.c to libio, moved CurrentTime there
#	User	Rev	Content
1	adx	61	/*
2			* ircd-hybrid: an advanced Internet Relay Chat Daemon(ircd).
3			* hook.c: Provides a generic event hooking interface.
4			*
5			* Copyright (C) 2003 Piotr Nizynski, Advanced IRC Services Project Team
6			* Copyright (C) 2005 Hybrid Development Team
7			*
8			* This program is free software; you can redistribute it and/or modify
9			* it under the terms of the GNU General Public License as published by
10			* the Free Software Foundation; either version 2 of the License, or
11			* (at your option) any later version.
12			*
13			* This program is distributed in the hope that it will be useful,
14			* but WITHOUT ANY WARRANTY; without even the implied warranty of
15			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16			* GNU General Public License for more details.
17			*
18			* You should have received a copy of the GNU General Public License
19			* along with this program; if not, write to the Free Software
20			* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
21			* USA
22			*
23			* $Id: hook.c 33 2005-10-02 20:50:00Z knight $
24			*/
25
26			#include "stdinc.h"
27			#include "hook.h"
28			#include "list.h"
29			#include "memory.h"
30			#include "tools.h"
31			#include "irc_string.h"
32	adx	65	#include "s_misc.h"
33	adx	61
34			dlink_list callback_list = {NULL, NULL, 0};
35
36			/*
37			* register_callback()
38			*
39			* Creates a new callback.
40			*
41			* inputs:
42			* name - name used to identify the callback
43			* (can be NULL for anonymous callbacks)
44			* func - initial function attached to the chain
45			* (can be NULL to create an empty chain)
46			* output: pointer to Callback structure or NULL if already exists
47			*
48			* NOTE: Once registered, a callback should never be freed!
49			* That's because there may be modules which depend on it
50			* (even if no functions are attached). That's also why
51			* we dynamically allocate the struct here -- we don't want
52			* to allow anyone to place it in module data, which can be
53			* unloaded at any time.
54			*/
55			struct Callback *
56			register_callback(const char name, CBFUNC func)
57			{
58			struct Callback *cb;
59
60			if (name != NULL)
61			if ((cb = find_callback(name)) != NULL)
62			{
63			/* re-attaching an empty hook chain? */
64			if (!is_callback_present(cb))
65			{
66			dlinkAdd(func, MyMalloc(sizeof(dlink_node)), &cb->chain);
67			return (cb);
68			}
69			return (NULL);
70			}
71
72			cb = MyMalloc(sizeof(struct Callback));
73			if (func != NULL)
74			dlinkAdd(func, MyMalloc(sizeof(dlink_node)), &cb->chain);
75			if (name != NULL)
76			{
77			DupString(cb->name, name);
78			dlinkAdd(cb, &cb->node, &callback_list);
79			}
80			return (cb);
81			}
82
83			/*
84			* execute_callback()
85			*
86			* Passes control down the callback hook chain.
87			*
88			* inputs:
89			* callback - pointer to Callback structure
90			* param - argument to pass
91			* output: function return value
92			*/
93			void *
94			execute_callback(struct Callback *cb, ...)
95			{
96			void *res;
97			va_list args;
98
99			cb->called++;
100			cb->last = CurrentTime;
101
102			if (!is_callback_present(cb))
103			return (NULL);
104
105			va_start(args, cb);
106			res = ((CBFUNC *) cb->chain.head->data)(args);
107			va_end(args);
108			return (res);
109			}
110
111			/*
112			* pass_callback()
113			*
114			* Called by a hook function to pass code flow further
115			* in the hook chain.
116			*
117			* inputs:
118			* this_hook - pointer to dlink_node of the current hook function
119			* ... - (original or modified) arguments to be passed
120			* output: callback return value
121			*/
122			void *
123			pass_callback(dlink_node *this_hook, ...)
124			{
125			void *res;
126			va_list args;
127
128			if (this_hook->next == NULL)
129			return (NULL); /* reached the last one */
130
131			va_start(args, this_hook);
132			res = ((CBFUNC *) this_hook->next->data)(args);
133			va_end(args);
134			return (res);
135			}
136
137			/*
138			* find_callback()
139			*
140			* Finds a named callback.
141			*
142			* inputs:
143			* name - name of the callback
144			* output: pointer to Callback structure or NULL if not found
145			*/
146			struct Callback *
147			find_callback(const char *name)
148			{
149			struct Callback *cb;
150			dlink_node *ptr;
151
152			DLINK_FOREACH(ptr, callback_list.head)
153			{
154			cb = ptr->data;
155			if (!irccmp(cb->name, name))
156			return (cb);
157			}
158
159			return (NULL);
160			}
161
162			/*
163			* install_hook()
164			*
165			* Installs a hook for the given callback.
166			*
167			* inputs:
168			* cb - pointer to Callback structure
169			* hook - address of hook function
170			* output: pointer to dlink_node of the hook (used when
171			* passing control to the next hook in the chain);
172			* valid till uninstall_hook() is called
173			*
174			* NOTE: The new hook is installed at the beginning of the chain,
175			* so it has full control over functions installed earlier.
176			*/
177			dlink_node *
178			install_hook(struct Callback cb, CBFUNC hook)
179			{
180			dlink_node *node = MyMalloc(sizeof(dlink_node));
181
182			dlinkAdd(hook, node, &cb->chain);
183			return (node);
184			}
185
186			/*
187			* uninstall_hook()
188			*
189			* Removes a specific hook for the given callback.
190			*
191			* inputs:
192			* cb - pointer to Callback structure
193			* hook - address of hook function
194			* output: none
195			*/
196			void
197			uninstall_hook(struct Callback cb, CBFUNC hook)
198			{
199			/* let it core if not found */
200			dlink_node *ptr = dlinkFind(&cb->chain, hook);
201
202			dlinkDelete(ptr, &cb->chain);
203			MyFree(ptr);
204			}