universal.c

   1 /*    universal.c
   2  *
   3  *    Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   4  *    2005, by Larry Wall and others
   5  *
   6  *    You may distribute under the terms of either the GNU General Public
   7  *    License or the Artistic License, as specified in the README file.
   8  *
   9  */
  10
  11 /*
  12  * "The roots of those mountains must be roots indeed; there must be
  13  * great secrets buried there which have not been discovered since the
  14  * beginning." --Gandalf, relating Gollum's story
  15  */
  16
  17 /* This file contains the code that implements the functions in Perl's
  18  * UNIVERSAL package, such as UNIVERSAL->can().
  19  */
  20
  21 #include "EXTERN.h"
  22 #define PERL_IN_UNIVERSAL_C
  23 #include "perl.h"
  24
  25 #ifdef USE_PERLIO
  26 #include "perliol.h" /* For the PERLIO_F_XXX */
  27 #endif
  28
  29 /*
  30  * Contributed by Graham Barr  <Graham.Barr@tiuk.ti.com>
  31  * The main guts of traverse_isa was actually copied from gv_fetchmeth
  32  */
  33
  34 STATIC SV *
  35 S_isa_lookup(pTHX_ HV *stash, const char *name, HV* name_stash,
  36              int len, int level)
  37 {
  38     AV* av;
  39     GV* gv;
  40     GV** gvp;
  41     HV* hv = Nullhv;
  42     SV* subgen = Nullsv;
  43     const char *hvname;
  44
  45     /* A stash/class can go by many names (ie. User == main::User), so
  46        we compare the stash itself just in case */
  47     if (name_stash && (stash == name_stash))
  48         return &PL_sv_yes;
  49
  50     hvname = HvNAME_get(stash);
  51
  52     if (strEQ(hvname, name))
  53         return &PL_sv_yes;
  54
  55     if (strEQ(name, "UNIVERSAL"))
  56         return &PL_sv_yes;
  57
  58     if (level > 100)
  59         Perl_croak(aTHX_ "Recursive inheritance detected in package '%s'",
  60                    hvname);
  61
  62     gvp = (GV**)hv_fetch(stash, "::ISA::CACHE::", 14, FALSE);
  63
  64     if (gvp && (gv = *gvp) != (GV*)&PL_sv_undef && (subgen = GvSV(gv))
  65         && (hv = GvHV(gv)))
  66     {
  67         if (SvIV(subgen) == (IV)PL_sub_generation) {
  68             SV* sv;
  69             SV** svp = (SV**)hv_fetch(hv, name, len, FALSE);
  70             if (svp && (sv = *svp) != (SV*)&PL_sv_undef) {
  71                 DEBUG_o( Perl_deb(aTHX_ "Using cached ISA %s for package %s\n",
  72                                   name, hvname) );
  73                 return sv;
  74             }
  75         }
  76         else {
  77             DEBUG_o( Perl_deb(aTHX_ "ISA Cache in package %s is stale\n",
  78                               hvname) );
  79             hv_clear(hv);
  80             sv_setiv(subgen, PL_sub_generation);
  81         }
  82     }
  83
  84     gvp = (GV**)hv_fetch(stash,"ISA",3,FALSE);
  85
  86     if (gvp && (gv = *gvp) != (GV*)&PL_sv_undef && (av = GvAV(gv))) {
  87         if (!hv || !subgen) {
  88             gvp = (GV**)hv_fetch(stash, "::ISA::CACHE::", 14, TRUE);
  89
  90             gv = *gvp;
  91
  92             if (SvTYPE(gv) != SVt_PVGV)
  93                 gv_init(gv, stash, "::ISA::CACHE::", 14, TRUE);
  94
  95             if (!hv)
  96                 hv = GvHVn(gv);
  97             if (!subgen) {
  98                 subgen = newSViv(PL_sub_generation);
  99                 GvSV(gv) = subgen;
 100             }
 101         }
 102         if (hv) {
 103             SV** svp = AvARRAY(av);
 104             /* NOTE: No support for tied ISA */
 105             I32 items = AvFILLp(av) + 1;
 106             while (items--) {
 107                 SV* sv = *svp++;
 108                 HV* basestash = gv_stashsv(sv, FALSE);
 109                 if (!basestash) {
 110                     if (ckWARN(WARN_MISC))
 111                         Perl_warner(aTHX_ packWARN(WARN_SYNTAX),
 112                                     "Can't locate package %"SVf" for @%s::ISA",
 113                                     sv, hvname);
 114                     continue;
 115                 }
 116                 if (&PL_sv_yes == isa_lookup(basestash, name, name_stash,
 117                                              len, level + 1)) {
 118                     (void)hv_store(hv,name,len,&PL_sv_yes,0);
 119                     return &PL_sv_yes;
 120                 }
 121             }
 122             (void)hv_store(hv,name,len,&PL_sv_no,0);
 123         }
 124     }
 125     return &PL_sv_no;
 126 }
 127
 128 /*
 129 =head1 SV Manipulation Functions
 130
 131 =for apidoc sv_derived_from
 132
 133 Returns a boolean indicating whether the SV is derived from the specified
 134 class.  This is the function that implements C<UNIVERSAL::isa>.  It works
 135 for class names as well as for objects.
 136
 137 =cut
 138 */
 139
 140 bool
 141 Perl_sv_derived_from(pTHX_ SV *sv, const char *name)
 142 {
 143     const char *type = Nullch;
 144     HV *stash = Nullhv;
 145     HV *name_stash;
 146
 147     if (SvGMAGICAL(sv))
 148         mg_get(sv) ;
 149
 150     if (SvROK(sv)) {
 151         sv = SvRV(sv);
 152         type = sv_reftype(sv,0);
 153         if (SvOBJECT(sv))
 154             stash = SvSTASH(sv);
 155     }
 156     else {
 157         stash = gv_stashsv(sv, FALSE);
 158     }
 159
 160     name_stash = gv_stashpv(name, FALSE);
 161
 162     return (type && strEQ(type,name)) ||
 163             (stash && isa_lookup(stash, name, name_stash, strlen(name), 0)
 164              == &PL_sv_yes)
 165         ? TRUE
 166         : FALSE ;
 167 }
 168
 169 #include "XSUB.h"
 170
 171 PERL_XS_EXPORT_C void XS_UNIVERSAL_isa(pTHX_ CV *cv);
 172 PERL_XS_EXPORT_C void XS_UNIVERSAL_can(pTHX_ CV *cv);
 173 PERL_XS_EXPORT_C void XS_UNIVERSAL_VERSION(pTHX_ CV *cv);
 174 XS(XS_version_new);
 175 XS(XS_version_stringify);
 176 XS(XS_version_numify);
 177 XS(XS_version_vcmp);
 178 XS(XS_version_boolean);
 179 #ifdef HASATTRIBUTE_NORETURN
 180 XS(XS_version_noop) __attribute__noreturn__;
 181 #else
 182 XS(XS_version_noop);
 183 #endif
 184 XS(XS_version_is_alpha);
 185 XS(XS_version_qv);
 186 XS(XS_utf8_is_utf8);
 187 XS(XS_utf8_valid);
 188 XS(XS_utf8_encode);
 189 XS(XS_utf8_decode);
 190 XS(XS_utf8_upgrade);
 191 XS(XS_utf8_downgrade);
 192 XS(XS_utf8_unicode_to_native);
 193 XS(XS_utf8_native_to_unicode);
 194 XS(XS_Internals_SvREADONLY);
 195 XS(XS_Internals_SvREFCNT);
 196 XS(XS_Internals_hv_clear_placehold);
 197 XS(XS_PerlIO_get_layers);
 198 XS(XS_Regexp_DESTROY);
 199 XS(XS_Internals_hash_seed);
 200 XS(XS_Internals_rehash_seed);
 201 XS(XS_Internals_HvREHASH);
 202
 203 void
 204 Perl_boot_core_UNIVERSAL(pTHX)
 205 {
 206     const char file[] = __FILE__;
 207
 208     newXS("UNIVERSAL::isa",             XS_UNIVERSAL_isa,         file);
 209     newXS("UNIVERSAL::can",             XS_UNIVERSAL_can,         file);
 210     newXS("UNIVERSAL::VERSION",         XS_UNIVERSAL_VERSION,     file);
 211     {
 212         /* register the overloading (type 'A') magic */
 213         PL_amagic_generation++;
 214         /* Make it findable via fetchmethod */
 215         newXS("version::()", XS_version_noop, file);
 216         newXS("version::new", XS_version_new, file);
 217         newXS("version::(\"\"", XS_version_stringify, file);
 218         newXS("version::stringify", XS_version_stringify, file);
 219         newXS("version::(0+", XS_version_numify, file);
 220         newXS("version::numify", XS_version_numify, file);
 221         newXS("version::(cmp", XS_version_vcmp, file);
 222         newXS("version::(<=>", XS_version_vcmp, file);
 223         newXS("version::vcmp", XS_version_vcmp, file);
 224         newXS("version::(bool", XS_version_boolean, file);
 225         newXS("version::boolean", XS_version_boolean, file);
 226         newXS("version::(nomethod", XS_version_noop, file);
 227         newXS("version::noop", XS_version_noop, file);
 228         newXS("version::is_alpha", XS_version_is_alpha, file);
 229         newXS("version::qv", XS_version_qv, file);
 230     }
 231     newXS("utf8::is_utf8", XS_utf8_is_utf8, file);
 232     newXS("utf8::valid", XS_utf8_valid, file);
 233     newXS("utf8::encode", XS_utf8_encode, file);
 234     newXS("utf8::decode", XS_utf8_decode, file);
 235     newXS("utf8::upgrade", XS_utf8_upgrade, file);
 236     newXS("utf8::downgrade", XS_utf8_downgrade, file);
 237     newXS("utf8::native_to_unicode", XS_utf8_native_to_unicode, file);
 238     newXS("utf8::unicode_to_native", XS_utf8_unicode_to_native, file);
 239     newXSproto("Internals::SvREADONLY",XS_Internals_SvREADONLY, file, "\\[$%@];$");
 240     newXSproto("Internals::SvREFCNT",XS_Internals_SvREFCNT, file, "\\[$%@];$");
 241     newXSproto("Internals::hv_clear_placeholders",
 242                XS_Internals_hv_clear_placehold, file, "\\%");
 243     newXSproto("PerlIO::get_layers",
 244                XS_PerlIO_get_layers, file, "*;@");
 245     newXS("Regexp::DESTROY", XS_Regexp_DESTROY, file);
 246     newXSproto("Internals::hash_seed",XS_Internals_hash_seed, file, "");
 247     newXSproto("Internals::rehash_seed",XS_Internals_rehash_seed, file, "");
 248     newXSproto("Internals::HvREHASH", XS_Internals_HvREHASH, file, "\\%");
 249 }
 250
 251
 252 XS(XS_UNIVERSAL_isa)
 253 {
 254     dXSARGS;
 255     SV *sv;
 256     const char *name;
 257
 258     if (items != 2)
 259         Perl_croak(aTHX_ "Usage: UNIVERSAL::isa(reference, kind)");
 260
 261     sv = ST(0);
 262
 263     if (SvGMAGICAL(sv))
 264         mg_get(sv);
 265
 266     if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))
 267                 || (SvGMAGICAL(sv) && SvPOKp(sv) && SvCUR(sv))))
 268         XSRETURN_UNDEF;
 269
 270     name = SvPV_nolen_const(ST(1));
 271
 272     ST(0) = boolSV(sv_derived_from(sv, name));
 273     XSRETURN(1);
 274 }
 275
 276 XS(XS_UNIVERSAL_can)
 277 {
 278     dXSARGS;
 279     SV   *sv;
 280     const char *name;
 281     SV   *rv;
 282     HV   *pkg = NULL;
 283
 284     if (items != 2)
 285         Perl_croak(aTHX_ "Usage: UNIVERSAL::can(object-ref, method)");
 286
 287     sv = ST(0);
 288
 289     if (SvGMAGICAL(sv))
 290         mg_get(sv);
 291
 292     if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))
 293                 || (SvGMAGICAL(sv) && SvPOKp(sv) && SvCUR(sv))))
 294         XSRETURN_UNDEF;
 295
 296     name = SvPV_nolen_const(ST(1));
 297     rv = &PL_sv_undef;
 298
 299     if (SvROK(sv)) {
 300         sv = (SV*)SvRV(sv);
 301         if (SvOBJECT(sv))
 302             pkg = SvSTASH(sv);
 303     }
 304     else {
 305         pkg = gv_stashsv(sv, FALSE);
 306     }
 307
 308     if (pkg) {
 309         GV *gv = gv_fetchmethod_autoload(pkg, name, FALSE);
 310         if (gv && isGV(gv))
 311             rv = sv_2mortal(newRV((SV*)GvCV(gv)));
 312     }
 313
 314     ST(0) = rv;
 315     XSRETURN(1);
 316 }
 317
 318 XS(XS_UNIVERSAL_VERSION)
 319 {
 320     dXSARGS;
 321     HV *pkg;
 322     GV **gvp;
 323     GV *gv;
 324     SV *sv;
 325     const char *undef;
 326
 327     if (SvROK(ST(0))) {
 328         sv = (SV*)SvRV(ST(0));
 329         if (!SvOBJECT(sv))
 330             Perl_croak(aTHX_ "Cannot find version of an unblessed reference");
 331         pkg = SvSTASH(sv);
 332     }
 333     else {
 334         pkg = gv_stashsv(ST(0), FALSE);
 335     }
 336
 337     gvp = pkg ? (GV**)hv_fetch(pkg,"VERSION",7,FALSE) : Null(GV**);
 338
 339     if (gvp && isGV(gv = *gvp) && SvOK(sv = GvSV(gv))) {
 340         SV *nsv = sv_newmortal();
 341         sv_setsv(nsv, sv);
 342         sv = nsv;
 343         if ( !sv_derived_from(sv, "version"))
 344             upg_version(sv);
 345         undef = Nullch;
 346     }
 347     else {
 348         sv = (SV*)&PL_sv_undef;
 349         undef = "(undef)";
 350     }
 351
 352     if (items > 1) {
 353         SV *req = ST(1);
 354
 355         if (undef) {
 356             if (pkg) {
 357                 const char *name = HvNAME_get(pkg);
 358                 Perl_croak(aTHX_
 359                            "%s does not define $%s::VERSION--version check failed",
 360                            name, name);
 361             } else {
 362                 Perl_croak(aTHX_
 363                              "%s defines neither package nor VERSION--version check failed",
 364                              SvPVx_nolen_const(ST(0)) );
 365              }
 366         }
 367
 368         if ( !sv_derived_from(req, "version")) {
 369             /* req may very well be R/O, so create a new object */
 370             SV *nsv = sv_newmortal();
 371             sv_setsv(nsv, req);
 372             req = nsv;
 373             upg_version(req);
 374         }
 375
 376         if ( vcmp( req, sv ) > 0 )
 377             Perl_croak(aTHX_ "%s version %"SVf" (%"SVf") required--"
 378                     "this is only version %"SVf" (%"SVf")", HvNAME_get(pkg),
 379                     vnumify(req),vnormal(req),vnumify(sv),vnormal(sv));
 380     }
 381
 382     if ( SvOK(sv) && sv_derived_from(sv, "version") ) {
 383         ST(0) = vnumify(sv);
 384     } else {
 385         ST(0) = sv;
 386     }
 387
 388     XSRETURN(1);
 389 }
 390
 391 XS(XS_version_new)
 392 {
 393     dXSARGS;
 394     if (items > 3)
 395         Perl_croak(aTHX_ "Usage: version::new(class, version)");
 396     SP -= items;
 397     {
 398         const char *classname = SvPV_nolen(ST(0));
 399         SV *vs = ST(1);
 400         SV *rv;
 401         if (items == 3 )
 402         {
 403             vs = sv_newmortal();
 404             Perl_sv_setpvf(aTHX_ vs,"v%s",SvPV_nolen(ST(2)));
 405         }
 406
 407         rv = new_version(vs);
 408         if ( strcmp(classname,"version") != 0 ) /* inherited new() */
 409             sv_bless(rv, gv_stashpv(classname,TRUE));
 410
 411         PUSHs(sv_2mortal(rv));
 412         PUTBACK;
 413         return;
 414     }
 415 }
 416
 417 XS(XS_version_stringify)
 418 {
 419      dXSARGS;
 420      if (items < 1)
 421           Perl_croak(aTHX_ "Usage: version::stringify(lobj, ...)");
 422      SP -= items;
 423      {
 424           SV *  lobj = Nullsv;
 425
 426           if (sv_derived_from(ST(0), "version")) {
 427                SV *tmp = SvRV(ST(0));
 428                lobj = tmp;
 429           }
 430           else
 431                Perl_croak(aTHX_ "lobj is not of type version");
 432
 433           PUSHs(sv_2mortal(vstringify(lobj)));
 434
 435           PUTBACK;
 436           return;
 437      }
 438 }
 439
 440 XS(XS_version_numify)
 441 {
 442      dXSARGS;
 443      if (items < 1)
 444           Perl_croak(aTHX_ "Usage: version::numify(lobj, ...)");
 445      SP -= items;
 446      {
 447           SV *  lobj = Nullsv;
 448
 449           if (sv_derived_from(ST(0), "version")) {
 450                SV *tmp = SvRV(ST(0));
 451                lobj = tmp;
 452           }
 453           else
 454                Perl_croak(aTHX_ "lobj is not of type version");
 455
 456           PUSHs(sv_2mortal(vnumify(lobj)));
 457
 458           PUTBACK;
 459           return;
 460      }
 461 }
 462
 463 XS(XS_version_vcmp)
 464 {
 465      dXSARGS;
 466      if (items < 1)
 467           Perl_croak(aTHX_ "Usage: version::vcmp(lobj, ...)");
 468      SP -= items;
 469      {
 470           SV *  lobj = Nullsv;
 471
 472           if (sv_derived_from(ST(0), "version")) {
 473                SV *tmp = SvRV(ST(0));
 474                lobj = tmp;
 475           }
 476           else
 477                Perl_croak(aTHX_ "lobj is not of type version");
 478
 479           {
 480                SV       *rs;
 481                SV       *rvs;
 482                SV * robj = ST(1);
 483                IV        swap = (IV)SvIV(ST(2));
 484
 485                if ( ! sv_derived_from(robj, "version") )
 486                {
 487                     robj = new_version(robj);
 488                }
 489                rvs = SvRV(robj);
 490
 491                if ( swap )
 492                {
 493                     rs = newSViv(vcmp(rvs,lobj));
 494                }
 495                else
 496                {
 497                     rs = newSViv(vcmp(lobj,rvs));
 498                }
 499
 500                PUSHs(sv_2mortal(rs));
 501           }
 502
 503           PUTBACK;
 504           return;
 505      }
 506 }
 507
 508 XS(XS_version_boolean)
 509 {
 510      dXSARGS;
 511      if (items < 1)
 512           Perl_croak(aTHX_ "Usage: version::boolean(lobj, ...)");
 513      SP -= items;
 514      {
 515           SV *  lobj = Nullsv;
 516
 517           if (sv_derived_from(ST(0), "version")) {
 518                /* XXX If tmp serves a purpose, explain it. */
 519                SV *tmp = SvRV(ST(0));
 520                lobj = tmp;
 521           }
 522           else
 523                Perl_croak(aTHX_ "lobj is not of type version");
 524
 525           {
 526                SV       *rs;
 527                rs = newSViv( vcmp(lobj,new_version(newSVpvn("0",1))) );
 528                PUSHs(sv_2mortal(rs));
 529           }
 530
 531           PUTBACK;
 532           return;
 533      }
 534 }
 535
 536 XS(XS_version_noop)
 537 {
 538     dXSARGS;
 539     if (items < 1)
 540         Perl_croak(aTHX_ "Usage: version::noop(lobj, ...)");
 541     if (sv_derived_from(ST(0), "version"))
 542         Perl_croak(aTHX_ "operation not supported with version object");
 543     else
 544         Perl_croak(aTHX_ "lobj is not of type version");
 545 #ifndef HASATTRIBUTE_NORETURN
 546     XSRETURN_EMPTY;
 547 #endif
 548 }
 549
 550 XS(XS_version_is_alpha)
 551 {
 552     dXSARGS;
 553     if (items != 1)
 554         Perl_croak(aTHX_ "Usage: version::is_alpha(lobj)");
 555     SP -= items;
 556     {
 557         SV * lobj = Nullsv;
 558
 559         if (sv_derived_from(ST(0), "version")) {
 560                 /* XXX If tmp serves a purpose, explain it. */
 561                 SV *tmp = SvRV(ST(0));
 562                 lobj = tmp;
 563         }
 564         else
 565                 Perl_croak(aTHX_ "lobj is not of type version");
 566 {
 567     const I32 len = av_len((AV *)lobj);
 568     const I32 digit = SvIVX(*av_fetch((AV *)lobj, len, 0));
 569     if ( digit < 0 )
 570         XSRETURN_YES;
 571     else
 572         XSRETURN_NO;
 573 }
 574         PUTBACK;
 575         return;
 576     }
 577 }
 578
 579 XS(XS_version_qv)
 580 {
 581     dXSARGS;
 582     if (items != 1)
 583         Perl_croak(aTHX_ "Usage: version::qv(ver)");
 584     SP -= items;
 585     {
 586         SV *    ver = ST(0);
 587         if ( !SvVOK(ver) ) /* only need to do with if not already v-string */
 588         {
 589             SV *vs = sv_newmortal();
 590             char *version;
 591             if ( SvNOK(ver) ) /* may get too much accuracy */
 592             {
 593                 char tbuf[64];
 594                 sprintf(tbuf,"%.9"NVgf, SvNVX(ver));
 595                 version = savepv(tbuf);
 596             }
 597             else
 598             {
 599                 version = savesvpv(ver);
 600             }
 601             (void)scan_version(version,vs,TRUE);
 602             Safefree(version);
 603
 604             PUSHs(vs);
 605         }
 606         else
 607         {
 608             PUSHs(sv_2mortal(new_version(ver)));
 609         }
 610
 611         PUTBACK;
 612         return;
 613     }
 614 }
 615
 616 XS(XS_utf8_is_utf8)
 617 {
 618      dXSARGS;
 619      if (items != 1)
 620           Perl_croak(aTHX_ "Usage: utf8::is_utf8(sv)");
 621      {
 622           const SV *sv = ST(0);
 623           {
 624                if (SvUTF8(sv))
 625                     XSRETURN_YES;
 626                else
 627                     XSRETURN_NO;
 628           }
 629      }
 630      XSRETURN_EMPTY;
 631 }
 632
 633 XS(XS_utf8_valid)
 634 {
 635      dXSARGS;
 636      if (items != 1)
 637           Perl_croak(aTHX_ "Usage: utf8::valid(sv)");
 638      {
 639           SV *  sv = ST(0);
 640           {
 641                STRLEN len;
 642                const char *s = SvPV_const(sv,len);
 643                if (!SvUTF8(sv) || is_utf8_string((const U8*)s,len))
 644                     XSRETURN_YES;
 645                else
 646                     XSRETURN_NO;
 647           }
 648      }
 649      XSRETURN_EMPTY;
 650 }
 651
 652 XS(XS_utf8_encode)
 653 {
 654     dXSARGS;
 655     if (items != 1)
 656         Perl_croak(aTHX_ "Usage: utf8::encode(sv)");
 657     {
 658         SV *    sv = ST(0);
 659
 660         sv_utf8_encode(sv);
 661     }
 662     XSRETURN_EMPTY;
 663 }
 664
 665 XS(XS_utf8_decode)
 666 {
 667     dXSARGS;
 668     if (items != 1)
 669         Perl_croak(aTHX_ "Usage: utf8::decode(sv)");
 670     {
 671         SV *    sv = ST(0);
 672         const bool RETVAL = sv_utf8_decode(sv);
 673         ST(0) = boolSV(RETVAL);
 674         sv_2mortal(ST(0));
 675     }
 676     XSRETURN(1);
 677 }
 678
 679 XS(XS_utf8_upgrade)
 680 {
 681     dXSARGS;
 682     if (items != 1)
 683         Perl_croak(aTHX_ "Usage: utf8::upgrade(sv)");
 684     {
 685         SV *    sv = ST(0);
 686         STRLEN  RETVAL;
 687         dXSTARG;
 688
 689         RETVAL = sv_utf8_upgrade(sv);
 690         XSprePUSH; PUSHi((IV)RETVAL);
 691     }
 692     XSRETURN(1);
 693 }
 694
 695 XS(XS_utf8_downgrade)
 696 {
 697     dXSARGS;
 698     if (items < 1 || items > 2)
 699         Perl_croak(aTHX_ "Usage: utf8::downgrade(sv, failok=0)");
 700     {
 701         SV *    sv = ST(0);
 702         const bool failok = (items < 2) ? 0 : (int)SvIV(ST(1));
 703         const bool RETVAL = sv_utf8_downgrade(sv, failok);
 704
 705         ST(0) = boolSV(RETVAL);
 706         sv_2mortal(ST(0));
 707     }
 708     XSRETURN(1);
 709 }
 710
 711 XS(XS_utf8_native_to_unicode)
 712 {
 713  dXSARGS;
 714  const UV uv = SvUV(ST(0));
 715
 716  if (items > 1)
 717      Perl_croak(aTHX_ "Usage: utf8::native_to_unicode(sv)");
 718
 719  ST(0) = sv_2mortal(newSViv(NATIVE_TO_UNI(uv)));
 720  XSRETURN(1);
 721 }
 722
 723 XS(XS_utf8_unicode_to_native)
 724 {
 725  dXSARGS;
 726  const UV uv = SvUV(ST(0));
 727
 728  if (items > 1)
 729      Perl_croak(aTHX_ "Usage: utf8::unicode_to_native(sv)");
 730
 731  ST(0) = sv_2mortal(newSViv(UNI_TO_NATIVE(uv)));
 732  XSRETURN(1);
 733 }
 734
 735 XS(XS_Internals_SvREADONLY)     /* This is dangerous stuff. */
 736 {
 737     dXSARGS;
 738     SV *sv = SvRV(ST(0));
 739
 740     if (items == 1) {
 741          if (SvREADONLY(sv))
 742              XSRETURN_YES;
 743          else
 744              XSRETURN_NO;
 745     }
 746     else if (items == 2) {
 747         if (SvTRUE(ST(1))) {
 748             SvREADONLY_on(sv);
 749             XSRETURN_YES;
 750         }
 751         else {
 752             /* I hope you really know what you are doing. */
 753             SvREADONLY_off(sv);
 754             XSRETURN_NO;
 755         }
 756     }
 757     XSRETURN_UNDEF; /* Can't happen. */
 758 }
 759
 760 XS(XS_Internals_SvREFCNT)       /* This is dangerous stuff. */
 761 {
 762     dXSARGS;
 763     SV *sv = SvRV(ST(0));
 764
 765     if (items == 1)
 766          XSRETURN_IV(SvREFCNT(sv) - 1); /* Minus the ref created for us. */
 767     else if (items == 2) {
 768          /* I hope you really know what you are doing. */
 769          SvREFCNT(sv) = SvIV(ST(1));
 770          XSRETURN_IV(SvREFCNT(sv));
 771     }
 772     XSRETURN_UNDEF; /* Can't happen. */
 773 }
 774
 775 XS(XS_Internals_hv_clear_placehold)
 776 {
 777     dXSARGS;
 778     HV *hv = (HV *) SvRV(ST(0));
 779
 780     if (items != 1)
 781         Perl_croak(aTHX_ "Usage: UNIVERSAL::hv_clear_placeholders(hv)");
 782     hv_clear_placeholders(hv);
 783     XSRETURN(0);
 784 }
 785
 786 XS(XS_Regexp_DESTROY)
 787 {
 788 }
 789
 790 XS(XS_PerlIO_get_layers)
 791 {
 792     dXSARGS;
 793     if (items < 1 || items % 2 == 0)
 794         Perl_croak(aTHX_ "Usage: PerlIO_get_layers(filehandle[,args])");
 795 #ifdef USE_PERLIO
 796     {
 797         SV *    sv;
 798         GV *    gv;
 799         IO *    io;
 800         bool    input = TRUE;
 801         bool    details = FALSE;
 802
 803         if (items > 1) {
 804              SV **svp;
 805
 806              for (svp = MARK + 2; svp <= SP; svp += 2) {
 807                   SV **varp = svp;
 808                   SV **valp = svp + 1;
 809                   STRLEN klen;
 810                   const char *key = SvPV_const(*varp, klen);
 811
 812                   switch (*key) {
 813                   case 'i':
 814                        if (klen == 5 && memEQ(key, "input", 5)) {
 815                             input = SvTRUE(*valp);
 816                             break;
 817                        }
 818                        goto fail;
 819                   case 'o':
 820                        if (klen == 6 && memEQ(key, "output", 6)) {
 821                             input = !SvTRUE(*valp);
 822                             break;
 823                        }
 824                        goto fail;
 825                   case 'd':
 826                        if (klen == 7 && memEQ(key, "details", 7)) {
 827                             details = SvTRUE(*valp);
 828                             break;
 829                        }
 830                        goto fail;
 831                   default:
 832                   fail:
 833                        Perl_croak(aTHX_
 834                                   "get_layers: unknown argument '%s'",
 835                                   key);
 836                   }
 837              }
 838
 839              SP -= (items - 1);
 840         }
 841
 842         sv = POPs;
 843         gv = (GV*)sv;
 844
 845         if (!isGV(sv)) {
 846              if (SvROK(sv) && isGV(SvRV(sv)))
 847                   gv = (GV*)SvRV(sv);
 848              else
 849                   gv = gv_fetchsv(sv, FALSE, SVt_PVIO);
 850         }
 851
 852         if (gv && (io = GvIO(gv))) {
 853              dTARGET;
 854              AV* av = PerlIO_get_layers(aTHX_ input ?
 855                                         IoIFP(io) : IoOFP(io));
 856              I32 i;
 857              I32 last = av_len(av);
 858              I32 nitem = 0;
 859
 860              for (i = last; i >= 0; i -= 3) {
 861                   SV **namsvp;
 862                   SV **argsvp;
 863                   SV **flgsvp;
 864                   bool namok, argok, flgok;
 865
 866                   namsvp = av_fetch(av, i - 2, FALSE);
 867                   argsvp = av_fetch(av, i - 1, FALSE);
 868                   flgsvp = av_fetch(av, i,     FALSE);
 869
 870                   namok = namsvp && *namsvp && SvPOK(*namsvp);
 871                   argok = argsvp && *argsvp && SvPOK(*argsvp);
 872                   flgok = flgsvp && *flgsvp && SvIOK(*flgsvp);
 873
 874                   if (details) {
 875                        XPUSHs(namok ?
 876                              newSVpv(SvPVX_const(*namsvp), 0) : &PL_sv_undef);
 877                        XPUSHs(argok ?
 878                              newSVpv(SvPVX_const(*argsvp), 0) : &PL_sv_undef);
 879                        if (flgok)
 880                             XPUSHi(SvIVX(*flgsvp));
 881                        else
 882                             XPUSHs(&PL_sv_undef);
 883                        nitem += 3;
 884                   }
 885                   else {
 886                        if (namok && argok)
 887                             XPUSHs(Perl_newSVpvf(aTHX_ "%"SVf"(%"SVf")",
 888                                                *namsvp, *argsvp));
 889                        else if (namok)
 890                             XPUSHs(Perl_newSVpvf(aTHX_ "%"SVf, *namsvp));
 891                        else
 892                             XPUSHs(&PL_sv_undef);
 893                        nitem++;
 894                        if (flgok) {
 895                             IV flags = SvIVX(*flgsvp);
 896
 897                             if (flags & PERLIO_F_UTF8) {
 898                                  XPUSHs(newSVpvn("utf8", 4));
 899                                  nitem++;
 900                             }
 901                        }
 902                   }
 903              }
 904
 905              SvREFCNT_dec(av);
 906
 907              XSRETURN(nitem);
 908         }
 909     }
 910 #endif
 911
 912     XSRETURN(0);
 913 }
 914
 915 XS(XS_Internals_hash_seed)
 916 {
 917     /* Using dXSARGS would also have dITEM and dSP,
 918      * which define 2 unused local variables.  */
 919     dAXMARK;
 920     (void)mark;
 921     XSRETURN_UV(PERL_HASH_SEED);
 922 }
 923
 924 XS(XS_Internals_rehash_seed)
 925 {
 926     /* Using dXSARGS would also have dITEM and dSP,
 927      * which define 2 unused local variables.  */
 928     dAXMARK;
 929     (void)mark;
 930     XSRETURN_UV(PL_rehash_seed);
 931 }
 932
 933 XS(XS_Internals_HvREHASH)       /* Subject to change  */
 934 {
 935     dXSARGS;
 936     if (SvROK(ST(0))) {
 937         const HV *hv = (HV *) SvRV(ST(0));
 938         if (items == 1 && SvTYPE(hv) == SVt_PVHV) {
 939             if (HvREHASH(hv))
 940                 XSRETURN_YES;
 941             else
 942                 XSRETURN_NO;
 943         }
 944     }
 945     Perl_croak(aTHX_ "Internals::HvREHASH $hashref");
 946 }
 947
 948 /*
 949  * Local variables:
 950  * c-indentation-style: bsd
 951  * c-basic-offset: 4
 952  * indent-tabs-mode: t
 953  * End:
 954  *
 955  * ex: set ts=8 sts=4 sw=4 noet:
 956  */