S_share_hek_flags can revert to returning a HEK

[perl5.git] / hv.c

diff --git a/hv.c b/hv.c
index 556996e..3d2e589 100644 (file)
--- a/hv.c
+++ b/hv.c
@@ -126,19 +126,20 @@ Perl_free_tied_hv_pool(pTHX)
 HEK *
 Perl_hek_dup(pTHX_ HEK *source, CLONE_PARAMS* param)
 {
-    HE *shared = (HE*)ptr_table_fetch(PL_shared_hek_table, source);
+    HEK *shared = (HEK*)ptr_table_fetch(PL_ptr_table, source);
     (void)param;
 
     if (shared) {
        /* We already shared this hash key.  */
-       ++HeVAL(shared);
+       share_hek_hek(shared);
     }
     else {
-       shared = share_hek_flags(HEK_KEY(source), HEK_LEN(source),
-                                HEK_HASH(source), HEK_FLAGS(source));
-       ptr_table_store(PL_shared_hek_table, source, shared);
+       shared
+           = share_hek_flags(HEK_KEY(source), HEK_LEN(source),
+                             HEK_HASH(source), HEK_FLAGS(source));
+       ptr_table_store(PL_ptr_table, source, shared);
     }
-    return HeKEY_hek(shared);
+    return shared;
 }
 
 HE *
@@ -168,18 +169,19 @@ Perl_he_dup(pTHX_ HE *e, bool shared, CLONE_PARAMS* param)
        /* This is hek_dup inlined, which seems to be important for speed
           reasons.  */
        HEK *source = HeKEY_hek(e);
-       HE *shared = (HE*)ptr_table_fetch(PL_shared_hek_table, source);
+       HEK *shared = (HEK*)ptr_table_fetch(PL_ptr_table, source);
 
        if (shared) {
            /* We already shared this hash key.  */
-           ++HeVAL(shared);
+           share_hek_hek(shared);
        }
        else {
-           shared = share_hek_flags(HEK_KEY(source), HEK_LEN(source),
-                                    HEK_HASH(source), HEK_FLAGS(source));
-           ptr_table_store(PL_shared_hek_table, source, shared);
+           shared
+               = share_hek_flags(HEK_KEY(source), HEK_LEN(source),
+                                 HEK_HASH(source), HEK_FLAGS(source));
+           ptr_table_store(PL_ptr_table, source, shared);
        }
-       HeKEY_hek(ret) = HeKEY_hek(shared);
+       HeKEY_hek(ret) = shared;
     }
     else
        HeKEY_hek(ret) = save_hek_flags(HeKEY(e), HeKLEN(e), HeHASH(e),
@@ -685,8 +687,8 @@ S_hv_fetch_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
                    /* Need to swap the key we have for a key with the flags we
                       need. As keys are shared we can't just write to the
                       flag, so we share the new one, unshare the old one.  */
-                   HEK *new_hek = HeKEY_hek(share_hek_flags(key, klen, hash,
-                                                            masked_flags));
+                   HEK *new_hek = share_hek_flags(key, klen, hash,
+                                                  masked_flags);
                    unshare_hek (HeKEY_hek(entry));
                    HeKEY_hek(entry) = new_hek;
                }
@@ -790,7 +792,7 @@ S_hv_fetch_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
     /* share_hek_flags will do the free for us.  This might be considered
        bad API design.  */
     if (HvSHAREKEYS(hv))
-       HeKEY_hek(entry) = HeKEY_hek(share_hek_flags(key, klen, hash, flags));
+       HeKEY_hek(entry) = share_hek_flags(key, klen, hash, flags);
     else                                       /* gotta do the real thing */
        HeKEY_hek(entry) = save_hek_flags(key, klen, hash, flags);
     HeVAL(entry) = val;
@@ -1417,7 +1419,7 @@ Perl_newHVhv(pTHX_ HV *ohv)
                ent = new_HE();
                HeVAL(ent)     = newSVsv(HeVAL(oent));
                HeKEY_hek(ent)
-                    = shared ? HeKEY_hek(share_hek_flags(key, len, hash, flags))
+                    = shared ? share_hek_flags(key, len, hash, flags)
                              :  save_hek_flags(key, len, hash, flags);
                if (prev)
                    HeNEXT(prev) = ent;
@@ -2159,8 +2161,26 @@ S_unshare_hek_or_pvn(pTHX_ const HEK *hek, const char *str, I32 len, U32 hash)
     bool is_utf8 = FALSE;
     int k_flags = 0;
     const char *save = str;
+    struct shared_he *he = 0;
 
     if (hek) {
+       /* Find the shared he which is just before us in memory.  */
+       he = (struct shared_he *)(((char *)hek)
+                                 - STRUCT_OFFSET(struct shared_he,
+                                                 shared_he_hek));
+
+       /* Assert that the caller passed us a genuine (or at least consistent)
+          shared hek  */
+       assert (he->shared_he_he.hent_hek == hek);
+
+       LOCK_STRTAB_MUTEX;
+       if (he->shared_he_he.hent_val - 1) {
+           --he->shared_he_he.hent_val;
+           UNLOCK_STRTAB_MUTEX;
+           return;
+       }
+       UNLOCK_STRTAB_MUTEX;
+
         hash = HEK_HASH(hek);
     } else if (len < 0) {
         STRLEN tmplen = -len;
@@ -2183,9 +2203,10 @@ S_unshare_hek_or_pvn(pTHX_ const HEK *hek, const char *str, I32 len, U32 hash)
     /* assert(xhv_array != 0) */
     LOCK_STRTAB_MUTEX;
     first = oentry = &(HvARRAY(PL_strtab))[hash & (I32) HvMAX(PL_strtab)];
-    if (hek) {
+    if (he) {
+       const HE *const he_he = &(he->shared_he_he);
         for (entry = *oentry; entry; oentry = &HeNEXT(entry), entry = *oentry) {
-            if (HeKEY_hek(entry) != hek)
+            if (entry != he_he)
                 continue;
             found = 1;
             break;
@@ -2213,8 +2234,7 @@ S_unshare_hek_or_pvn(pTHX_ const HEK *hek, const char *str, I32 len, U32 hash)
                /* There are now no entries in our slot.  */
                 xhv->xhv_fill--; /* HvFILL(hv)-- */
            }
-            Safefree(HeKEY_hek(entry));
-            del_HE(entry);
+            Safefree(entry);
             xhv->xhv_keys--; /* HvKEYS(hv)-- */
         }
     }
@@ -2258,10 +2278,10 @@ Perl_share_hek(pTHX_ const char *str, I32 len, register U32 hash)
           flags |= HVhek_WASUTF8 | HVhek_FREEKEY;
     }
 
-    return HeKEY_hek(share_hek_flags (str, len, hash, flags));
+    return share_hek_flags (str, len, hash, flags);
 }
 
-STATIC HE *
+STATIC HEK *
 S_share_hek_flags(pTHX_ const char *str, I32 len, register U32 hash, int flags)
 {
     register XPVHV* xhv;
@@ -2299,11 +2319,35 @@ S_share_hek_flags(pTHX_ const char *str, I32 len, register U32 hash, int flags)
           If this is NULL, then we're the first entry for this slot, which
           means we need to increate fill.  */
        const HE *old_first = *oentry;
-       entry = new_HE();
-       HeKEY_hek(entry) = save_hek_flags(str, len, hash, flags_masked);
+       struct shared_he *new_entry;
+       HEK *hek;
+       char *k;
+
+       /* We don't actually store a HE from the arena and a regular HEK.
+          Instead we allocate one chunk of memory big enough for both,
+          and put the HEK straight after the HE. This way we can find the
+          HEK directly from the HE.
+       */
+
+       New(0, k, STRUCT_OFFSET(struct shared_he,
+                               shared_he_hek.hek_key[0]) + len + 2, char);
+       new_entry = (struct shared_he *)k;
+       entry = &(new_entry->shared_he_he);
+       hek = &(new_entry->shared_he_hek);
+
+       Copy(str, HEK_KEY(hek), len, char);
+       HEK_KEY(hek)[len] = 0;
+       HEK_LEN(hek) = len;
+       HEK_HASH(hek) = hash;
+       HEK_FLAGS(hek) = (unsigned char)flags_masked;
+
+       /* Still "point" to the HEK, so that other code need not know what
+          we're up to.  */
+       HeKEY_hek(entry) = hek;
        HeVAL(entry) = Nullsv;
        HeNEXT(entry) = *oentry;
        *oentry = entry;
+
        xhv->xhv_keys++; /* HvKEYS(hv)++ */
        if (!old_first) {                       /* initial entry? */
            xhv->xhv_fill++; /* HvFILL(hv)++ */
@@ -2318,7 +2362,7 @@ S_share_hek_flags(pTHX_ const char *str, I32 len, register U32 hash, int flags)
     if (flags & HVhek_FREEKEY)
        Safefree(str);
 
-    return entry;
+    return HeKEY_hek(entry);
 }
 
 I32 *