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Unused variable.
[perl5.git] / universal.c
index 6c555a1..da41eb9 100644 (file)
@@ -1,14 +1,35 @@
+/*    universal.c
+ *
+ *    Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
+ *    by Larry Wall and others
+ *
+ *    You may distribute under the terms of either the GNU General Public
+ *    License or the Artistic License, as specified in the README file.
+ *
+ */
+
+/*
+ * "The roots of those mountains must be roots indeed; there must be
+ * great secrets buried there which have not been discovered since the
+ * beginning." --Gandalf, relating Gollum's story
+ */
+
 #include "EXTERN.h"
 #define PERL_IN_UNIVERSAL_C
 #include "perl.h"
 
+#ifdef USE_PERLIO
+#include "perliol.h" /* For the PERLIO_F_XXX */
+#endif
+
 /*
  * Contributed by Graham Barr  <Graham.Barr@tiuk.ti.com>
  * The main guts of traverse_isa was actually copied from gv_fetchmeth
  */
 
 STATIC SV *
-S_isa_lookup(pTHX_ HV *stash, const char *name, int len, int level)
+S_isa_lookup(pTHX_ HV *stash, const char *name, HV* name_stash,
+             int len, int level)
 {
     AV* av;
     GV* gv;
@@ -16,8 +37,10 @@ S_isa_lookup(pTHX_ HV *stash, const char *name, int len, int level)
     HV* hv = Nullhv;
     SV* subgen = Nullsv;
 
-    if (!stash)
-       return &PL_sv_undef;
+    /* A stash/class can go by many names (ie. User == main::User), so 
+       we compare the stash itself just in case */
+    if (name_stash && (stash == name_stash))
+        return &PL_sv_yes;
 
     if (strEQ(HvNAME(stash), name))
        return &PL_sv_yes;
@@ -31,7 +54,7 @@ S_isa_lookup(pTHX_ HV *stash, const char *name, int len, int level)
     if (gvp && (gv = *gvp) != (GV*)&PL_sv_undef && (subgen = GvSV(gv))
        && (hv = GvHV(gv)))
     {
-       if (SvIV(subgen) == PL_sub_generation) {
+       if (SvIV(subgen) == (IV)PL_sub_generation) {
            SV* sv;
            SV** svp = (SV**)hv_fetch(hv, name, len, FALSE);
            if (svp && (sv = *svp) != (SV*)&PL_sv_undef) {
@@ -74,14 +97,14 @@ S_isa_lookup(pTHX_ HV *stash, const char *name, int len, int level)
                SV* sv = *svp++;
                HV* basestash = gv_stashsv(sv, FALSE);
                if (!basestash) {
-                   dTHR;
                    if (ckWARN(WARN_MISC))
-                       Perl_warner(aTHX_ WARN_SYNTAX,
-                            "Can't locate package %s for @%s::ISA",
-                           SvPVX(sv), HvNAME(stash));
+                       Perl_warner(aTHX_ packWARN(WARN_SYNTAX),
+                            "Can't locate package %"SVf" for @%s::ISA",
+                           sv, HvNAME(stash));
                    continue;
                }
-               if (&PL_sv_yes == isa_lookup(basestash, name, len, level + 1)) {
+               if (&PL_sv_yes == isa_lookup(basestash, name, name_stash, 
+                                             len, level + 1)) {
                    (void)hv_store(hv,name,len,&PL_sv_yes,0);
                    return &PL_sv_yes;
                }
@@ -94,6 +117,8 @@ S_isa_lookup(pTHX_ HV *stash, const char *name, int len, int level)
 }
 
 /*
+=head1 SV Manipulation Functions
+
 =for apidoc sv_derived_from
 
 Returns a boolean indicating whether the SV is derived from the specified
@@ -108,6 +133,7 @@ Perl_sv_derived_from(pTHX_ SV *sv, const char *name)
 {
     char *type;
     HV *stash;
+    HV *name_stash;
 
     stash = Nullhv;
     type = Nullch;
@@ -125,15 +151,39 @@ Perl_sv_derived_from(pTHX_ SV *sv, const char *name)
         stash = gv_stashsv(sv, FALSE);
     }
 
+    name_stash = gv_stashpv(name, FALSE);
+
     return (type && strEQ(type,name)) ||
-            (stash && isa_lookup(stash, name, strlen(name), 0) == &PL_sv_yes)
+            (stash && isa_lookup(stash, name, name_stash, strlen(name), 0) 
+             == &PL_sv_yes)
         ? TRUE
         : FALSE ;
 }
 
-void XS_UNIVERSAL_isa(pTHXo_ CV *cv);
-void XS_UNIVERSAL_can(pTHXo_ CV *cv);
-void XS_UNIVERSAL_VERSION(pTHXo_ CV *cv);
+#include "XSUB.h"
+
+void XS_UNIVERSAL_isa(pTHX_ CV *cv);
+void XS_UNIVERSAL_can(pTHX_ CV *cv);
+void XS_UNIVERSAL_VERSION(pTHX_ CV *cv);
+XS(XS_version_new);
+XS(XS_version_stringify);
+XS(XS_version_numify);
+XS(XS_version_vcmp);
+XS(XS_version_boolean);
+XS(XS_version_noop);
+XS(XS_utf8_is_utf8);
+XS(XS_utf8_valid);
+XS(XS_utf8_encode);
+XS(XS_utf8_decode);
+XS(XS_utf8_upgrade);
+XS(XS_utf8_downgrade);
+XS(XS_utf8_unicode_to_native);
+XS(XS_utf8_native_to_unicode);
+XS(XS_Internals_SvREADONLY);
+XS(XS_Internals_SvREFCNT);
+XS(XS_Internals_hv_clear_placehold);
+XS(XS_PerlIO_get_layers);
+XS(XS_Regexp_DESTROY);
 
 void
 Perl_boot_core_UNIVERSAL(pTHX)
@@ -143,9 +193,41 @@ Perl_boot_core_UNIVERSAL(pTHX)
     newXS("UNIVERSAL::isa",             XS_UNIVERSAL_isa,         file);
     newXS("UNIVERSAL::can",             XS_UNIVERSAL_can,         file);
     newXS("UNIVERSAL::VERSION",        XS_UNIVERSAL_VERSION,     file);
+    {
+       /* register the overloading (type 'A') magic */
+       PL_amagic_generation++;
+       /* Make it findable via fetchmethod */
+       newXS("version::()", XS_version_noop, file);
+       newXS("version::new", XS_version_new, file);
+       newXS("version::(\"\"", XS_version_stringify, file);
+       newXS("version::stringify", XS_version_stringify, file);
+       newXS("version::(0+", XS_version_numify, file);
+       newXS("version::numify", XS_version_numify, file);
+       newXS("version::(cmp", XS_version_vcmp, file);
+       newXS("version::(<=>", XS_version_vcmp, file);
+       newXS("version::vcmp", XS_version_vcmp, file);
+       newXS("version::(bool", XS_version_boolean, file);
+       newXS("version::boolean", XS_version_boolean, file);
+       newXS("version::(nomethod", XS_version_noop, file);
+       newXS("version::noop", XS_version_noop, file);
+    }
+    newXS("utf8::is_utf8", XS_utf8_is_utf8, file);
+    newXS("utf8::valid", XS_utf8_valid, file);
+    newXS("utf8::encode", XS_utf8_encode, file);
+    newXS("utf8::decode", XS_utf8_decode, file);
+    newXS("utf8::upgrade", XS_utf8_upgrade, file);
+    newXS("utf8::downgrade", XS_utf8_downgrade, file);
+    newXS("utf8::native_to_unicode", XS_utf8_native_to_unicode, file);
+    newXS("utf8::unicode_to_native", XS_utf8_unicode_to_native, file);
+    newXSproto("Internals::SvREADONLY",XS_Internals_SvREADONLY, file, "\\[$%@];$");
+    newXSproto("Internals::SvREFCNT",XS_Internals_SvREFCNT, file, "\\[$%@];$");
+    newXSproto("Internals::hv_clear_placeholders",
+               XS_Internals_hv_clear_placehold, file, "\\%");
+    newXSproto("PerlIO::get_layers",
+               XS_PerlIO_get_layers, file, "*;@");
+    newXS("Regexp::DESTROY", XS_Regexp_DESTROY, file);
 }
 
-#include "XSUB.h"
 
 XS(XS_UNIVERSAL_isa)
 {
@@ -162,7 +244,8 @@ XS(XS_UNIVERSAL_isa)
     if (SvGMAGICAL(sv))
        mg_get(sv);
 
-    if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))))
+    if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))
+               || (SvGMAGICAL(sv) && SvPOKp(sv) && SvCUR(sv))))
        XSRETURN_UNDEF;
 
     name = (char *)SvPV(ST(1),n_a);
@@ -188,7 +271,8 @@ XS(XS_UNIVERSAL_can)
     if (SvGMAGICAL(sv))
        mg_get(sv);
 
-    if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))))
+    if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))
+               || (SvGMAGICAL(sv) && SvPOKp(sv) && SvCUR(sv))))
        XSRETURN_UNDEF;
 
     name = (char *)SvPV(ST(1),n_a);
@@ -249,54 +333,544 @@ XS(XS_UNIVERSAL_VERSION)
        STRLEN len;
        SV *req = ST(1);
 
-       if (undef)
-           Perl_croak(aTHX_ "%s does not define $%s::VERSION--version check failed",
-                      HvNAME(pkg), HvNAME(pkg));
-
-       if (!SvNIOK(sv) && SvPOK(sv)) {
-           char *str = SvPVx(sv,len);
-           while (len) {
-               --len;
-               /* XXX could DWIM "1.2.3" here */
-               if (!isDIGIT(str[len]) && str[len] != '.' && str[len] != '_')
-                   break;
-           }
-           if (len) {
-               if (SvNOK(req) && SvPOK(req)) {
-                   /* they said C<use Foo v1.2.3> and $Foo::VERSION
-                    * doesn't look like a float: do string compare */
-                   if (sv_cmp(req,sv) == 1) {
-                       Perl_croak(aTHX_ "%s v%vd required--"
-                                  "this is only v%vd",
-                                  HvNAME(pkg), req, sv);
-                   }
-                   goto finish;
-               }
-               /* they said C<use Foo 1.002_003> and $Foo::VERSION
-                * doesn't look like a float: force numeric compare */
-               (void)SvUPGRADE(sv, SVt_PVNV);
-               SvNVX(sv) = str_to_version(sv);
-               SvPOK_off(sv);
-               SvNOK_on(sv);
-           }
-       }
-       /* if we get here, we're looking for a numeric comparison,
-        * so force the required version into a float, even if they
-        * said C<use Foo v1.2.3> */
-       if (SvNOK(req) && SvPOK(req)) {
-           NV n = SvNV(req);
-           req = sv_newmortal();
-           sv_setnv(req, n);
+       if (undef) {
+            if (pkg)
+                 Perl_croak(aTHX_
+                            "%s does not define $%s::VERSION--version check failed",
+                            HvNAME(pkg), HvNAME(pkg));
+            else {
+                 char *str = SvPVx(ST(0), len);
+
+                 Perl_croak(aTHX_
+                            "%s defines neither package nor VERSION--version check failed", str);
+            }
        }
+       if ( !sv_derived_from(sv, "version"))
+           sv = new_version(sv);
+
+       if ( !sv_derived_from(req, "version"))
+           req = new_version(req);
 
-       if (SvNV(req) > SvNV(sv))
-           Perl_croak(aTHX_ "%s version %s required--this is only version %s",
-                 HvNAME(pkg), SvPV(req,len), SvPV(sv,len));
+       if ( vcmp( SvRV(req), SvRV(sv) ) > 0 )
+           Perl_croak(aTHX_
+               "%s version %"SVf" required--this is only version %"SVf,
+               HvNAME(pkg), req, sv);
     }
 
-finish:
     ST(0) = sv;
 
     XSRETURN(1);
 }
 
+XS(XS_version_new)
+{
+    dXSARGS;
+    if (items > 3)
+       Perl_croak(aTHX_ "Usage: version::new(class, version)");
+    SP -= items;
+    {
+/*     char *  class = (char *)SvPV_nolen(ST(0)); */
+        SV *version = ST(1);
+       if (items == 3 )
+       {
+           char *vs = savepvn(SvPVX(ST(2)),SvCUR(ST(2)));
+           version = Perl_newSVpvf(aTHX_ "v%s",vs);
+       }
+
+       PUSHs(new_version(version));
+       PUTBACK;
+       return;
+    }
+}
+
+XS(XS_version_stringify)
+{
+    dXSARGS;
+    if (items < 1)
+       Perl_croak(aTHX_ "Usage: version::stringify(lobj, ...)");
+    SP -= items;
+    {
+       SV *    lobj;
+
+        if (sv_derived_from(ST(0), "version")) {
+                SV *tmp = SvRV(ST(0));
+               lobj = tmp;
+        }
+        else
+                Perl_croak(aTHX_ "lobj is not of type version");
+
+{
+    PUSHs(vstringify(lobj));
+}
+
+       PUTBACK;
+       return;
+    }
+}
+
+XS(XS_version_numify)
+{
+    dXSARGS;
+    if (items < 1)
+       Perl_croak(aTHX_ "Usage: version::numify(lobj, ...)");
+    SP -= items;
+    {
+       SV *    lobj;
+
+        if (sv_derived_from(ST(0), "version")) {
+                SV *tmp = SvRV(ST(0));
+               lobj = tmp;
+        }
+        else
+                Perl_croak(aTHX_ "lobj is not of type version");
+
+{
+    PUSHs(vnumify(lobj));
+}
+
+       PUTBACK;
+       return;
+    }
+}
+
+XS(XS_version_vcmp)
+{
+    dXSARGS;
+    if (items < 1)
+       Perl_croak(aTHX_ "Usage: version::vcmp(lobj, ...)");
+    SP -= items;
+    {
+       SV *    lobj;
+
+        if (sv_derived_from(ST(0), "version")) {
+                SV *tmp = SvRV(ST(0));
+               lobj = tmp;
+        }
+        else
+                Perl_croak(aTHX_ "lobj is not of type version");
+
+{
+    SV *rs;
+    SV *rvs;
+    SV * robj = ST(1);
+    IV  swap = (IV)SvIV(ST(2));
+
+    if ( ! sv_derived_from(robj, "version") )
+    {
+       robj = new_version(robj);
+    }
+    rvs = SvRV(robj);
+
+    if ( swap )
+    {
+        rs = newSViv(vcmp(rvs,lobj));
+    }
+    else
+    {
+        rs = newSViv(vcmp(lobj,rvs));
+    }
+
+    PUSHs(rs);
+}
+
+       PUTBACK;
+       return;
+    }
+}
+
+XS(XS_version_boolean)
+{
+    dXSARGS;
+    if (items < 1)
+       Perl_croak(aTHX_ "Usage: version::boolean(lobj, ...)");
+    SP -= items;
+    {
+       SV *    lobj;
+
+        if (sv_derived_from(ST(0), "version")) {
+                SV *tmp = SvRV(ST(0));
+               lobj = tmp;
+        }
+        else
+                Perl_croak(aTHX_ "lobj is not of type version");
+
+{
+    SV *rs;
+    rs = newSViv( vcmp(lobj,new_version(newSVpvn("0",1))) );
+    PUSHs(rs);
+}
+
+       PUTBACK;
+       return;
+    }
+}
+
+XS(XS_version_noop)
+{
+    dXSARGS;
+    if (items < 1)
+       Perl_croak(aTHX_ "Usage: version::noop(lobj, ...)");
+    {
+       SV *    lobj;
+
+        if (sv_derived_from(ST(0), "version")) {
+                SV *tmp = SvRV(ST(0));
+               lobj = tmp;
+        }
+        else
+                Perl_croak(aTHX_ "lobj is not of type version");
+
+{
+    Perl_croak(aTHX_ "operation not supported with version object");
+}
+
+    }
+    XSRETURN_EMPTY;
+}
+
+XS(XS_utf8_is_utf8)
+{
+    dXSARGS;
+    if (items != 1)
+       Perl_croak(aTHX_ "Usage: utf8::is_utf8(sv)");
+    {
+       SV *    sv = ST(0);
+ {
+  if (SvUTF8(sv))
+   XSRETURN_YES;
+  else
+   XSRETURN_NO;
+ }
+    }
+    XSRETURN_EMPTY;
+}
+
+XS(XS_utf8_valid)
+{
+    dXSARGS;
+    if (items != 1)
+       Perl_croak(aTHX_ "Usage: utf8::valid(sv)");
+    {
+       SV *    sv = ST(0);
+ {
+  STRLEN len;
+  char *s = SvPV(sv,len);
+  if (!SvUTF8(sv) || is_utf8_string((U8*)s,len))
+   XSRETURN_YES;
+  else
+   XSRETURN_NO;
+ }
+    }
+    XSRETURN_EMPTY;
+}
+
+XS(XS_utf8_encode)
+{
+    dXSARGS;
+    if (items != 1)
+       Perl_croak(aTHX_ "Usage: utf8::encode(sv)");
+    {
+       SV *    sv = ST(0);
+
+       sv_utf8_encode(sv);
+    }
+    XSRETURN_EMPTY;
+}
+
+XS(XS_utf8_decode)
+{
+    dXSARGS;
+    if (items != 1)
+       Perl_croak(aTHX_ "Usage: utf8::decode(sv)");
+    {
+       SV *    sv = ST(0);
+       bool    RETVAL;
+
+       RETVAL = sv_utf8_decode(sv);
+       ST(0) = boolSV(RETVAL);
+       sv_2mortal(ST(0));
+    }
+    XSRETURN(1);
+}
+
+XS(XS_utf8_upgrade)
+{
+    dXSARGS;
+    if (items != 1)
+       Perl_croak(aTHX_ "Usage: utf8::upgrade(sv)");
+    {
+       SV *    sv = ST(0);
+       STRLEN  RETVAL;
+       dXSTARG;
+
+       RETVAL = sv_utf8_upgrade(sv);
+       XSprePUSH; PUSHi((IV)RETVAL);
+    }
+    XSRETURN(1);
+}
+
+XS(XS_utf8_downgrade)
+{
+    dXSARGS;
+    if (items < 1 || items > 2)
+       Perl_croak(aTHX_ "Usage: utf8::downgrade(sv, failok=0)");
+    {
+       SV *    sv = ST(0);
+       bool    failok;
+       bool    RETVAL;
+
+       if (items < 2)
+           failok = 0;
+       else {
+           failok = (int)SvIV(ST(1));
+       }
+
+       RETVAL = sv_utf8_downgrade(sv, failok);
+       ST(0) = boolSV(RETVAL);
+       sv_2mortal(ST(0));
+    }
+    XSRETURN(1);
+}
+
+XS(XS_utf8_native_to_unicode)
+{
+ dXSARGS;
+ UV uv = SvUV(ST(0));
+
+ if (items > 1)
+     Perl_croak(aTHX_ "Usage: utf8::native_to_unicode(sv)");
+
+ ST(0) = sv_2mortal(newSViv(NATIVE_TO_UNI(uv)));
+ XSRETURN(1);
+}
+
+XS(XS_utf8_unicode_to_native)
+{
+ dXSARGS;
+ UV uv = SvUV(ST(0));
+
+ if (items > 1)
+     Perl_croak(aTHX_ "Usage: utf8::unicode_to_native(sv)");
+
+ ST(0) = sv_2mortal(newSViv(UNI_TO_NATIVE(uv)));
+ XSRETURN(1);
+}
+
+XS(XS_Internals_SvREADONLY)    /* This is dangerous stuff. */
+{
+    dXSARGS;
+    SV *sv = SvRV(ST(0));
+    if (items == 1) {
+        if (SvREADONLY(sv))
+            XSRETURN_YES;
+        else
+            XSRETURN_NO;
+    }
+    else if (items == 2) {
+       if (SvTRUE(ST(1))) {
+           SvREADONLY_on(sv);
+           XSRETURN_YES;
+       }
+       else {
+           /* I hope you really know what you are doing. */
+           SvREADONLY_off(sv);
+           XSRETURN_NO;
+       }
+    }
+    XSRETURN_UNDEF; /* Can't happen. */
+}
+
+XS(XS_Internals_SvREFCNT)      /* This is dangerous stuff. */
+{
+    dXSARGS;
+    SV *sv = SvRV(ST(0));
+    if (items == 1)
+        XSRETURN_IV(SvREFCNT(sv) - 1); /* Minus the ref created for us. */
+    else if (items == 2) {
+         /* I hope you really know what you are doing. */
+        SvREFCNT(sv) = SvIV(ST(1));
+        XSRETURN_IV(SvREFCNT(sv));
+    }
+    XSRETURN_UNDEF; /* Can't happen. */
+}
+
+/* Maybe this should return the number of placeholders found in scalar context,
+   and a list of them in list context.  */
+XS(XS_Internals_hv_clear_placehold)
+{
+    dXSARGS;
+    HV *hv = (HV *) SvRV(ST(0));
+
+    /* I don't care how many parameters were passed in, but I want to avoid
+       the unused variable warning. */
+
+    items = (I32)HvPLACEHOLDERS(hv);
+
+    if (items) {
+        HE *entry;
+        I32 riter = HvRITER(hv);
+        HE *eiter = HvEITER(hv);
+        hv_iterinit(hv);
+        /* This may look suboptimal with the items *after* the iternext, but
+           it's quite deliberate. We only get here with items==0 if we've
+           just deleted the last placeholder in the hash. If we've just done
+           that then it means that the hash is in lazy delete mode, and the
+           HE is now only referenced in our iterator. If we just quit the loop
+           and discarded our iterator then the HE leaks. So we do the && the
+           other way to ensure iternext is called just one more time, which
+           has the side effect of triggering the lazy delete.  */
+        while ((entry = hv_iternext_flags(hv, HV_ITERNEXT_WANTPLACEHOLDERS))
+            && items) {
+            SV *val = hv_iterval(hv, entry);
+
+            if (val == &PL_sv_undef) {
+
+                /* It seems that I have to go back in the front of the hash
+                   API to delete a hash, even though I have a HE structure
+                   pointing to the very entry I want to delete, and could hold
+                   onto the previous HE that points to it. And it's easier to
+                   go in with SVs as I can then specify the precomputed hash,
+                   and don't have fun and games with utf8 keys.  */
+                SV *key = hv_iterkeysv(entry);
+
+                hv_delete_ent (hv, key, G_DISCARD, HeHASH(entry));
+                items--;
+            }
+        }
+        HvRITER(hv) = riter;
+        HvEITER(hv) = eiter;
+    }
+
+    XSRETURN(0);
+}
+
+XS(XS_Regexp_DESTROY)
+{
+
+}
+
+XS(XS_PerlIO_get_layers)
+{
+    dXSARGS;
+    if (items < 1 || items % 2 == 0)
+       Perl_croak(aTHX_ "Usage: PerlIO_get_layers(filehandle[,args])");
+#ifdef USE_PERLIO
+    {
+       SV *    sv;
+       GV *    gv;
+       IO *    io;
+       bool    input = TRUE;
+       bool    details = FALSE;
+
+       if (items > 1) {
+            SV **svp;
+            
+            for (svp = MARK + 2; svp <= SP; svp += 2) {
+                 SV **varp = svp;
+                 SV **valp = svp + 1;
+                 STRLEN klen;
+                 char *key = SvPV(*varp, klen);
+
+                 switch (*key) {
+                 case 'i':
+                      if (klen == 5 && memEQ(key, "input", 5)) {
+                           input = SvTRUE(*valp);
+                           break;
+                      }
+                      goto fail;
+                 case 'o': 
+                      if (klen == 6 && memEQ(key, "output", 6)) {
+                           input = !SvTRUE(*valp);
+                           break;
+                      }
+                      goto fail;
+                 case 'd':
+                      if (klen == 7 && memEQ(key, "details", 7)) {
+                           details = SvTRUE(*valp);
+                           break;
+                      }
+                      goto fail;
+                 default:
+                 fail:
+                      Perl_croak(aTHX_
+                                 "get_layers: unknown argument '%s'",
+                                 key);
+                 }
+            }
+
+            SP -= (items - 1);
+       }
+
+       sv = POPs;
+       gv = (GV*)sv;
+
+       if (!isGV(sv)) {
+            if (SvROK(sv) && isGV(SvRV(sv)))
+                 gv = (GV*)SvRV(sv);
+            else
+                 gv = gv_fetchpv(SvPVX(sv), FALSE, SVt_PVIO);
+       }
+
+       if (gv && (io = GvIO(gv))) {
+            dTARGET;
+            AV* av = PerlIO_get_layers(aTHX_ input ?
+                                       IoIFP(io) : IoOFP(io));
+            I32 i;
+            I32 last = av_len(av);
+            I32 nitem = 0;
+            
+            for (i = last; i >= 0; i -= 3) {
+                 SV **namsvp;
+                 SV **argsvp;
+                 SV **flgsvp;
+                 bool namok, argok, flgok;
+
+                 namsvp = av_fetch(av, i - 2, FALSE);
+                 argsvp = av_fetch(av, i - 1, FALSE);
+                 flgsvp = av_fetch(av, i,     FALSE);
+
+                 namok = namsvp && *namsvp && SvPOK(*namsvp);
+                 argok = argsvp && *argsvp && SvPOK(*argsvp);
+                 flgok = flgsvp && *flgsvp && SvIOK(*flgsvp);
+
+                 if (details) {
+                      XPUSHs(namok ?
+                            newSVpv(SvPVX(*namsvp), 0) : &PL_sv_undef);
+                      XPUSHs(argok ?
+                            newSVpv(SvPVX(*argsvp), 0) : &PL_sv_undef);
+                      if (flgok)
+                           XPUSHi(SvIVX(*flgsvp));
+                      else
+                           XPUSHs(&PL_sv_undef);
+                      nitem += 3;
+                 }
+                 else {
+                      if (namok && argok)
+                           XPUSHs(Perl_newSVpvf(aTHX_ "%"SVf"(%"SVf")",
+                                              *namsvp, *argsvp));
+                      else if (namok)
+                           XPUSHs(Perl_newSVpvf(aTHX_ "%"SVf, *namsvp));
+                      else
+                           XPUSHs(&PL_sv_undef);
+                      nitem++;
+                      if (flgok) {
+                           IV flags = SvIVX(*flgsvp);
+
+                           if (flags & PERLIO_F_UTF8) {
+                                XPUSHs(newSVpvn("utf8", 4));
+                                nitem++;
+                           }
+                      }
+                 }
+            }
+
+            SvREFCNT_dec(av);
+
+            XSRETURN(nitem);
+       }
+    }
+#endif
+
+    XSRETURN(0);
+}
+