hv.h 
281 /* the number of keys (including any placeholers) */
282 #define XHvTOTALKEYS(xhv)       ((xhv)->xhv_keys)

289 #define HvKEYS(hv)              HvUSEDKEYS(hv)
290 #define HvUSEDKEYS(hv)          (HvTOTALKEYS(hv) - HvPLACEHOLDERS_
+get(hv))


293 #define HvPLACEHOLDERS_get(hv)  (SvMAGIC(hv) ? Perl_hv_placeholder
+s_get(aTHX_ (const HV *)hv) : 0)

[download]
hv.c 
2536 I32
2537 Perl_hv_placeholders_get(pTHX_ const HV *hv)
2538 {
2539     dVAR;
2540     MAGIC * const mg = mg_find((const SV *)hv, PERL_MAGIC_rhash);
2541 
2542     PERL_ARGS_ASSERT_HV_PLACEHOLDERS_GET;
2543 
2544     return mg ? mg->mg_len : 0;
2545 }

[download]
mg.c 
411 MAGIC*
412 Perl_mg_find(pTHX_ const SV *sv, int type)
413 {
414     PERL_UNUSED_CONTEXT;
415     if (sv) {
416         MAGIC *mg;
417         for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
418             if (mg->mg_type == type)
419                 return mg;
420         }
421     }
422     return NULL;
423 }

[download]

In reply to Re^5: What is the most efficient way to see if a hash is empty? by Anonymous Monk
in thread What is the most efficient way to see if a hash is empty? by ELISHEVA

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