CLJS-3141: Improve perf of cljs.source-map.base64/encode

Author: mfikes

src/main/clojure/cljs/source_map/base64.clj

@@ -12,11 +12,14 @@
 (def char->int (zipmap chars64 (range 0 64)))
 (def int->char (zipmap (range 0 64) chars64))
 
-(defn encode [n]
-  (let [e (find int->char n)]
-   (if e
-     (second e)
-     (throw (Error. (str "Must be between 0 and 63: " n))))))
+(defn encode [^long n]
+  (case n
+    0 \A 1 \B 2 \C 3 \D 4 \E 5 \F 6 \G 7 \H 8 \I 9 \J 10 \K 11 \L 12 \M
+    13 \N 14 \O 15 \P 16 \Q 17 \R 18 \S 19 \T 20 \U 21 \V 22 \W 23 \X 24 \Y 25 \Z
+    26 \a 27 \b 28 \c 29 \d 30 \e 31 \f 32 \g 33 \h 34 \i 35 \j 36 \k 37 \l 38 \m
+    39 \n 40 \o 41 \p 42 \q 43 \r 44 \s 45 \t 46 \u 47 \v 48 \w 49 \x 50 \y 51 \z
+    52 \0 53 \1 54 \2 55 \3 56 \4 57 \5 58 \6 59 \7 60 \8 61 \9 62 \+ 63 \/
+    (throw (Error. (str "Must be between 0 and 63: " n)))))
 
 (defn ^Character decode [c]
   (let [e (find char->int c)]

src/test/clojure/cljs/source_map/base64_tests.clj

@@ -0,0 +1,17 @@
+;; Copyright (c) Rich Hickey. All rights reserved.
+;; The use and distribution terms for this software are covered by the
+;; Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
+;; which can be found in the file epl-v10.html at the root of this distribution.
+;; By using this software in any fashion, you are agreeing to be bound by
+;; the terms of this license.
+;; You must not remove this notice, or any other, from this software.
+
+(ns cljs.source-map.base64-tests
+  (:require
+    [clojure.test :refer [deftest is]]
+    [cljs.source-map.base64 :as base64]))
+
+(deftest encode-test
+  (doseq [n (range 64)]
+    (is (= (get base64/int->char n) (base64/encode n))))
+  (is (thrown-with-msg? Error #"Must be between 0 and 63: 64" (base64/encode 64))))