libmainloop/defer.c

   1 /*
   2  * ion/libmainloop/defer.c
   3  *
   4  * Copyright (c) Tuomo Valkonen 1999-2009.
   5  *
   6  * See the included file LICENSE for details.
   7  */
   8
   9 /* This file contains routines for deferred execution of potentially
  10  * dangerous actions. They're called upon returning to the main
  11  * loop.
  12  */
  13
  14 #include <libtu/obj.h>
  15 #include <libtu/objp.h>
  16 #include <libtu/types.h>
  17 #include <libtu/misc.h>
  18 #include <libtu/dlist.h>
  19 #include <libtu/output.h>
  20 #include <libtu/locale.h>
  21 #include <libtu/debug.h>
  22 #include "defer.h"
  23
  24
  25 DECLSTRUCT(WDeferred){
  26     Watch watch;
  27     WDeferredAction *action;
  28     ExtlFn fn;
  29     WDeferred *next, *prev;
  30     WDeferred **list;
  31 };
  32
  33
  34 static WDeferred *deferred=NULL;
  35
  36
  37 #define N_DBUF 16
  38
  39 /* To avoid allocating memory all the time, we use a small
  40  * buffer that should be able to contain the small expected
  41  * number of simultaneous deferred actions.
  42  */
  43 static WDeferred dbuf[N_DBUF];
  44 static int dbuf_used=0;
  45
  46
  47 static WDeferred *alloc_defer()
  48 {
  49     int i;
  50
  51     /* Keeping it simple -- this naive loop should do it
  52      * as N_DBUF is small.
  53      */
  54     for(i=0; i<N_DBUF; i++){
  55         if(!(dbuf_used&(1<<i))){
  56             dbuf_used|=(1<<i);
  57             return dbuf+i;
  58         }
  59     }
  60     return ALLOC(WDeferred);
  61 }
  62
  63
  64 static void free_defer(WDeferred *d)
  65 {
  66     if(d>=dbuf && d<dbuf+N_DBUF){
  67         dbuf_used&=~1<<((d-dbuf)/sizeof(WDeferred));
  68         return;
  69     }
  70     FREE(d);
  71 }
  72
  73
  74 static void defer_watch_handler(Watch *w, Obj *UNUSED(obj))
  75 {
  76     WDeferred *d=(WDeferred*)w;
  77
  78     UNLINK_ITEM(*(WDeferred**)(d->list), d, next, prev);
  79
  80     free_defer(d);
  81
  82     D(warn(TR("Object destroyed while deferred actions are still pending.")));
  83 }
  84
  85
  86 static bool already_deferred(Obj *obj, WDeferredAction *action,
  87                              WDeferred *list)
  88 {
  89     WDeferred *d;
  90
  91     for(d=list; d!=NULL; d=d->next){
  92         if(d->action==action && d->watch.obj==obj)
  93             return TRUE;
  94     }
  95
  96     return FALSE;
  97 }
  98
  99
 100 bool mainloop_defer_action_on_list(Obj *obj, WDeferredAction *action,
 101                                    WDeferred **list)
 102 {
 103     WDeferred *d;
 104
 105     if(already_deferred(obj, action, *list))
 106         return TRUE;
 107
 108     d=alloc_defer();
 109
 110     if(d==NULL){
 111         warn_err();
 112         return FALSE;
 113     }
 114
 115     d->action=action;
 116     d->list=list;
 117     d->fn=extl_fn_none();
 118     watch_init(&(d->watch));
 119
 120     if(obj!=NULL)
 121         watch_setup(&(d->watch), obj, defer_watch_handler);
 122
 123     LINK_ITEM(*list, d, next, prev);
 124
 125     return TRUE;
 126 }
 127
 128
 129 bool mainloop_defer_action(Obj *obj, WDeferredAction *action)
 130 {
 131     return mainloop_defer_action_on_list(obj, action, &deferred);
 132 }
 133
 134
 135 bool mainloop_defer_destroy(Obj *obj)
 136 {
 137     if(OBJ_IS_BEING_DESTROYED(obj))
 138         return FALSE;
 139
 140     return mainloop_defer_action(obj, destroy_obj);
 141 }
 142
 143
 144 bool mainloop_defer_extl_on_list(ExtlFn fn, WDeferred **list)
 145 {
 146     WDeferred *d;
 147
 148     d=alloc_defer();
 149
 150     if(d==NULL){
 151         warn_err();
 152         return FALSE;
 153     }
 154
 155     d->action=NULL;
 156     d->list=list;
 157     d->fn=extl_ref_fn(fn);
 158     watch_init(&(d->watch));
 159
 160     LINK_ITEM(*list, d, next, prev);
 161
 162     return TRUE;
 163 }
 164
 165
 166 /*EXTL_DOC
 167  * Defer execution of \var{fn} until the main loop.
 168  */
 169 EXTL_SAFE
 170 EXTL_EXPORT_AS(mainloop, defer)
 171 bool mainloop_defer_extl(ExtlFn fn)
 172 {
 173     return mainloop_defer_extl_on_list(fn, &deferred);
 174 }
 175
 176
 177 static void do_execute(WDeferred *d)
 178 {
 179     Obj *obj=d->watch.obj;
 180     WDeferredAction *a=d->action;
 181     ExtlFn fn=d->fn;
 182
 183     watch_reset(&(d->watch));
 184     free_defer(d);
 185
 186     if(a!=NULL){
 187         /* The deferral should not be on the list, if there
 188          * was an object, and it got destroyed.
 189          */
 190         /*if(obj!=NULL)*/
 191         a(obj);
 192     }else if(fn!=extl_fn_none()){
 193         extl_call(fn, NULL, NULL);
 194         extl_unref_fn(fn);
 195     }
 196 }
 197
 198
 199 void mainloop_execute_deferred_on_list(WDeferred **list)
 200 {
 201     while(*list!=NULL){
 202         WDeferred *d=*list;
 203         UNLINK_ITEM(*list, d, next, prev);
 204         do_execute(d);
 205     }
 206 }
 207
 208
 209 void mainloop_execute_deferred()
 210 {
 211     mainloop_execute_deferred_on_list(&deferred);
 212 }
 213