tdb: add utility function check_merge_ptr_with_left_record()

Variant of check_merge_with_left_record() that reads the record
itself if necessary.

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>

diff --git a/lib/tdb/common/freelist.c b/lib/tdb/common/freelist.c
index 47d63011148de653e74232f6c26ab516ce8592ea..9b508757ebc93dffc821d31bf779d70331c35c56 100644 (file)
--- a/lib/tdb/common/freelist.c
+++ b/lib/tdb/common/freelist.c
@@ -240,6 +240,59 @@ static int check_merge_with_left_record(struct tdb_context *tdb,
        return 1;
 }
 
+/**
+ * Check whether the record left of a given freelist record is
+ * also a freelist record, and if so, merge the two records.
+ *
+ * Return code:
+ *  -1 upon error
+ *   0 if left was not a free record
+ *   1 if left was free and successfully merged.
+ *
+ * In this variant, the input record is specified just as the pointer
+ * and is read from the database if needed.
+ *
+ * next_ptr will contain the original record's next pointer after
+ * successful merging (which will be lost after merging), so that
+ * the caller can update the last pointer.
+ */
+static int check_merge_ptr_with_left_record(struct tdb_context *tdb,
+                                           tdb_off_t rec_ptr,
+                                           tdb_off_t *next_ptr)
+{
+       tdb_off_t left_ptr;
+       struct tdb_record rec, left_rec;
+       int ret;
+
+       ret = read_record_on_left(tdb, rec_ptr, &left_ptr, &left_rec);
+       if (ret != 0) {
+               return 0;
+       }
+
+       if (left_rec.magic != TDB_FREE_MAGIC) {
+               return 0;
+       }
+
+       /* It's free - expand to include it. */
+
+       ret = tdb->methods->tdb_read(tdb, rec_ptr, &rec,
+                                    sizeof(rec), DOCONV());
+       if (ret != 0) {
+               return -1;
+       }
+
+       ret = merge_with_left_record(tdb, left_ptr, &left_rec, &rec);
+       if (ret != 0) {
+               return -1;
+       }
+
+       if (next_ptr != NULL) {
+               *next_ptr = rec.next;
+       }
+
+       return 1;
+}
+
 /**
  * Add an element into the freelist.
  *