X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=universal.c;h=486b366f4aec947005874bf10144a2860b605e53;hb=b4bc5691c8dfad19b52d103e3b12af9342fcea38;hp=b082da67ffe0234b5534819843f612e26482cb11;hpb=dc848c6f6758d4d951bb5c7a9f432e6390e094df;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/universal.c b/universal.c
index b082da6..486b366 100644
--- a/universal.c
+++ b/universal.c
@@ -1,46 +1,75 @@
+/*    universal.c
+ *
+ *    Copyright (c) 1997-2002, Larry Wall
+ *
+ *    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"
-#include "XSUB.h"
 
 /*
  * Contributed by Graham Barr  <Graham.Barr@tiuk.ti.com>
  * The main guts of traverse_isa was actually copied from gv_fetchmeth
  */
 
-static SV *
-isa_lookup(stash, name, len, level)
-HV *stash;
-char *name;
-int len;
-int level;
+STATIC SV *
+S_isa_lookup(pTHX_ HV *stash, const char *name, HV* name_stash,
+             int len, int level)
 {
     AV* av;
     GV* gv;
     GV** gvp;
     HV* hv = Nullhv;
+    SV* subgen = Nullsv;
 
-    if (!stash)
-	return &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 &sv_yes;
+    if (strEQ(HvNAME(stash), name))
+	return &PL_sv_yes;
 
     if (level > 100)
-	croak("Recursive inheritance detected");
+	Perl_croak(aTHX_ "Recursive inheritance detected in package '%s'",
+		   HvNAME(stash));
 
     gvp = (GV**)hv_fetch(stash, "::ISA::CACHE::", 14, FALSE);
 
-    if (gvp && (gv = *gvp) != (GV*)&sv_undef && (hv = GvHV(gv))) {
-	SV* sv;
-	SV** svp = (SV**)hv_fetch(hv, name, len, FALSE);
-	if (svp && (sv = *svp) != (SV*)&sv_undef)
-	    return sv;
+    if (gvp && (gv = *gvp) != (GV*)&PL_sv_undef && (subgen = GvSV(gv))
+	&& (hv = GvHV(gv)))
+    {
+	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) {
+	        DEBUG_o( Perl_deb(aTHX_ "Using cached ISA %s for package %s\n",
+				  name, HvNAME(stash)) );
+		return sv;
+	    }
+	}
+	else {
+	    DEBUG_o( Perl_deb(aTHX_ "ISA Cache in package %s is stale\n",
+			      HvNAME(stash)) );
+	    hv_clear(hv);
+	    sv_setiv(subgen, PL_sub_generation);
+	}
     }
 
     gvp = (GV**)hv_fetch(stash,"ISA",3,FALSE);
-    
-    if (gvp && (gv = *gvp) != (GV*)&sv_undef && (av = GvAV(gv))) {
-	if(!hv) {
+
+    if (gvp && (gv = *gvp) != (GV*)&PL_sv_undef && (av = GvAV(gv))) {
+	if (!hv || !subgen) {
 	    gvp = (GV**)hv_fetch(stash, "::ISA::CACHE::", 14, TRUE);
 
 	    gv = *gvp;
@@ -48,83 +77,173 @@ int level;
 	    if (SvTYPE(gv) != SVt_PVGV)
 		gv_init(gv, stash, "::ISA::CACHE::", 14, TRUE);
 
-	    hv = GvHVn(gv);
+	    if (!hv)
+		hv = GvHVn(gv);
+	    if (!subgen) {
+		subgen = newSViv(PL_sub_generation);
+		GvSV(gv) = subgen;
+	    }
 	}
-	if(hv) {
+	if (hv) {
 	    SV** svp = AvARRAY(av);
-	    I32 items = AvFILL(av) + 1;
+	    /* NOTE: No support for tied ISA */
+	    I32 items = AvFILLp(av) + 1;
 	    while (items--) {
 		SV* sv = *svp++;
 		HV* basestash = gv_stashsv(sv, FALSE);
 		if (!basestash) {
-		    if (dowarn)
-			warn("Can't locate package %s for @%s::ISA",
+		    if (ckWARN(WARN_MISC))
+			Perl_warner(aTHX_ packWARN(WARN_SYNTAX),
+		             "Can't locate package %s for @%s::ISA",
 			    SvPVX(sv), HvNAME(stash));
 		    continue;
 		}
-		if(&sv_yes == isa_lookup(basestash, name, len, level + 1)) {
-		    (void)hv_store(hv,name,len,&sv_yes,0);
-		    return &sv_yes;
+		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;
 		}
 	    }
-	    (void)hv_store(hv,name,len,&sv_no,0);
+	    (void)hv_store(hv,name,len,&PL_sv_no,0);
 	}
     }
 
-    return &sv_no;
+    return boolSV(strEQ(name, "UNIVERSAL"));
 }
 
+/*
+=head1 SV Manipulation Functions
+
+=for apidoc sv_derived_from
+
+Returns a boolean indicating whether the SV is derived from the specified
+class.  This is the function that implements C<UNIVERSAL::isa>.  It works
+for class names as well as for objects.
+
+=cut
+*/
+
 bool
-sv_derived_from(sv, name)
-SV * sv ;
-char * name ;
+Perl_sv_derived_from(pTHX_ SV *sv, const char *name)
 {
-    SV *rv;
     char *type;
     HV *stash;
-  
+    HV *name_stash;
+
     stash = Nullhv;
     type = Nullch;
- 
+
     if (SvGMAGICAL(sv))
         mg_get(sv) ;
 
     if (SvROK(sv)) {
         sv = SvRV(sv);
         type = sv_reftype(sv,0);
-        if(SvOBJECT(sv))
+        if (SvOBJECT(sv))
             stash = SvSTASH(sv);
     }
     else {
         stash = gv_stashsv(sv, FALSE);
     }
- 
+
+    name_stash = gv_stashpv(name, FALSE);
+
     return (type && strEQ(type,name)) ||
-            (stash && isa_lookup(stash, name, strlen(name), 0) == &sv_yes)
+            (stash && isa_lookup(stash, name, name_stash, strlen(name), 0) 
+             == &PL_sv_yes)
         ? TRUE
         : FALSE ;
- 
+}
+
+#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_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);
+
+void
+Perl_boot_core_UNIVERSAL(pTHX)
+{
+    char *file = __FILE__;
+
+    newXS("UNIVERSAL::isa",             XS_UNIVERSAL_isa,         file);
+    newXS("UNIVERSAL::can",             XS_UNIVERSAL_can,         file);
+    newXS("UNIVERSAL::VERSION", 	XS_UNIVERSAL_VERSION, 	  file);
+    {
+	/* create the package stash for version objects */
+	HV *hv = get_hv("version::OVERLOAD",TRUE);
+	SV *sv = *hv_fetch(hv,"register",8,1);
+	sv_inc(sv);
+	SvSETMAGIC(sv);
+	/* Make it findable via fetchmethod */
+	newXS("version::()", NULL, 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::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, "\\%");
 }
 
 
-static
 XS(XS_UNIVERSAL_isa)
 {
     dXSARGS;
     SV *sv;
     char *name;
+    STRLEN n_a;
 
     if (items != 2)
-	croak("Usage: UNIVERSAL::isa(reference, kind)");
+	Perl_croak(aTHX_ "Usage: UNIVERSAL::isa(reference, kind)");
 
     sv = ST(0);
-    name = (char *)SvPV(ST(1),na);
+
+    if (SvGMAGICAL(sv))
+	mg_get(sv);
+
+    if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))))
+	XSRETURN_UNDEF;
+
+    name = (char *)SvPV(ST(1),n_a);
 
     ST(0) = boolSV(sv_derived_from(sv, name));
     XSRETURN(1);
 }
 
-static
 XS(XS_UNIVERSAL_can)
 {
     dXSARGS;
@@ -132,17 +251,25 @@ XS(XS_UNIVERSAL_can)
     char *name;
     SV   *rv;
     HV   *pkg = NULL;
+    STRLEN n_a;
 
     if (items != 2)
-	croak("Usage: UNIVERSAL::can(object-ref, method)");
+	Perl_croak(aTHX_ "Usage: UNIVERSAL::can(object-ref, method)");
 
     sv = ST(0);
-    name = (char *)SvPV(ST(1),na);
-    rv = &sv_undef;
 
-    if(SvROK(sv)) {
+    if (SvGMAGICAL(sv))
+	mg_get(sv);
+
+    if (!SvOK(sv) || !(SvROK(sv) || (SvPOK(sv) && SvCUR(sv))))
+	XSRETURN_UNDEF;
+
+    name = (char *)SvPV(ST(1),n_a);
+    rv = &PL_sv_undef;
+
+    if (SvROK(sv)) {
         sv = (SV*)SvRV(sv);
-        if(SvOBJECT(sv))
+        if (SvOBJECT(sv))
             pkg = SvSTASH(sv);
     }
     else {
@@ -159,7 +286,6 @@ XS(XS_UNIVERSAL_can)
     XSRETURN(1);
 }
 
-static
 XS(XS_UNIVERSAL_VERSION)
 {
     dXSARGS;
@@ -168,12 +294,11 @@ XS(XS_UNIVERSAL_VERSION)
     GV *gv;
     SV *sv;
     char *undef;
-    double req;
 
-    if(SvROK(ST(0))) {
+    if (SvROK(ST(0))) {
         sv = (SV*)SvRV(ST(0));
-        if(!SvOBJECT(sv))
-            croak("Cannot find version of an unblessed reference");
+        if (!SvOBJECT(sv))
+            Perl_croak(aTHX_ "Cannot find version of an unblessed reference");
         pkg = SvSTASH(sv);
     }
     else {
@@ -182,32 +307,446 @@ XS(XS_UNIVERSAL_VERSION)
 
     gvp = pkg ? (GV**)hv_fetch(pkg,"VERSION",7,FALSE) : Null(GV**);
 
-    if (gvp && (gv = *gvp) != (GV*)&sv_undef && (sv = GvSV(gv))) {
+    if (gvp && isGV(gv = *gvp) && SvOK(sv = GvSV(gv))) {
         SV *nsv = sv_newmortal();
         sv_setsv(nsv, sv);
         sv = nsv;
         undef = Nullch;
     }
     else {
-        sv = (SV*)&sv_undef;
+        sv = (SV*)&PL_sv_undef;
         undef = "(undef)";
     }
 
-    if (items > 1 && (undef || (req = SvNV(ST(1)), req > SvNV(sv))))
-	croak("%s version %s required--this is only version %s",
-	      HvNAME(pkg), SvPV(ST(1),na), undef ? undef : SvPV(sv,na));
+    if (items > 1) {
+	STRLEN len;
+	SV *req = ST(1);
+
+	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 (!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%"VDf" required--"
+				   "this is only v%"VDf,
+				   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 (SvNV(req) > SvNV(sv))
+	    Perl_croak(aTHX_ "%s version %s required--this is only version %s",
+		       HvNAME(pkg), SvPV_nolen(req), SvPV_nolen(sv));
+    }
 
+finish:
     ST(0) = sv;
 
     XSRETURN(1);
 }
 
-void
-boot_core_UNIVERSAL()
+XS(XS_version_new)
 {
-    char *file = __FILE__;
+    dXSARGS;
+    if (items != 2)
+	Perl_croak(aTHX_ "Usage: version::new(class, version)");
+    SP -= items;
+    {
+/*	char *	class = (char *)SvPV_nolen(ST(0)); */
+	SV *	version = ST(1);
 
-    newXS("UNIVERSAL::isa",             XS_UNIVERSAL_isa,         file);
-    newXS("UNIVERSAL::can",             XS_UNIVERSAL_can,         file);
-    newXS("UNIVERSAL::VERSION", 	XS_UNIVERSAL_VERSION, 	  file);
+{
+    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
+                croak("lobj is not of type version");
+
+{
+    SV  *vs = NEWSV(92,5);
+    if ( lobj == SvRV(PL_patchlevel) )
+	sv_catsv(vs,lobj);
+    else
+	vstringify(vs,lobj);
+    PUSHs(vs);
+}
+
+	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
+                croak("lobj is not of type version");
+
+{
+    SV  *vs = NEWSV(92,5);
+    vnumify(vs,lobj);
+    PUSHs(vs);
+}
+
+	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
+                croak("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(sv_cmp(rvs,lobj));
+    }
+    else
+    {
+        rs = newSViv(sv_cmp(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
+                croak("lobj is not of type version");
+
+{
+    SV	*rs;
+    rs = newSViv(sv_cmp(lobj,Nullsv));
+    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
+                croak("lobj is not of type version");
+
+{
+    croak("operation not supported with version object");
+}
+
+    }
+    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);
 }