1 #define PERL_NO_GET_CONTEXT
2 
3 #include "EXTERN.h"
4 #include "perl.h"
5 #include "XSUB.h"
6 
7 /* support for Hash::Util::FieldHash, prefix HUF_ */
8 
9 /* A Perl sub that returns a hashref to the object registry */
10 #define HUF_OB_REG "Hash::Util::FieldHash::_ob_reg"
11 /* Identifier for PERL_MAGIC_ext magic */
12 #define HUF_IDCACHE 0x4944
13 
14 /* For global cache of object registry */
15 #define MY_CXT_KEY "Hash::Util::FieldHash::_guts" XS_VERSION
16 typedef struct {
17     HV* ob_reg; /* Cache object registry */
18 } my_cxt_t;
19 START_MY_CXT
20 
21 /* Inquire the object registry (a lexical hash) from perl */
22 static HV *
23 HUF_get_ob_reg(pTHX) {
24     dSP;
25     HV* ob_reg = NULL;
26     I32 items;
27     ENTER;
28     SAVETMPS;
29 
30     PUSHMARK(SP);
31     items = call_pv(HUF_OB_REG, G_SCALAR|G_NOARGS);
32     SPAGAIN;
33 
34     if (items == 1 && TOPs && SvROK(TOPs) && SvTYPE(SvRV(TOPs)) == SVt_PVHV)
35         ob_reg = (HV*)SvRV(POPs);
36     PUTBACK;
37     FREETMPS;
38     LEAVE;
39 
40     if (!ob_reg)
41         Perl_die(aTHX_ "Can't get object registry hash");
42     return ob_reg;
43 }
44 
45 /* Deal with global context */
46 #define HUF_INIT 1
47 #define HUF_CLONE 0
48 #define HUF_RESET -1
49 
50 static void
51 HUF_global(pTHX_ I32 how) {
52     if (how == HUF_INIT) {
53         MY_CXT_INIT;
54         MY_CXT.ob_reg = HUF_get_ob_reg(aTHX);
55     } else if (how == HUF_CLONE) {
56         MY_CXT_CLONE;
57         MY_CXT.ob_reg = HUF_get_ob_reg(aTHX);
58     } else if (how == HUF_RESET) {
59         dMY_CXT;
60         MY_CXT.ob_reg = HUF_get_ob_reg(aTHX);
61     }
62 }
63 
64 /* Object id */
65 
66 /* definition of id transformation */
67 #define HUF_OBJ_ID(x) newSVuv(PTR2UV(x))
68 
69 static SV *
70 HUF_obj_id(pTHX_ SV *obj) {
71     SV *item = SvRV(obj);
72     MAGIC *mg;
73     SV *id;
74 
75     /* Get cached object ID, if it exists */
76     if (SvTYPE(item) >= SVt_PVMG) {
77         for ( mg = SvMAGIC(item); mg; mg = mg->mg_moremagic ) {
78             if ((mg->mg_type == PERL_MAGIC_ext) &&
79                 (mg->mg_private == HUF_IDCACHE)
80             ) {
81                 return mg->mg_obj;
82             }
83         }
84     }
85 
86     /* Create an object ID, cache it */
87     id = HUF_OBJ_ID(item);
88     mg = sv_magicext(item, id, PERL_MAGIC_ext, NULL, NULL, 0);
89     mg->mg_private = HUF_IDCACHE;
90     SvREFCNT_dec(id); /* refcnt++ in sv_magicext() */
91 
92     /* Return the object ID */
93     return id;
94 }
95 
96 /* set up uvar magic for any sv */
97 static void
98 HUF_add_uvar_magic(
99     pTHX_
100     SV* sv,                    /* the sv to enchant, visible to get/set */
101     I32(* val)(pTHX_ IV, SV*), /* "get" function */
102     I32(* set)(pTHX_ IV, SV*), /* "set" function */
103     I32 index,                 /* get/set will see this */
104     SV* thing                  /* any associated info */
105 ) {
106     struct ufuncs uf;
107         uf.uf_val = val;
108         uf.uf_set = set;
109         uf.uf_index = index;
110     sv_magic(sv, thing, PERL_MAGIC_uvar, (char*)&uf, sizeof(uf));
111 }
112 
113 /* Fetch the data container of a trigger */
114 static AV *
115 HUF_get_trigger_content(pTHX_ SV *trigger) {
116     MAGIC* mg;
117     if (trigger && (mg = mg_find(trigger, PERL_MAGIC_uvar)))
118         return (AV*)mg->mg_obj;
119     return NULL;
120 }
121 
122 /* Delete an object from all field hashes it may occur in.  Also delete
123  * the object's entry from the object registry.  This function goes in
124  * the uf_set field of the uvar magic of a trigger.
125  */
126 static I32 HUF_destroy_obj(pTHX_ IV index, SV *trigger) {
127     PERL_UNUSED_ARG(index);
128     /* Do nothing if the weakref wasn't undef'd.  Also don't bother
129      * during global destruction.  (MY_CXT.ob_reg is sometimes funny there) */
130     if (!SvROK(trigger) && (!PL_in_clean_all)) {
131         dMY_CXT;
132         AV* cont = HUF_get_trigger_content(aTHX_ trigger);
133         SV* ob_id = *av_fetch(cont, 0, 0);
134         HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
135         HE* ent;
136         hv_iterinit(field_tab);
137         while ((ent = hv_iternext(field_tab))) {
138             SV* field_ref = HeVAL(ent);
139             SV* field = SvRV(field_ref);
140             (void) hv_delete_ent((HV*)field, ob_id, 0, 0);
141         }
142         /* make it safe in case we must run in global clenaup, after all */
143         if (PL_in_clean_all)
144             HUF_global(aTHX_ HUF_RESET); /* shoudn't be needed */
145         (void) hv_delete_ent(MY_CXT.ob_reg, ob_id, 0, 0);
146     }
147     return 0;
148 }
149 
150 /* Create a trigger for an object.  The trigger is a magical SV
151  * that holds a weak ref to the object.  The magic fires when the object
152  * expires and takes care of garbage collection in registred hashes.
153  * For that purpose, the magic structure holds the original id of
154  * the object, and a list (a hash, really) of hashes from which the
155  * object may * have to be deleted.  The trigger is stored in the
156  * object registry and is also deleted when the object expires.
157  */
158 static SV *
159 HUF_new_trigger(pTHX_ SV *obj, SV *ob_id) {
160     dMY_CXT;
161     SV* trigger = sv_rvweaken(newRV_inc(SvRV(obj)));
162     AV* cont = newAV();
163     sv_2mortal((SV*)cont);
164     av_store(cont, 0, SvREFCNT_inc(ob_id));
165     av_store(cont, 1, (SV*)newHV());
166     HUF_add_uvar_magic(aTHX_ trigger, NULL, &HUF_destroy_obj, 0, (SV*)cont);
167     (void) hv_store_ent(MY_CXT.ob_reg, ob_id, trigger, 0);
168     return trigger;
169 }
170 
171 /* retrieve a trigger for obj if one exists, return NULL otherwise */
172 static SV *
173 HUF_ask_trigger(pTHX_ SV *ob_id) {
174     dMY_CXT;
175     HE* ent;
176     if ((ent = hv_fetch_ent(MY_CXT.ob_reg, ob_id, 0, 0)))
177         return HeVAL(ent);
178     return NULL;
179 }
180 
181 static SV *
182 HUF_get_trigger(pTHX_ SV *obj, SV *ob_id) {
183     SV* trigger = HUF_ask_trigger(aTHX_ ob_id);
184     if (!trigger)
185         trigger = HUF_new_trigger(aTHX_ obj, ob_id);
186     return( trigger);
187 }
188 
189 /* mark an object (trigger) as having been used with a field
190    (a clenup-liability)
191 */
192 static void
193 HUF_mark_field(pTHX_ SV *trigger, SV *field) {
194     AV* cont = HUF_get_trigger_content(aTHX_ trigger);
195     HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
196     SV* field_ref = newRV_inc(field);
197     UV field_addr = PTR2UV(field);
198     (void) hv_store(field_tab, (char *)&field_addr, sizeof(field_addr), field_ref, 0);
199 }
200 
201 /* Determine, from the value of action, whether this call may create a new
202  * hash key */
203 #define HUF_WOULD_CREATE_KEY(x) ((x) != HV_DELETE && ((x) & (HV_FETCH_ISSTORE | HV_FETCH_LVALUE)))
204 
205 /* The key exchange functions.  They communicate with S_hv_magic_uvar_xkey
206  * in hv.c */
207 static I32 HUF_watch_key_safe(pTHX_ IV action, SV* field) {
208     MAGIC* mg = mg_find(field, PERL_MAGIC_uvar);
209     SV* keysv;
210     if (mg && (keysv = mg->mg_obj)) {
211         if (SvROK(keysv)) { /* ref key */
212             SV* ob_id = HUF_obj_id(aTHX_ keysv);
213             mg->mg_obj = ob_id; /* key replacement */
214             if (HUF_WOULD_CREATE_KEY(action)) {
215                 SV* trigger = HUF_get_trigger(aTHX_ keysv, ob_id);
216                 HUF_mark_field(aTHX_ trigger, field);
217             }
218         } else if (HUF_WOULD_CREATE_KEY(action)) { /* string key */
219             /* registered as object id? */
220             SV* trigger;
221             if (( trigger = HUF_ask_trigger(aTHX_ keysv)))
222                 HUF_mark_field(aTHX_ trigger, field);
223         }
224     } else {
225         Perl_die(aTHX_ "Rogue call of 'HUF_watch_key_safe'");
226     }
227     return 0;
228 }
229 
230 static I32 HUF_watch_key_id(pTHX_ IV action, SV* field) {
231     MAGIC* mg = mg_find(field, PERL_MAGIC_uvar);
232     SV* keysv;
233     PERL_UNUSED_ARG(action);
234     if (mg && (keysv = mg->mg_obj)) {
235         if (SvROK(keysv)) /* ref key */
236             mg->mg_obj = HUF_obj_id(aTHX_ keysv); /* key replacement */
237     } else {
238         Perl_die(aTHX_ "Rogue call of 'HUF_watch_key_id'");
239     }
240     return 0;
241 }
242 
243 static int HUF_func_2mode( I32(* val)(pTHX_ IV, SV*)) {
244     int ans = 0;
245     if (val == &HUF_watch_key_id)
246         ans = 1;
247     if (val == &HUF_watch_key_safe)
248         ans = 2;
249     return(ans);
250 }
251 
252 static I32(* HUF_mode_2func( int mode))(pTHX_ IV, SV*) {
253     I32(* ans)(pTHX_ IV, SV*) = NULL;
254     switch (mode) {
255         case 1:
256             ans = &HUF_watch_key_id;
257             break;
258         case 2:
259             ans = &HUF_watch_key_safe;
260             break;
261     }
262     return(ans);
263 }
264 
265 /* see if something is a field hash */
266 static int
267 HUF_get_status(pTHX_ HV *hash) {
268     int ans = 0;
269     if (hash && (SvTYPE(hash) == SVt_PVHV)) {
270         MAGIC* mg;
271         struct ufuncs* uf;
272         if ((mg = mg_find((SV*)hash, PERL_MAGIC_uvar)) &&
273             (uf = (struct ufuncs *)mg->mg_ptr) &&
274             (uf->uf_set == NULL)
275         ) {
276             ans = HUF_func_2mode(uf->uf_val);
277         }
278     }
279     return ans;
280 }
281 
282 /* Thread support.  These routines are called by CLONE (and nothing else) */
283 
284 /* Fix entries for one object in all field hashes */
285 static void
286 HUF_fix_trigger(pTHX_ SV *trigger, SV *new_id) {
287     AV* cont = HUF_get_trigger_content(aTHX_ trigger);
288     HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
289     HV* new_tab = newHV();
290     HE* ent;
291     SV* old_id = *av_fetch(cont, 0, 0);
292     hv_iterinit(field_tab);
293     while ((ent = hv_iternext(field_tab))) {
294         SV* field_ref = HeVAL(ent);
295         HV* field = (HV*)SvRV(field_ref);
296         UV field_addr = PTR2UV(field);
297         SV* val;
298         /* recreate field tab entry */
299         (void) hv_store(new_tab, (char *)&field_addr, sizeof(field_addr), SvREFCNT_inc(field_ref), 0);
300         /* recreate field entry, if any */
301         if ((val = hv_delete_ent(field, old_id, 0, 0)))
302             (void) hv_store_ent(field, new_id, SvREFCNT_inc(val), 0);
303     }
304     /* update the trigger */
305     av_store(cont, 0, SvREFCNT_inc(new_id));
306     av_store(cont, 1, (SV*)new_tab);
307 }
308 
309 /* Go over object registry and fix all objects.  Also fix the object
310  * registry.
311  */
312 static void
313 HUF_fix_objects(pTHX) {
314     dMY_CXT;
315     I32 i, len;
316     HE* ent;
317     AV* oblist = (AV*)sv_2mortal((SV*)newAV());
318     hv_iterinit(MY_CXT.ob_reg);
319     while((ent = hv_iternext(MY_CXT.ob_reg)))
320         av_push(oblist, SvREFCNT_inc(hv_iterkeysv(ent)));
321     len = av_tindex(oblist);
322     for (i = 0; i <= len; ++i) {
323         SV* old_id = *av_fetch(oblist, i, 0);
324         SV* trigger = hv_delete_ent(MY_CXT.ob_reg, old_id, 0, 0);
325         SV* obj = SvRV(trigger);
326         MAGIC *mg;
327 
328         SV* new_id = HUF_OBJ_ID(obj);
329 
330         /* Replace cached object ID with this new one */
331         for (mg = SvMAGIC(obj); mg; mg = mg->mg_moremagic) {
332             if ((mg->mg_type == PERL_MAGIC_ext) &&
333                     (mg->mg_private == HUF_IDCACHE)
334                 ) {
335                 mg->mg_obj = new_id;
336             }
337         }
338 
339         HUF_fix_trigger(aTHX_ trigger, new_id);
340         (void) hv_store_ent(MY_CXT.ob_reg, new_id, SvREFCNT_inc(trigger), 0);
341     }
342 }
343 
344 /* test support (not needed for functionality) */
345 
346 static SV* counter;
347 I32 HUF_inc_var(pTHX_ IV index, SV* which) {
348     PERL_UNUSED_ARG(index);
349     PERL_UNUSED_ARG(which);
350     sv_setiv(counter, 1 + SvIV(counter));
351     return 0;
352 }
353 
354 MODULE = Hash::Util::FieldHash          PACKAGE = Hash::Util::FieldHash
355 
356 BOOT:
357 {
358     HUF_global(aTHX_ HUF_INIT); /* create variables */
359 }
360 
361 int
362 _fieldhash(SV* href, int mode)
363 PROTOTYPE: $$
364 CODE:
365     HV* field;
366     RETVAL = 0;
367     if (mode &&
368         href && SvROK(href) &&
369         (field = (HV*)SvRV(href)) &&
370         SvTYPE(field) == SVt_PVHV
371     ) {
372 
373         HUF_add_uvar_magic(
374             aTHX_
375             SvRV(href),
376             HUF_mode_2func(mode),
377             NULL,
378             0,
379             NULL
380         );
381         RETVAL = HUF_get_status(aTHX_ field);
382     }
383 OUTPUT:
384     RETVAL
385 
386 void
387 id(SV* ref)
388 PROTOTYPE: $
389 PPCODE:
390     if (SvROK(ref)) {
391         XPUSHs(HUF_obj_id(aTHX_ ref));
392     } else {
393         XPUSHs(ref);
394     }
395 
396 SV*
397 id_2obj(SV* id)
398 PROTOTYPE: $
399 CODE:
400     SV* obj = HUF_ask_trigger(aTHX_ id);
401     if (obj) {
402         RETVAL = newRV_inc(SvRV(obj));
403     } else {
404         RETVAL = &PL_sv_undef;
405     }
406 OUTPUT:
407     RETVAL
408 
409 SV*
410 register(SV* obj, ...)
411 PROTOTYPE: $@
412 CODE:
413     SV* trigger;
414     int i;
415     RETVAL = NULL;
416     if (!SvROK(obj)) {
417         Perl_die(aTHX_ "Attempt to register a non-ref");
418     } else {
419         RETVAL = newRV_inc(SvRV(obj));
420     }
421     trigger = HUF_get_trigger(aTHX_ obj, HUF_obj_id(aTHX_ obj));
422     for (i = 1; i < items; ++ i) {
423         SV* field_ref = POPs;
424         if (SvROK(field_ref) && (SvTYPE(SvRV(field_ref)) == SVt_PVHV)) {
425             HUF_mark_field(aTHX_ trigger, SvRV(field_ref));
426         }
427     }
428 OUTPUT:
429     RETVAL
430 
431 void
432 CLONE(char* classname)
433 CODE:
434     if (strEQ(classname, "Hash::Util::FieldHash")) {
435         HUF_global(aTHX_ HUF_CLONE);
436         HUF_fix_objects(aTHX);
437     }
438 
439 void
440 _active_fields(SV* obj)
441 PPCODE:
442     if (SvROK(obj)) {
443         SV* ob_id = HUF_obj_id(aTHX_ obj);
444         SV* trigger = HUF_ask_trigger(aTHX_ ob_id);
445         if (trigger) {
446             AV* cont = HUF_get_trigger_content(aTHX_ trigger);
447             HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
448             HE* ent;
449             hv_iterinit(field_tab);
450             while ((ent = hv_iternext(field_tab))) {
451                 HV* field = (HV*)SvRV(HeVAL(ent));
452                 if (hv_exists_ent(field, ob_id, 0))
453                     XPUSHs(sv_2mortal(newRV_inc((SV*)field)));
454             }
455         }
456     }
457 
458 void
459 _test_uvar_get(SV* svref, SV* countref)
460 ALIAS:
461 _test_uvar_get = 1
462 _test_uvar_set = 2
463 _test_uvar_same = 3
464 CODE:
465     if (SvROK(svref) && SvROK(countref)) {
466         counter = SvRV(countref);
467         sv_setiv(counter, 0);
468         HUF_add_uvar_magic(
469             aTHX_
470             SvRV(svref),
471             ix & 1 ? &HUF_inc_var : 0,
472             ix & 2 ? &HUF_inc_var : 0,
473 	    0,
474             SvRV(countref)
475         );
476     }
477