Integrate:

[ 21604]
Add Internals::HvREHASH to expose the rehashing flag
t/op/hash.t tests that pathological data triggers rehashing
p4raw-link: @21604 on //depot/perl: 05619474c45b1f1e16eb70c1d9f8b991a7ad459a

p4raw-id: //depot/maint-5.8/perl@21605
p4raw-branched: from //depot/perl@21603 'branch in' t/op/hash.t
p4raw-integrated: from //depot/perl@21603 'merge in' universal.c
	(@21441..)

2 files changed, 43 insertions, 0 deletions

diff --git a/t/op/hash.t b/t/op/hash.t
new file mode 100644
index 0000000000..3beae8432a
--- /dev/null
+++ b/t/op/hash.t
@@ -0,0 +1,27 @@
+#!./perl -w
+
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require './test.pl';
+}
+
+use strict;
+
+plan tests => 3;
+
+my %h;
+
+ok (!Internals::HvREHASH(%h), "hash doesn't start with rehash flag on");
+
+foreach (1..10) {
+  $h{"\0"x$_}++;
+}
+
+ok (!Internals::HvREHASH(%h), "10 entries doesn't trigger rehash");
+
+foreach (11..20) {
+  $h{"\0"x$_}++;
+}
+
+ok (Internals::HvREHASH(%h), "20 entries triggers rehash");
diff --git a/universal.c b/universal.c
index ab3fd1ccf9..96f4906206 100644
--- a/universal.c
+++ b/universal.c
@@ -181,6 +181,7 @@ XS(XS_Internals_hv_clear_placehold);
 XS(XS_PerlIO_get_layers);
 XS(XS_Regexp_DESTROY);
 XS(XS_Internals_hash_seed);
+XS(XS_Internals_HvREHASH);
 
 void
 Perl_boot_core_UNIVERSAL(pTHX)
@@ -206,6 +207,7 @@ Perl_boot_core_UNIVERSAL(pTHX)
                XS_PerlIO_get_layers, file, "*;@");
     newXS("Regexp::DESTROY", XS_Regexp_DESTROY, file);
     newXSproto("Internals::hash_seed",XS_Internals_hash_seed, file, "");
+    newXSproto("Internals::HvREHASH", XS_Internals_HvREHASH, file, "\\%");
 }
 
 
@@ -726,3 +728,17 @@ XS(XS_Internals_hash_seed)
     XSRETURN_UV(PERL_HASH_SEED);
 }
 
+XS(XS_Internals_HvREHASH)	/* Subject to change  */
+{
+    dXSARGS;
+    if (SvROK(ST(0))) {
+	HV *hv = (HV *) SvRV(ST(0));
+	if (items == 1 && SvTYPE(hv) == SVt_PVHV) {
+	    if (HvREHASH(hv))
+		XSRETURN_YES;
+	    else
+		XSRETURN_NO;
+	}
+    }
+    Perl_croak(aTHX_ "Internals::HvREHASH $hashref");
+}