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/cvs/Coro/Coro/State.xs
Revision: 1.13
Committed: Mon Jul 23 22:09:39 2001 UTC (22 years, 10 months ago) by root
Branch: MAIN
Changes since 1.12: +191 -78 lines
Log Message:
*** empty log message ***

File Contents

# Content
1 #include "EXTERN.h"
2 #include "perl.h"
3 #include "XSUB.h"
4
5 #include "libcoro/coro.c"
6
7 #ifdef HAVE_MMAP
8 # include <unistd.h>
9 # include <sys/mman.h>
10 #endif
11
12 #define MAY_FLUSH /* increases codesize */
13
14 #define SUB_INIT "Coro::State::initialize"
15
16 #define TRANSFER_SAVE_DEFAV 0x00000001
17 #define TRANSFER_SAVE_DEFSV 0x00000002
18 #define TRANSFER_SAVE_ERRSV 0x00000004
19 #define TRANSFER_SAVE_CCTXT 0x00000008
20
21 #define TRANSFER_SAVE_ALL -1
22
23 struct coro {
24 /* the optional C context */
25 coro_context cctx;
26 void *sptr;
27 long ssize;
28
29 /* optionally saved, might be zero */
30 AV *defav;
31 SV *defsv;
32 SV *errsv;
33
34 /* saved global state not related to stacks */
35 U8 dowarn;
36
37 /* the stacks and related info (callchain etc..) */
38 PERL_SI *curstackinfo;
39 AV *curstack;
40 AV *mainstack;
41 SV **stack_sp;
42 OP *op;
43 SV **curpad;
44 SV **stack_base;
45 SV **stack_max;
46 SV **tmps_stack;
47 I32 tmps_floor;
48 I32 tmps_ix;
49 I32 tmps_max;
50 I32 *markstack;
51 I32 *markstack_ptr;
52 I32 *markstack_max;
53 I32 *scopestack;
54 I32 scopestack_ix;
55 I32 scopestack_max;
56 ANY *savestack;
57 I32 savestack_ix;
58 I32 savestack_max;
59 OP **retstack;
60 I32 retstack_ix;
61 I32 retstack_max;
62 COP *curcop;
63 JMPENV start_env;
64 JMPENV *top_env;
65
66 /* data associated with this coroutine (initial args) */
67 AV *args;
68 };
69
70 typedef struct coro *Coro__State;
71 typedef struct coro *Coro__State_or_hashref;
72
73 static AV *main_mainstack; /* used to differentiate between $main and others */
74 static HV *coro_state_stash;
75 static HV *padlist_cache;
76
77 /* mostly copied from op.c:cv_clone2 */
78 STATIC AV *
79 clone_padlist (AV *protopadlist)
80 {
81 AV *av;
82 I32 ix;
83 AV *protopad_name = (AV *) * av_fetch (protopadlist, 0, FALSE);
84 AV *protopad = (AV *) * av_fetch (protopadlist, 1, FALSE);
85 SV **pname = AvARRAY (protopad_name);
86 SV **ppad = AvARRAY (protopad);
87 I32 fname = AvFILLp (protopad_name);
88 I32 fpad = AvFILLp (protopad);
89 AV *newpadlist, *newpad_name, *newpad;
90 SV **npad;
91
92 newpad_name = newAV ();
93 for (ix = fname; ix >= 0; ix--)
94 av_store (newpad_name, ix, SvREFCNT_inc (pname[ix]));
95
96 newpad = newAV ();
97 av_fill (newpad, AvFILLp (protopad));
98 npad = AvARRAY (newpad);
99
100 newpadlist = newAV ();
101 AvREAL_off (newpadlist);
102 av_store (newpadlist, 0, (SV *) newpad_name);
103 av_store (newpadlist, 1, (SV *) newpad);
104
105 av = newAV (); /* will be @_ */
106 av_extend (av, 0);
107 av_store (newpad, 0, (SV *) av);
108 AvFLAGS (av) = AVf_REIFY;
109
110 for (ix = fpad; ix > 0; ix--)
111 {
112 SV *namesv = (ix <= fname) ? pname[ix] : Nullsv;
113 if (namesv && namesv != &PL_sv_undef)
114 {
115 char *name = SvPVX (namesv); /* XXX */
116 if (SvFLAGS (namesv) & SVf_FAKE || *name == '&')
117 { /* lexical from outside? */
118 npad[ix] = SvREFCNT_inc (ppad[ix]);
119 }
120 else
121 { /* our own lexical */
122 SV *sv;
123 if (*name == '&')
124 sv = SvREFCNT_inc (ppad[ix]);
125 else if (*name == '@')
126 sv = (SV *) newAV ();
127 else if (*name == '%')
128 sv = (SV *) newHV ();
129 else
130 sv = NEWSV (0, 0);
131 if (!SvPADBUSY (sv))
132 SvPADMY_on (sv);
133 npad[ix] = sv;
134 }
135 }
136 else if (IS_PADGV (ppad[ix]) || IS_PADCONST (ppad[ix]))
137 {
138 npad[ix] = SvREFCNT_inc (ppad[ix]);
139 }
140 else
141 {
142 SV *sv = NEWSV (0, 0);
143 SvPADTMP_on (sv);
144 npad[ix] = sv;
145 }
146 }
147
148 #if 0 /* return -ENOTUNDERSTOOD */
149 /* Now that vars are all in place, clone nested closures. */
150
151 for (ix = fpad; ix > 0; ix--) {
152 SV* namesv = (ix <= fname) ? pname[ix] : Nullsv;
153 if (namesv
154 && namesv != &PL_sv_undef
155 && !(SvFLAGS(namesv) & SVf_FAKE)
156 && *SvPVX(namesv) == '&'
157 && CvCLONE(ppad[ix]))
158 {
159 CV *kid = cv_clone((CV*)ppad[ix]);
160 SvREFCNT_dec(ppad[ix]);
161 CvCLONE_on(kid);
162 SvPADMY_on(kid);
163 npad[ix] = (SV*)kid;
164 }
165 }
166 #endif
167
168 return newpadlist;
169 }
170
171 #ifdef MAY_FLUSH
172 STATIC AV *
173 free_padlist (AV *padlist)
174 {
175 /* may be during global destruction */
176 if (SvREFCNT(padlist))
177 {
178 I32 i = AvFILLp(padlist);
179 while (i >= 0)
180 {
181 SV **svp = av_fetch(padlist, i--, FALSE);
182 SV *sv = svp ? *svp : Nullsv;
183 if (sv)
184 SvREFCNT_dec(sv);
185 }
186
187 SvREFCNT_dec((SV*)padlist);
188 }
189 }
190 #endif
191
192 /* the next two functions merely cache the padlists */
193 STATIC void
194 get_padlist (CV *cv)
195 {
196 SV **he = hv_fetch (padlist_cache, (void *)&cv, sizeof (CV *), 0);
197
198 if (he && AvFILLp ((AV *)*he) >= 0)
199 CvPADLIST (cv) = (AV *)av_pop ((AV *)*he);
200 else
201 CvPADLIST (cv) = clone_padlist (CvPADLIST (cv));
202 }
203
204 STATIC void
205 put_padlist (CV *cv)
206 {
207 SV **he = hv_fetch (padlist_cache, (void *)&cv, sizeof (CV *), 1);
208
209 if (SvTYPE (*he) != SVt_PVAV)
210 {
211 SvREFCNT_dec (*he);
212 *he = (SV *)newAV ();
213 }
214
215 av_push ((AV *)*he, (SV *)CvPADLIST (cv));
216 }
217
218 #ifdef MAY_FLUSH
219 STATIC void
220 flush_padlist_cache ()
221 {
222 HV *hv = padlist_cache;
223 padlist_cache = newHV ();
224
225 if (hv_iterinit (hv))
226 {
227 HE *he;
228 AV *padlist;
229
230 while (!!(he = hv_iternext (hv)))
231 {
232 AV *av = (AV *)HeVAL(he);
233
234 /* casting is fun. */
235 while (&PL_sv_undef != (SV *)(padlist = (AV *)av_pop (av)))
236 free_padlist (padlist);
237 }
238 }
239
240 SvREFCNT_dec (hv);
241 }
242 #endif
243
244 #define SB do {
245 #define SE } while (0)
246
247 #define LOAD(state) SB load_state(aTHX_ (state)); SPAGAIN; SE
248 #define SAVE(state,flags) SB PUTBACK; save_state(aTHX_ (state),(flags)); SE
249
250 #define REPLACE_SV(sv,val) SB SvREFCNT_dec(sv); (sv) = (val); SE
251
252 static void
253 load_state(pTHX_ Coro__State c)
254 {
255 PL_dowarn = c->dowarn;
256
257 PL_curstackinfo = c->curstackinfo;
258 PL_curstack = c->curstack;
259 PL_mainstack = c->mainstack;
260 PL_stack_sp = c->stack_sp;
261 PL_op = c->op;
262 PL_curpad = c->curpad;
263 PL_stack_base = c->stack_base;
264 PL_stack_max = c->stack_max;
265 PL_tmps_stack = c->tmps_stack;
266 PL_tmps_floor = c->tmps_floor;
267 PL_tmps_ix = c->tmps_ix;
268 PL_tmps_max = c->tmps_max;
269 PL_markstack = c->markstack;
270 PL_markstack_ptr = c->markstack_ptr;
271 PL_markstack_max = c->markstack_max;
272 PL_scopestack = c->scopestack;
273 PL_scopestack_ix = c->scopestack_ix;
274 PL_scopestack_max = c->scopestack_max;
275 PL_savestack = c->savestack;
276 PL_savestack_ix = c->savestack_ix;
277 PL_savestack_max = c->savestack_max;
278 PL_retstack = c->retstack;
279 PL_retstack_ix = c->retstack_ix;
280 PL_retstack_max = c->retstack_max;
281 PL_curcop = c->curcop;
282 PL_start_env = c->start_env;
283 PL_top_env = c->top_env;
284
285 if (c->defav) REPLACE_SV (GvAV (PL_defgv), c->defav);
286 if (c->defsv) REPLACE_SV (DEFSV , c->defsv);
287 if (c->errsv) REPLACE_SV (ERRSV , c->errsv);
288
289 {
290 dSP;
291 CV *cv;
292
293 /* now do the ugly restore mess */
294 while ((cv = (CV *)POPs))
295 {
296 AV *padlist = (AV *)POPs;
297
298 if (padlist)
299 {
300 put_padlist (cv); /* mark this padlist as available */
301 CvPADLIST(cv) = padlist;
302 #ifdef USE_THREADS
303 /*CvOWNER(cv) = (struct perl_thread *)POPs;*/
304 #endif
305 }
306
307 ++CvDEPTH(cv);
308 }
309
310 PUTBACK;
311 }
312 }
313
314 static void
315 save_state(pTHX_ Coro__State c, int flags)
316 {
317 {
318 dSP;
319 I32 cxix = cxstack_ix;
320 PERL_CONTEXT *ccstk = cxstack;
321 PERL_SI *top_si = PL_curstackinfo;
322
323 /*
324 * the worst thing you can imagine happens first - we have to save
325 * (and reinitialize) all cv's in the whole callchain :(
326 */
327
328 PUSHs (Nullsv);
329 /* this loop was inspired by pp_caller */
330 for (;;)
331 {
332 do
333 {
334 PERL_CONTEXT *cx = &ccstk[cxix--];
335
336 if (CxTYPE(cx) == CXt_SUB)
337 {
338 CV *cv = cx->blk_sub.cv;
339 if (CvDEPTH(cv))
340 {
341 #ifdef USE_THREADS
342 /*XPUSHs ((SV *)CvOWNER(cv));*/
343 /*CvOWNER(cv) = 0;*/
344 /*error must unlock this cv etc.. etc...*/
345 #endif
346 EXTEND (SP, CvDEPTH(cv)*2);
347
348 while (--CvDEPTH(cv))
349 {
350 /* this tells the restore code to increment CvDEPTH */
351 PUSHs (Nullsv);
352 PUSHs ((SV *)cv);
353 }
354
355 PUSHs ((SV *)CvPADLIST(cv));
356 PUSHs ((SV *)cv);
357
358 get_padlist (cv); /* this is a monster */
359 }
360 }
361 else if (CxTYPE(cx) == CXt_FORMAT)
362 {
363 /* I never used formats, so how should I know how these are implemented? */
364 /* my bold guess is as a simple, plain sub... */
365 croak ("CXt_FORMAT not yet handled. Don't switch coroutines from within formats");
366 }
367 }
368 while (cxix >= 0);
369
370 if (top_si->si_type == PERLSI_MAIN)
371 break;
372
373 top_si = top_si->si_prev;
374 ccstk = top_si->si_cxstack;
375 cxix = top_si->si_cxix;
376 }
377
378 PUTBACK;
379 }
380
381 c->defav = flags & TRANSFER_SAVE_DEFAV ? (AV *)SvREFCNT_inc (GvAV (PL_defgv)) : 0;
382 c->defsv = flags & TRANSFER_SAVE_DEFSV ? SvREFCNT_inc (DEFSV) : 0;
383 c->errsv = flags & TRANSFER_SAVE_ERRSV ? SvREFCNT_inc (ERRSV) : 0;
384
385 /* I have not the slightest idea of why av_reify is necessary */
386 /* but if it's missing the defav contents magically get replaced sometimes */
387 if (c->defav)
388 av_reify (c->defav);
389
390 c->dowarn = PL_dowarn;
391
392 c->curstackinfo = PL_curstackinfo;
393 c->curstack = PL_curstack;
394 c->mainstack = PL_mainstack;
395 c->stack_sp = PL_stack_sp;
396 c->op = PL_op;
397 c->curpad = PL_curpad;
398 c->stack_base = PL_stack_base;
399 c->stack_max = PL_stack_max;
400 c->tmps_stack = PL_tmps_stack;
401 c->tmps_floor = PL_tmps_floor;
402 c->tmps_ix = PL_tmps_ix;
403 c->tmps_max = PL_tmps_max;
404 c->markstack = PL_markstack;
405 c->markstack_ptr = PL_markstack_ptr;
406 c->markstack_max = PL_markstack_max;
407 c->scopestack = PL_scopestack;
408 c->scopestack_ix = PL_scopestack_ix;
409 c->scopestack_max = PL_scopestack_max;
410 c->savestack = PL_savestack;
411 c->savestack_ix = PL_savestack_ix;
412 c->savestack_max = PL_savestack_max;
413 c->retstack = PL_retstack;
414 c->retstack_ix = PL_retstack_ix;
415 c->retstack_max = PL_retstack_max;
416 c->curcop = PL_curcop;
417 c->start_env = PL_start_env;
418 c->top_env = PL_top_env;
419 }
420
421 /*
422 * allocate various perl stacks. This is an exact copy
423 * of perl.c:init_stacks, except that it uses less memory
424 * on the assumption that coroutines do not usually need
425 * a lot of stackspace.
426 */
427 STATIC void
428 coro_init_stacks (pTHX)
429 {
430 PL_curstackinfo = new_stackinfo(96, 1024/sizeof(PERL_CONTEXT) - 1);
431 PL_curstackinfo->si_type = PERLSI_MAIN;
432 PL_curstack = PL_curstackinfo->si_stack;
433 PL_mainstack = PL_curstack; /* remember in case we switch stacks */
434
435 PL_stack_base = AvARRAY(PL_curstack);
436 PL_stack_sp = PL_stack_base;
437 PL_stack_max = PL_stack_base + AvMAX(PL_curstack);
438
439 New(50,PL_tmps_stack,64,SV*);
440 PL_tmps_floor = -1;
441 PL_tmps_ix = -1;
442 PL_tmps_max = 64;
443
444 New(54,PL_markstack,12,I32);
445 PL_markstack_ptr = PL_markstack;
446 PL_markstack_max = PL_markstack + 12;
447
448 SET_MARK_OFFSET;
449
450 New(54,PL_scopestack,12,I32);
451 PL_scopestack_ix = 0;
452 PL_scopestack_max = 12;
453
454 New(54,PL_savestack,64,ANY);
455 PL_savestack_ix = 0;
456 PL_savestack_max = 64;
457
458 New(54,PL_retstack,8,OP*);
459 PL_retstack_ix = 0;
460 PL_retstack_max = 8;
461 }
462
463 /*
464 * destroy the stacks, the callchain etc...
465 * still there is a memleak of 128 bytes...
466 */
467 STATIC void
468 destroy_stacks(pTHX)
469 {
470 /* is this ugly, I ask? */
471 while (PL_scopestack_ix)
472 LEAVE;
473
474 /* sure it is, but more important: is it correct?? :/ */
475 while (PL_tmps_ix > PL_tmps_floor) /* should only ever be one iteration */
476 FREETMPS;
477
478 while (PL_curstackinfo->si_next)
479 PL_curstackinfo = PL_curstackinfo->si_next;
480
481 while (PL_curstackinfo)
482 {
483 PERL_SI *p = PL_curstackinfo->si_prev;
484
485 {
486 dSP;
487 SWITCHSTACK (PL_curstack, PL_curstackinfo->si_stack);
488 PUTBACK; /* possibly superfluous */
489 }
490
491 dounwind(-1);
492
493 SvREFCNT_dec(PL_curstackinfo->si_stack);
494 Safefree(PL_curstackinfo->si_cxstack);
495 Safefree(PL_curstackinfo);
496 PL_curstackinfo = p;
497 }
498
499 Safefree(PL_tmps_stack);
500 Safefree(PL_markstack);
501 Safefree(PL_scopestack);
502 Safefree(PL_savestack);
503 Safefree(PL_retstack);
504 }
505
506 static void
507 allocate_stack (Coro__State ctx)
508 {
509 #ifdef HAVE_MMAP
510 ctx->ssize = 128 * 1024 * sizeof (long); /* mmap should do allocate-on-use */
511 ctx->sptr = mmap (0, ctx->ssize, PROT_EXEC|PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, 0, 0);
512 if (ctx->sptr == (void *)-1)
513 #endif
514 {
515 /*FIXME*//*D*//* reasonable stack size! */
516 ctx->ssize = 4096 * sizeof (long);
517 New (0, ctx->sptr, 4096, long);
518 }
519 }
520
521 static void
522 deallocate_stack (Coro__State ctx)
523 {
524 #ifdef HAVE_MMAP
525 munmap (ctx->sptr, ctx->ssize);
526 #else
527 Safefree (ctx->sptr);
528 #endif
529 }
530
531 /* might go away together with optional SAVE_CCTXT */
532 static void
533 setup_coro (void *arg)
534 {
535 /*
536 * emulate part of the perl startup here.
537 */
538 dSP;
539 Coro__State ctx = (Coro__State)arg;
540 SV *sub_init = (SV*)get_cv(SUB_INIT, FALSE);
541
542 coro_init_stacks (aTHX);
543 JMPENV_BOOTSTRAP;
544 SPAGAIN;
545
546 /*PL_curcop = 0;*/
547 SvREFCNT_dec (GvAV (PL_defgv));
548 GvAV (PL_defgv) = ctx->args;
549
550 if (ctx->sptr)
551 {
552 PUSHMARK(SP);
553 PUTBACK;
554 (void) call_sv (sub_init, G_VOID|G_NOARGS);
555 croak ("FATAL: CCTXT coroutine returned!");
556 }
557 else
558 {
559 UNOP myop;
560
561 PL_op = (OP *)&myop;
562
563 Zero(&myop, 1, UNOP);
564 myop.op_next = Nullop;
565 myop.op_flags = OPf_WANT_VOID;
566
567 PUSHMARK(SP);
568 XPUSHs (sub_init);
569 /*
570 * the next line is slightly wrong, as PL_op->op_next
571 * is actually being executed so we skip the first op.
572 * that doesn't matter, though, since it is only
573 * pp_nextstate and we never return...
574 * ah yes, and I don't care anyways ;)
575 */
576 PUTBACK;
577 PL_op = pp_entersub();
578 SPAGAIN;
579
580 ENTER; /* necessary e.g. for dounwind */
581 }
582 }
583
584 STATIC void
585 transfer(pTHX_ struct coro *prev, struct coro *next, int flags)
586 {
587 dSP;
588
589 if (prev != next)
590 {
591 /*
592 * this could be done in newprocess which would lead to
593 * extremely elegant and fast (basically just SAVE/LOAD)
594 * code here, but lazy allocation of stacks has also
595 * some virtues and the overhead of the if() is nil.
596 */
597 if (next->mainstack)
598 {
599 SAVE (prev, flags);
600 LOAD (next);
601
602 /* mark this state as in-use */
603 next->mainstack = 0;
604 next->tmps_ix = -2;
605
606 if (flags & TRANSFER_SAVE_CCTXT)
607 {
608 if (!next->ssize)
609 croak ("destination coroutine has no CCTXT (%p, %d)", next->sptr, next->ssize);
610
611 if (!prev->ssize)
612 prev->ssize = 1; /* mark cctx as valid ;) */
613
614 coro_transfer (&(prev->cctx), &(next->cctx));
615 }
616
617 }
618 else if (next->tmps_ix == -2)
619 croak ("tried to transfer to running coroutine");
620 else
621 {
622 SAVE (prev, -1); /* first get rid of the old state */
623
624 if (flags & TRANSFER_SAVE_CCTXT)
625 {
626 if (!next->ssize)
627 {
628 allocate_stack (next);
629 coro_create (&(next->cctx),
630 setup_coro, (void *)next,
631 next->sptr, next->ssize);
632 }
633
634 if (!prev->ssize)
635 prev->ssize = 1; /* mark cctx as valid ;) */
636
637 coro_transfer (&(prev->cctx), &(next->cctx));
638 }
639 else
640 setup_coro (next);
641 }
642 }
643 }
644
645 MODULE = Coro::State PACKAGE = Coro::State
646
647 PROTOTYPES: ENABLE
648
649 BOOT:
650 { /* {} necessary for stoopid perl-5.6.x */
651 coro_state_stash = gv_stashpvn ("Coro::State", 10, TRUE);
652
653 newCONSTSUB (coro_state_stash, "SAVE_DEFAV", newSViv (TRANSFER_SAVE_DEFAV));
654 newCONSTSUB (coro_state_stash, "SAVE_DEFSV", newSViv (TRANSFER_SAVE_DEFSV));
655 newCONSTSUB (coro_state_stash, "SAVE_ERRSV", newSViv (TRANSFER_SAVE_ERRSV));
656 newCONSTSUB (coro_state_stash, "SAVE_CCTXT", newSViv (TRANSFER_SAVE_CCTXT));
657
658 if (!padlist_cache)
659 padlist_cache = newHV ();
660
661 main_mainstack = PL_mainstack;
662 }
663
664 Coro::State
665 _newprocess(args)
666 SV * args
667 PROTOTYPE: $
668 CODE:
669 Coro__State coro;
670
671 if (!SvROK (args) || SvTYPE (SvRV (args)) != SVt_PVAV)
672 croak ("Coro::State::_newprocess expects an arrayref");
673
674 New (0, coro, 1, struct coro);
675
676 coro->args = (AV *)SvREFCNT_inc (SvRV (args));
677 coro->mainstack = 0; /* actual work is done inside transfer */
678 coro->sptr = 0;
679 coro->ssize = 0;
680
681 RETVAL = coro;
682 OUTPUT:
683 RETVAL
684
685 void
686 transfer(prev, next, flags = TRANSFER_SAVE_ALL)
687 Coro::State_or_hashref prev
688 Coro::State_or_hashref next
689 int flags
690 PROTOTYPE: @
691 CODE:
692 transfer (aTHX_ prev, next, flags);
693
694 void
695 DESTROY(coro)
696 Coro::State coro
697 CODE:
698
699 if (coro->mainstack && coro->mainstack != main_mainstack)
700 {
701 struct coro temp;
702
703 SAVE(aTHX_ (&temp), TRANSFER_SAVE_ALL);
704 LOAD(aTHX_ coro);
705
706 destroy_stacks (aTHX);
707
708 LOAD((&temp)); /* this will get rid of defsv etc.. */
709
710 coro->mainstack = 0;
711 }
712
713 if (coro->sptr)
714 {
715 deallocate_stack (coro);
716 coro->sptr = 0;
717 }
718
719 Safefree (coro);
720
721 void
722 flush()
723 CODE:
724 #ifdef MAY_FLUSH
725 flush_padlist_cache ();
726 #endif
727
728 MODULE = Coro::State PACKAGE = Coro::Cont
729
730 # this is slightly dirty
731
732 void
733 yield(...)
734 PROTOTYPE: @
735 CODE:
736 static SV *returnstk;
737 SV *sv;
738 AV *defav = GvAV (PL_defgv);
739 struct coro *prev, *next;
740
741 if (!returnstk)
742 returnstk = SvRV (get_sv ("Coro::Cont::return", FALSE));
743
744 /* set up @_ -- ugly */
745 av_clear (defav);
746 av_fill (defav, items - 1);
747 while (items--)
748 av_store (defav, items, SvREFCNT_inc (ST(items)));
749
750 mg_get (returnstk); /* isn't documentation wrong for mg_get? */
751 sv = av_pop ((AV *)SvRV (returnstk));
752 prev = (struct coro *)SvIV ((SV*)SvRV (*av_fetch ((AV *)SvRV (sv), 0, 0)));
753 next = (struct coro *)SvIV ((SV*)SvRV (*av_fetch ((AV *)SvRV (sv), 1, 0)));
754 SvREFCNT_dec (sv);
755
756 transfer(aTHX_ prev, next, 0);
757