From bed82e10d3ab4af51958dd5c425b865bee5e9d99 Mon Sep 17 00:00:00 2001
From: Ben Sless <ben.sless@gmail.com>
Date: Tue, 24 Aug 2021 19:16:31 +0300
Subject: [PATCH] Add lightweight keyset wrapper

Saves on allocation and provides an immutable facade to underlying
regular set
---
 src/malli/core.cljc | 49 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 42 insertions(+), 7 deletions(-)

diff --git a/src/malli/core.cljc b/src/malli/core.cljc
index eeb69fdf4..2ab600023 100644
--- a/src/malli/core.cljc
+++ b/src/malli/core.cljc
@@ -278,14 +278,49 @@
           (-arange [^objects arr to]
             #?(:clj (let [-arr (object-array to)] (System/arraycopy arr 0 -arr 0 to) -arr)
                :cljs (.slice arr 0 to)))
+          #?(:clj
+             (-set-wrapper
+               [^java.util.Set s]
+               (reify
+                 Collection
+                 (size [_] (.size s))
+                 (containsAll [_ c] (.containsAll s c))
+                 clojure.lang.IPersistentSet
+                 (disjoin [_ key] (disj (set s) key))
+                 (contains [_ key] (.contains s key))
+                 (get [_ key] (when (.contains s key) key))
+                 clojure.lang.Counted
+                 (count [_] (.size s))
+                 clojure.lang.IPersistentCollection
+                 (cons [_ o] (.cons (set s) o))
+                 (empty [_] #{})
+                 (equiv [_ o]
+                   (if (instance? java.util.Set o)
+                     (if (== (.size s) (.size ^Collection o))
+                       (.containsAll s o)
+                       false)
+                     false))
+                 clojure.lang.Seqable
+                 (seq [_] (seq s))
+                 clojure.lang.IFn
+                 (invoke [_ o] (when (.contains s o) o))
+                 Iterable
+                 (iterator [_] (.iterator s)))))
           (-keyset []
-            (let [data (volatile! #{})]
-              (fn
-                ([] @data)
-                ([k] (let [old @data]
-                       (vswap! data conj k)
-                       (when (= old @data)
-                         (-fail! ::non-distinct-entry-keys {:keys old, :key k})))))))]
+            #?(:clj
+               (let [data (java.util.HashSet.)]
+                 (fn
+                   ([] (-set-wrapper data))
+                   ([k] (when-not (.add data k)
+                          (-fail! ::non-distinct-entry-keys {:keys (seq data), :key k})))))
+               :cljs
+               (let [data (volatile! #{})]
+                 (fn
+                   ([] @data)
+                   ([k] (let [old @data]
+                          (vswap! data conj k)
+                          (when (= old @data)
+                            (-fail! ::non-distinct-entry-keys {:keys old, :key k}))))))))]
     (let [n (count children)
           -children (object-array n)
           -entries (object-array n)