add slot function and make it work with read-only types

Author: radarroark

src/xitdb/array_list.clj

@@ -106,6 +106,10 @@
         (aset result len nil))
       result))
 
+  common/ISlot
+  (-slot [this]
+    (-> ral .cursor .slot))
+
   common/IUnwrap
   (-unwrap [this]
     ral)

src/xitdb/db.clj

@@ -62,6 +62,8 @@
     (common/-slot v)
     (conversion/v->slot! cursor v)))
 
+(def slot common/-slot)
+
 (defn xitdb-swap!
   "Starts a new transaction and calls `f` with the value at `base-keypath`.
   If `base-keypath` is nil, will use the root cursor.

src/xitdb/hash_map.clj

@@ -81,6 +81,10 @@
   (kv-reduce [this f init]
     (operations/map-kv-reduce rhm #(common/-read-from-cursor %) f init))
 
+  common/ISlot
+  (-slot [this]
+    (-> rhm .cursor .slot))
+
   common/IUnwrap
   (-unwrap [this]
     rhm)

src/xitdb/hash_set.clj

@@ -68,6 +68,10 @@
         (remove [_]
           (throw (UnsupportedOperationException. "XITDBHashSet iterator is read-only"))))))
 
+  common/ISlot
+  (-slot [this]
+    (-> rhs .cursor .slot))
+
   common/IUnwrap
   (-unwrap [_]
     rhs)

src/xitdb/linked_list.clj

@@ -86,6 +86,14 @@
         (aset result len nil))
       result))
 
+  common/ISlot
+  (-slot [this]
+    (-> rlal .cursor .slot))
+
+  common/IUnwrap
+  (-unwrap [_]
+    rlal)
+
   Object
   (toString [this]
     (pr-str (into [] this))))

src/xitdb/util/conversion.clj

@@ -103,6 +103,9 @@
   [v]
   (cond
 
+    (or (nil? v) (instance? Slot v))
+    v
+
     (string? v)
     (database-bytes v)
 
@@ -118,9 +121,6 @@
     (double? v)
     (Database$Float. v)
 
-    (nil? v)
-    nil
-
     (instance? java.time.Instant v)
     (database-bytes (str v) (fmt-tag-value :inst))