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
16typedef struct {
17    HV* ob_reg; /* Cache object registry */
18} my_cxt_t;
19START_MY_CXT
20
21/* Inquire the object registry (a lexical hash) from perl */
22static HV *
23HUF_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
50static void
51HUF_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
69static SV *
70HUF_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 */
97static void
98HUF_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 */
114static AV *
115HUF_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 */
126static 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 */
158static SV *
159HUF_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 */
172static SV *
173HUF_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
181static SV *
182HUF_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*/
192static void
193HUF_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 */
207static 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
230static 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
243static 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
252static 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 */
266static int
267HUF_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 */
285static void
286HUF_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    I32 entries = hv_iterinit(field_tab);
293    hv_ksplit(new_tab, entries);
294    while ((ent = hv_iternext(field_tab))) {
295        SV* field_ref = HeVAL(ent);
296        HV* field = (HV*)SvRV(field_ref);
297        UV field_addr = PTR2UV(field);
298        SV* val;
299        /* recreate field tab entry */
300        (void) hv_store(new_tab, (char *)&field_addr, sizeof(field_addr), SvREFCNT_inc(field_ref), 0);
301        /* recreate field entry, if any */
302        if ((val = hv_delete_ent(field, old_id, 0, 0)))
303            (void) hv_store_ent(field, new_id, SvREFCNT_inc(val), 0);
304    }
305    /* update the trigger */
306    av_store(cont, 0, SvREFCNT_inc(new_id));
307    av_store(cont, 1, (SV*)new_tab);
308}
309
310/* Go over object registry and fix all objects.  Also fix the object
311 * registry.
312 */
313static void
314HUF_fix_objects(pTHX) {
315    dMY_CXT;
316    I32 i, len;
317    HE* ent;
318    AV* oblist = (AV*)sv_2mortal((SV*)newAV());
319    hv_iterinit(MY_CXT.ob_reg);
320    while((ent = hv_iternext(MY_CXT.ob_reg)))
321        av_push(oblist, SvREFCNT_inc(hv_iterkeysv(ent)));
322    len = av_count(oblist);
323    for (i = 0; i < len; ++i) {
324        SV* old_id = *av_fetch(oblist, i, 0);
325        SV* trigger = hv_delete_ent(MY_CXT.ob_reg, old_id, 0, 0);
326        SV* obj = SvRV(trigger);
327        MAGIC *mg;
328
329        SV* new_id = HUF_OBJ_ID(obj);
330
331        /* Replace cached object ID with this new one */
332        for (mg = SvMAGIC(obj); mg; mg = mg->mg_moremagic) {
333            if ((mg->mg_type == PERL_MAGIC_ext) &&
334                    (mg->mg_private == HUF_IDCACHE)
335                ) {
336                mg->mg_obj = new_id;
337            }
338        }
339
340        HUF_fix_trigger(aTHX_ trigger, new_id);
341        (void) hv_store_ent(MY_CXT.ob_reg, new_id, SvREFCNT_inc(trigger), 0);
342    }
343}
344
345/* test support (not needed for functionality) */
346
347static SV* counter;
348I32 HUF_inc_var(pTHX_ IV index, SV* which) {
349    PERL_UNUSED_ARG(index);
350    PERL_UNUSED_ARG(which);
351    sv_setiv(counter, 1 + SvIV(counter));
352    return 0;
353}
354
355MODULE = Hash::Util::FieldHash          PACKAGE = Hash::Util::FieldHash
356
357BOOT:
358{
359    HUF_global(aTHX_ HUF_INIT); /* create variables */
360}
361
362int
363_fieldhash(SV* href, int mode)
364PROTOTYPE: $$
365CODE:
366    HV* field;
367    RETVAL = 0;
368    if (mode &&
369        href && SvROK(href) &&
370        (field = (HV*)SvRV(href)) &&
371        SvTYPE(field) == SVt_PVHV
372    ) {
373
374        HUF_add_uvar_magic(
375            aTHX_
376            SvRV(href),
377            HUF_mode_2func(mode),
378            NULL,
379            0,
380            NULL
381        );
382        RETVAL = HUF_get_status(aTHX_ field);
383    }
384OUTPUT:
385    RETVAL
386
387void
388id(SV* ref)
389PROTOTYPE: $
390PPCODE:
391    if (SvROK(ref)) {
392        XPUSHs(HUF_obj_id(aTHX_ ref));
393    } else {
394        XPUSHs(ref);
395    }
396
397SV*
398id_2obj(SV* id)
399PROTOTYPE: $
400CODE:
401    SV* obj = HUF_ask_trigger(aTHX_ id);
402    if (obj) {
403        RETVAL = newRV_inc(SvRV(obj));
404    } else {
405        RETVAL = &PL_sv_undef;
406    }
407OUTPUT:
408    RETVAL
409
410SV*
411register(SV* obj, ...)
412PROTOTYPE: $@
413CODE:
414    SV* trigger;
415    int i;
416    RETVAL = NULL;
417    if (!SvROK(obj)) {
418        Perl_die(aTHX_ "Attempt to register a non-ref");
419    } else {
420        RETVAL = newRV_inc(SvRV(obj));
421    }
422    trigger = HUF_get_trigger(aTHX_ obj, HUF_obj_id(aTHX_ obj));
423    for (i = 1; i < items; ++ i) {
424        SV* field_ref = POPs;
425        if (SvROK(field_ref) && (SvTYPE(SvRV(field_ref)) == SVt_PVHV)) {
426            HUF_mark_field(aTHX_ trigger, SvRV(field_ref));
427        }
428    }
429OUTPUT:
430    RETVAL
431
432void
433CLONE(char* classname)
434CODE:
435    if (strEQ(classname, "Hash::Util::FieldHash")) {
436        HUF_global(aTHX_ HUF_CLONE);
437        HUF_fix_objects(aTHX);
438    }
439
440void
441_active_fields(SV* obj)
442PPCODE:
443    if (SvROK(obj)) {
444        SV* ob_id = HUF_obj_id(aTHX_ obj);
445        SV* trigger = HUF_ask_trigger(aTHX_ ob_id);
446        if (trigger) {
447            AV* cont = HUF_get_trigger_content(aTHX_ trigger);
448            HV* field_tab = (HV*) *av_fetch(cont, 1, 0);
449            HE* ent;
450            hv_iterinit(field_tab);
451            while ((ent = hv_iternext(field_tab))) {
452                HV* field = (HV*)SvRV(HeVAL(ent));
453                if (hv_exists_ent(field, ob_id, 0))
454                    XPUSHs(sv_2mortal(newRV_inc((SV*)field)));
455            }
456        }
457    }
458
459void
460_test_uvar_get(SV* svref, SV* countref)
461ALIAS:
462_test_uvar_get = 1
463_test_uvar_set = 2
464_test_uvar_same = 3
465CODE:
466    if (SvROK(svref) && SvROK(countref)) {
467        counter = SvRV(countref);
468        sv_setiv(counter, 0);
469        HUF_add_uvar_magic(
470            aTHX_
471            SvRV(svref),
472            ix & 1 ? &HUF_inc_var : 0,
473            ix & 2 ? &HUF_inc_var : 0,
474	    0,
475            SvRV(countref)
476        );
477    }
478