X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=XS.xs;h=07f0a9ba05063863b82a6e9dfdee868c1ada9666;hb=d581cf05b55a8bd9fe6268a1051ffdd82bc8f403;hp=1ad66143340ea15f7e9c8dc1813339fb2a8acb53;hpb=68fe9f2928a5a423e6d31eaf4b2bf0c17c9bfb27;p=gitmo%2FClass-C3-XS.git

diff --git a/XS.xs b/XS.xs
index 1ad6614..07f0a9b 100644
--- a/XS.xs
+++ b/XS.xs
@@ -99,7 +99,7 @@ __mro_linear_isa_c3(pTHX_ HV* stash, HV* cache, I32 level)
     if(isa && AvFILLp(isa) >= 0) {
         SV** seqs_ptr;
         I32 seqs_items;
-        HV* const tails = (HV*)sv_2mortal((SV*)newHV());
+        HV* tails;
         AV* const seqs = (AV*)sv_2mortal((SV*)newAV());
         I32* heads;
 
@@ -122,10 +122,48 @@ __mro_linear_isa_c3(pTHX_ HV* stash, HV* cache, I32 level)
             else {
                 /* recursion */
                 AV* const isa_lin = __mro_linear_isa_c3(aTHX_ isa_item_stash, cache, level + 1);
+
+                if(items == 0 && AvFILLp(seqs) == -1) {
+                    /* Only one parent class. For this case, the C3
+                       linearisation is this class followed by the parent's
+                       linearisation, so don't bother with the expensive
+                       calculation.  */
+                    SV **svp;
+                    I32 subrv_items = AvFILLp(isa_lin) + 1;
+                    SV *const *subrv_p = AvARRAY(isa_lin);
+
+                    /* Hijack the allocated but unused array seqs to be the
+                       return value. It's currently mortalised.  */
+
+                    retval = seqs;
+
+                    av_extend(retval, subrv_items);
+                    AvFILLp(retval) = subrv_items;
+                    svp = AvARRAY(retval);
+
+                    /* First entry is this class.  */
+                    *svp++ = newSVpvn(stashname, stashname_len);
+
+                    while(subrv_items--) {
+                        /* These values are unlikely to be shared hash key
+                           scalars, so no point in adding code to optimising
+                           for a case that is unlikely to be true.
+                           (Or prove me wrong and do it.)  */
+
+                        SV *const val = *subrv_p++;
+                        *svp++ = newSVsv(val);
+                    }
+
+                    SvREFCNT_dec(isa_lin);
+                    SvREFCNT_inc(retval);
+
+                    goto done;
+                }
                 av_push(seqs, (SV*)isa_lin);
             }
         }
         av_push(seqs, SvREFCNT_inc((SV*)isa));
+        tails = (HV*)sv_2mortal((SV*)newHV());
 
         /* This builds "heads", which as an array of integer array
            indices, one per seq, which point at the virtual "head"
@@ -146,15 +184,16 @@ __mro_linear_isa_c3(pTHX_ HV* stash, HV* cache, I32 level)
                 SV** seq_ptr = AvARRAY(seq) + 1;
                 while(seq_items--) {
                     SV* const seqitem = *seq_ptr++;
-                    HE* const he = hv_fetch_ent(tails, seqitem, 0, 0);
-                    if(!he) {
-                        if(!hv_store_ent(tails, seqitem, newSViv(1), 0)) {
-                            croak("failed to store value in hash");
-                        }
-                    }
-                    else {
+                    /* LVALUE fetch will create a new undefined SV if necessary
+                     */
+                    HE* const he = hv_fetch_ent(tails, seqitem, 1, 0);
+                    if(he) {
                         SV* const val = HeVAL(he);
+                        /* This will increment undef to 1, which is what we
+                           want for a newly created entry.  */
                         sv_inc(val);
+                    } else {
+                        croak("failed to store value in hash");
                     }
                 }
             }
@@ -260,6 +299,7 @@ __mro_linear_isa_c3(pTHX_ HV* stash, HV* cache, I32 level)
         av_push(retval, newSVpvn(stashname, stashname_len));
     }
 
+done:
     /* we don't want anyone modifying the cache entry but us,
        and we do so by replacing it completely */
     SvREADONLY_on(retval);
@@ -474,7 +514,7 @@ XS(XS_Class_C3_XS_nextcan)
             if (SvTYPE(candidate) == SVt_PVGV && (cand_cv = GvCV(candidate)) && !GvCVGEN(candidate)) {
                 SvREFCNT_dec(linear_av);
                 SvREFCNT_inc((SV*)cand_cv);
-                if (!hv_store_ent(nmcache, newSVsv(cachekey), (SV*)cand_cv, 0)) {
+                if (!hv_store_ent(nmcache, cachekey, (SV*)cand_cv, 0)) {
                     croak("failed to store value in hash");
                 }
                 XPUSHs(sv_2mortal(newRV_inc((SV*)cand_cv)));
@@ -484,7 +524,7 @@ XS(XS_Class_C3_XS_nextcan)
     }
 
     SvREFCNT_dec(linear_av);
-    if (!hv_store_ent(nmcache, newSVsv(cachekey), &PL_sv_undef, 0)) {
+    if (!hv_store_ent(nmcache, cachekey, &PL_sv_undef, 0)) {
         croak("failed to store value in hash");
     }
     if(throw_nomethod)