[PATCH v2 10/18] tools/xenstore: add hashtable_replace() function

[Juergen Gross <jgross@xxxxxxxx>]

For an effective way to replace a hashtable entry add a new function
hashtable_replace().

While at it let hashtable_add() fail if an entry with the specified
key does already exist.

This is in preparation to replace TDB with a more simple data storage.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 tools/xenstore/hashtable.c | 20 ++++++++++++++++++++
 tools/xenstore/hashtable.h | 16 ++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/tools/xenstore/hashtable.c b/tools/xenstore/hashtable.c
index 29c247f918..0c26a09567 100644
--- a/tools/xenstore/hashtable.c
+++ b/tools/xenstore/hashtable.c
@@ -160,6 +160,7 @@ static struct entry *hashtable_search_entry(const struct 
hashtable *h,
 
     return NULL;
 }
+
 int hashtable_add(struct hashtable *h, const void *k, void *v)
 {
     unsigned int index;
@@ -204,6 +205,25 @@ void *hashtable_search(const struct hashtable *h, const 
void *k)
     return e ? e->v : NULL;
 }
 
+int hashtable_replace(struct hashtable *h, const void *k, void *v)
+{
+    struct entry *e;
+
+    e = hashtable_search_entry(h, k);
+    if (!e)
+        return ENOENT;
+
+    if (h->flags & HASHTABLE_FREE_VALUE)
+    {
+        talloc_free(e->v);
+        talloc_steal(e, v);
+    }
+
+    e->v = v;
+
+    return 0;
+}
+
 void
 hashtable_remove(struct hashtable *h, const void *k)
 {
diff --git a/tools/xenstore/hashtable.h b/tools/xenstore/hashtable.h
index 792f6cda7b..214aea1b3d 100644
--- a/tools/xenstore/hashtable.h
+++ b/tools/xenstore/hashtable.h
@@ -51,6 +51,22 @@ create_hashtable(const void *ctx, const char *name,
 int
 hashtable_add(struct hashtable *h, const void *k, void *v);
 
+/*****************************************************************************
+ * hashtable_replace
+
+ * @name        hashtable_nsert
+ * @param   h   the hashtable to insert into
+ * @param   k   the key - hashtable claims ownership and will free on removal
+ * @param   v   the value - does not claim ownership
+ * @return      zero for successful insertion
+ *
+ * This function does check for an entry being present before replacing it
+ * with a new value.
+ */
+
+int
+hashtable_replace(struct hashtable *h, const void *k, void *v);
+
 /*****************************************************************************
  * hashtable_search
    
-- 
2.35.3