libassa  3.5.1
SigHandlers.cpp
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1 // -*- c++ -*-
2 //------------------------------------------------------------------------------
3 // SigHandlers.cpp
4 //------------------------------------------------------------------------------
5 // Copyright (C) 1997-2002 Vladislav Grinchenko
6 //
7 // This library is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU Library General Public
9 // License as published by the Free Software Foundation; either
10 // version 2 of the License, or (at your option) any later version.
11 //------------------------------------------------------------------------------
12 #include "assa/SigHandlers.h"
13 
14 using namespace ASSA;
15 
16 #if !defined(WIN32)
17 
18 //---------------------------------------------------------------------------
19 // static declarations
20 //---------------------------------------------------------------------------
21 
23 
24 void
26 sighandlers_dispatcher (int signum_)
27 {
28  trace_with_mask("SigHandlers::sighandlers_dispatch", SIGHAND);
29 
30  DL((SIGHAND,"==> Received signal # %d\n", signum_));
31  dispatch (signum_);
32 }
33 
34 int
36 install (int signum_,
37  EventHandler* new_hand_,
38  SigAction* new_disp_,
39  EventHandler** old_hand_,
40  SigAction* old_disp_)
41 {
42  /*
43  Retrieve current signal disposition. If 3rd party handler has
44  already been istalled, make CFUNC_Handler out of it, and put it in
45  the list with id=0.
46 
47  Add new_hand_ to the list. Has global sighandlers_dispatcher not
48  been installed yet, install it too.
49  */
50 
51  trace_with_mask("SigHandlers::install()", SIGHAND);
52 
53  if (!in_range(signum_) == -1) {
54  EL((ASSAERR,"in_range (%s) failed\n",signum_));
55  return -1;
56  }
57 
58  CFUNC_Handler* cfhp = NULL;
59  SigHandlersList* handlist = NULL;
60 
61  handlist = SigHandlersList::instance(signum_);
62 
63  /*--- Retrieve current signal disposition ---*/
64 
65  SigAction cd;
66  cd.retrieve_action(signum_);
67 
68  /*
69  Check whether 3rd party software has already installed
70  signal handler.
71  */
73  cd.handler() != SIG_IGN &&
74  cd.handler() != SIG_DFL )
75  {
76  /*
77  Looks like some other code got ahead of me and installed C-function
78  signal handler. Make a note of it.
79 
80  Create EventHandler to hold 3rd party handler. This handler will be
81  deleted only by SigHandlers::remove (NULL), when application demanded
82  to remove all of the handlers.
83  */
84  DL((SIGHAND,"Detected 3rd party \"C\" handler!\n"));
85 
86  cfhp = new CFUNC_Handler (cd.handler ());
87  handlist->cfunc_handler (cfhp);
88 
89  /*
90  Insert 3rd party handler in list of handlers
91  for this signal.
92  */
93  DL((SIGHAND,"Adding 3rd party \"C\" handler\n"));
94 
95  if ( handlist->insert (cfhp) == false ) {
96  EL((ASSAERR, "Failed to insert "\
97  "c_func_handler for signum %d\n", signum_));
98  delete (cfhp);
99  handlist->cfunc_handler (0);
100  return -1;
101  }
102  DL((SIGHAND,"Set size: %d\n", handlist->size () ));
103  }
104  /*--- Add new_hand_ to the list of handlers for signum_. ---*/
105 
106  DL((SIGHAND,"Adding EventHandler to the list\n"));
107 
108  if (handlist->insert (new_hand_) == false) {
109  /*---
110  I failed to install new handler and might have already
111  added 3rd party CFUNC_Handler to the list without altering
112  disposition - if that's true, clean up the list.
113  ---*/
114  EL((ASSAERR,"failed to add new_hand_ to handlers list\n"));
115 
116  if (handlist->seen_cfunc_handler () &&
117  handlist->size() == 1)
118  {
119  handlist->erase ();
120  handlist->cfunc_handler (0);
121  }
122  return -1;
123  }
124  DL((SIGHAND,"Set size: %d\n", handlist->size () ));
125 
126  /*--- Has sighandlers_dispatcher been already installed? ---*/
127 
129  return 0;
130  }
131  DL((SIGHAND,"Installing 'sighandlers_dispatcher'\n"));
132 
133  /*
134  Installing new disposition; if user forgot to give me one
135  then default will be used.
136  */
137  SigAction sa ((C_SIG_HANDLER) SIG_DFL);
138 
139  if (new_disp_ == 0) {
140  new_disp_ = &sa;
141  }
142 
144 
145  if (new_disp_->register_action (signum_, old_disp_) == -1) {
146  /*---
147  I failed to install sighandlers_dispatcher. Up to this
148  point, if application had conventional C handler installed,
149  it still remains active. Handlers list built so far is
150  meaningless - get rid of it. ---*/
151 
152  EL((ASSAERR,"register_action() error\n"));
153 
154  if (handlist->seen_cfunc_handler ()) {
155  handlist->erase ();
156  handlist->cfunc_handler (0);
157  delete cfhp;
158  }
159  handlist->erase (new_hand_);
160  return -1;
161  }
162  return 0;
163 }
164 
165 int
167 remove (int signum_, EventHandler* eh_,
168  SigAction* new_disp_, SigAction* old_disp_)
169 
170 {
171  trace_with_mask("SigHandlers::remove()", SIGHAND);
172 
173  if (in_range (signum_)) {
174  EL((ASSAERR, "singum_ %d is out of range\n", signum_));
175  return -1;
176  }
177 
178  CFUNC_Handler* Cfhp = NULL; // pointer to C-function event handler
179  EventHandler* ehp = NULL; // pointer to current event handler
180 
181  SigHandlersList& handlist = *(SigHandlersList::instance(signum_));
182 
183  if (eh_ == NULL) {
184  DL((SIGHAND,"Erasing the entire set\n"));
185  /*--- Erase an entire list. ---*/
186  handlist.erase ();
187  DL((SIGHAND,"Set size: %d\n", handlist.size ()));
188  }
189  else {
190  /*
191  Note: I cannot do erasure in the same loop for following reason:
192 
193  According to Stroustrup (Section 17.4.1.7):
194  "After erase(), the iterator cannot be used again because
195  the element to which it pointed is no longer there."
196 
197  According to STL Tutorial and Ref. Guide:
198  "The erase function invalidates all iterators to all
199  positions past the point of erasure."
200 
201  That's why here we first take care of id recycling and heap memory
202  deallocation, and only then clean() the map all at once.
203  */
205 
206  if ((it = handlist.find (eh_)) != handlist.end ()) {
207  DL((SIGHAND,"Removing EventHandler\n"));
208  ehp = (*it);
209  handlist.erase (it);
210  }
211  DL((SIGHAND,"Set size: %d\n", handlist.size () ));
212  }
213  /*--- If set is not empty, we're done ---*/
214  if (handlist.size ()) return 0;
215 
216  /* If map was emptied out, install new disposition
217  with the 3rd party "C" function handler, if we had it.
218  */
219  SigAction null_sa;
220  if (new_disp_ == 0) new_disp_ = &null_sa;
221 
222  DL((SIGHAND,"Handlers List is empty\n"));
223 
224  if (handlist.seen_cfunc_handler ()) {
225  /*--- Put 3rd party handler into disposition ---*/
226  DL((SIGHAND,"Reinstalling \"C\" handler\n"));
227  Cfhp = handlist.cfunc_handler (0);
228  new_disp_->handler (Cfhp->handler ());
229  delete Cfhp;
230  }
231  /*--- Install new disposition ---*/
232  return new_disp_->register_action (signum_, old_disp_);
233 }
234 
235 void
237 dispatch (int signum_)
238 {
239  trace_with_mask("SigHandlers::dispatch", SIGHAND);
240 
241  /*---
242  For every element in the set that holds all EventHandlers for
243  given signum, call its respective handle_signal() member function.
244  ---*/
245 
246  /*--- save errno ---*/
247  int errno_saved = errno;
248 
249  SigHandlersList& handlist = *(SigHandlersList::instance(signum_));
251  EventHandler* ehp;
252 
253  for (it=handlist.begin(); it != handlist.end(); it++) {
254  ehp = *it;
255  if (ehp->handle_signal (signum_) == -1) {
256  /*---
257  this event handler reported error when handling
258  signum - remove it from the set
259  ---*/
260  handlist.erase (it);
261  }
262  }
263  /*--- restore errno ---*/
264  errno = errno_saved;
265 }
266 
267 #endif // !defined(WIN32)
268 
#define EL(X)
A macro for writing error message to the Logger.
Definition: Logger.h:285
#define DL(X)
A macro for writing debug message to the Logger.
Definition: Logger.h:273
#define trace_with_mask(s, m)
trace_with_mask() is used to trace function call chain in C++ program.
Definition: Logger.h:437
void(* C_SIG_HANDLER)(int)
Definition: SigAction.h:28
SigHandlers is a signal handlers manager.
CFUNC_Handler class.
C_SIG_HANDLER handler()
EventHandler class.
Definition: EventHandler.h:103
virtual int handle_signal(int signum_)
Signal handler callback.
Definition: EventHandler.h:204
void handler(C_SIG_HANDLER sha_)
Set new signal handler to function pointer sha_.
Definition: SigAction.h:334
int retrieve_action(int signum_)
Retrieve current disposition for the signal signum_ into this object.
Definition: SigAction.h:381
int register_action(int signum_, SigAction *oaction_=0)
Register this object as current disposition for signal signum_, and store old disposition in oaction_...
Definition: SigAction.h:360
int in_range(int signum_)
Check that signum_ is in valid range.
Definition: SigHandler.cpp:27
SigHandlersList class.
set< key_type, CompSHL >::iterator iterator
static SigHandlersList * m_instance[NSIG]
Static map of signal numbers to SigHandlerLists.
iterator find(const key_type key_)
Find event handler by its pointer key_.
iterator begin()
Return an iterator pointing to the beginning of the list.
bool insert(data_type data_)
Add an event handler data_ to the list.
void erase(const key_type key_)
Find and remove event handler key_ from the list.
iterator end()
Return an iterator pointing to the end of the list.
CFUNC_Handler * cfunc_handler(CFUNC_Handler *cfp_)
Save 3rd party C function handler to remember.
size_t size() const
Size of the list.
static SigHandlersList * instance(int signum_)
Retrieve a pointer to the list of event handlers listening to signum_ signal delivery.
void seen_cfunc_handler(bool ft_)
Indicate whether 3rd party C function handler was installed.
static void sighandlers_dispatcher(int signum_)
A wrapper around static SigHandlers::dispatch().
Definition: SigHandlers.cpp:26
virtual int remove(int signum_, EventHandler *eh_, SigAction *new_disp_=0, SigAction *old_disp_=0)
Remove EventHandler from the list of registered handler for signum_.
virtual int install(int signum_, EventHandler *new_hand_, SigAction *new_disp_=0, EventHandler **old_hand_=0, SigAction *old_disp_=0)
Register EventHandler with dispatching system.
Definition: SigHandlers.cpp:36
static void dispatch(int signum_)
The heart of SigHandlers class - this callback function is really registered with OS to catch all of ...
Definition: Acceptor.h:40
@ SIGHAND
Class SigHandler(s) messages
Definition: LogMask.h:38
@ ASSAERR
ASSA and system errors
Definition: LogMask.h:34