dict.c: introduce dictUnlink().

Notes by @antirez:

This patch was picked from a larger commit by Oran and adapted to change
the API a bit. The basic idea is to avoid double lookups when there is
to use the value of the deleted entry.

BEFORE:

    entry = dictFind( ... ); /* 1st lookup. */
    /* Do somethjing with the entry. */
    dictDelete(...);         /* 2nd lookup. */

AFTER:

    entry = dictUnlink( ... ); /* 1st lookup. */
    /* Do somethjing with the entry. */
    dictFreeUnlinkedEntry(entry); /* No lookups!. */

1 files changed, 2 insertions, 1 deletions

diff --git a/src/dict.h b/src/dict.h
index 739de68ef..406fa36d8 100644
--- a/src/dict.h
+++ b/src/dict.h
@@ -154,7 +154,8 @@ dictEntry *dictAddRaw(dict *d, void *key, dictEntry **existing);
 int dictReplace(dict *d, void *key, void *val);
 dictEntry *dictReplaceRaw(dict *d, void *key);
 int dictDelete(dict *d, const void *key);
-int dictDeleteNoFree(dict *d, const void *key);
+dictEntry *dictUnlink(dict *ht, const void *key);
+void dictFreeUnlinkedEntry(dict *d, dictEntry *he);
 void dictRelease(dict *d);
 dictEntry * dictFind(dict *d, const void *key);
 void *dictFetchValue(dict *d, const void *key);