Merge pull request #6 from jcmfernandes/avoid-obj-allocation

Avoid unnecessary string duplication in .urlsafe_decode64

Author: hsbt

.gitignore

@@ -6,3 +6,4 @@
 /pkg/
 /spec/reports/
 /tmp/
+Gemfile.lock

Gemfile

@@ -1,4 +1,4 @@
 source "https://rubygems.org"
 
 gem "rake"
-gem "minitest"
+gem "test-unit"

lib/base64.rb

@@ -99,9 +99,11 @@ def urlsafe_decode64(str)
     # NOTE: RFC 4648 does say nothing about unpadded input, but says that
     # "the excess pad characters MAY also be ignored", so it is inferred that
     # unpadded input is also acceptable.
-    str = str.tr("-_", "+/")
     if !str.end_with?("=") && str.length % 4 != 0
       str = str.ljust((str.length + 3) & ~3, "=")
+      str.tr!("-_", "+/")
+    else
+      str = str.tr("-_", "+/")
     end
     strict_decode64(str)
   end