Optimize URI escaping

The URI::Parser#escape method is a general use method that has to deal
with a variety of input however our use of it is limited in scope so
we can increase the performance by implementing our specific needs
within ActionDispatch::Journey::Router::Utils directly.

If there is no encoding required then there is no change in performance
or number of objects allocated, but for each character that needs to be
encoded we save five object allocations and gain a performance boost.
The performance boost seen varies from 20% when there is one character
to over 50% when encoding ten characters.

actionpack/lib/action_dispatch/journey/router/utils.rb

-require 'uri'
-
 module ActionDispatch
   module Journey # :nodoc:
     class Router # :nodoc:
@@ -25,31 +23,58 @@ def self.normalize_path(path)
 
         # URI path and fragment escaping
         # http://tools.ietf.org/html/rfc3986
-        module UriEscape # :nodoc:
-          # Symbol captures can generate multiple path segments, so include /.
-          reserved_segment  = '/'
-          reserved_fragment = '/?'
-          reserved_pchar    = ':@&=+$,;'
-
-          safe_pchar    = "#{URI::REGEXP::PATTERN::UNRESERVED}#{reserved_pchar}"
-          safe_segment  = "#{safe_pchar}#{reserved_segment}"
-          safe_fragment = "#{safe_pchar}#{reserved_fragment}"
-          UNSAFE_SEGMENT  = Regexp.new("[^#{safe_segment}]", false).freeze
-          UNSAFE_FRAGMENT = Regexp.new("[^#{safe_fragment}]", false).freeze
+        class UriEncoder # :nodoc:
+          ENCODE   = "%%%02X".freeze
+          ENCODING = Encoding::US_ASCII
+          EMPTY    = "".force_encoding(ENCODING).freeze
+          DEC2HEX  = (0..255).to_a.map{ |i| ENCODE % i }.map{ |s| s.force_encoding(ENCODING) }
+
+          ALPHA = "a-zA-Z".freeze
+          DIGIT = "0-9".freeze
+          UNRESERVED = "#{ALPHA}#{DIGIT}\\-\\._~".freeze
+          SUB_DELIMS = "!\\$&'\\(\\)\\*\\+,;=".freeze
+
+          ESCAPED  = /%[a-zA-Z0-9]{2}/.freeze
+
+          FRAGMENT = /[^#{UNRESERVED}#{SUB_DELIMS}:@\/\?]/.freeze
+          PATH     = /[^#{UNRESERVED}#{SUB_DELIMS}:@\/]/.freeze
+
+          def escape_fragment(fragment)
+            escape(fragment, FRAGMENT)
+          end
+
+          def escape_path(path)
+            escape(path, PATH)
+          end
+
+          def unescape_uri(uri)
+            uri.gsub(ESCAPED) { [$&[1, 2].hex].pack('C') }.force_encoding(uri.encoding)
+          end
+
+          protected
+            def escape(component, pattern)
+              component.gsub(pattern){ |unsafe| percent_encode(unsafe) }.force_encoding(ENCODING)
+            end
+
+            def percent_encode(unsafe)
+              safe = EMPTY.dup
+              unsafe.each_byte { |b| safe << DEC2HEX[b] }
+              safe
+            end
         end
 
-        Parser = URI::Parser.new
+        ENCODER = UriEncoder.new
 
         def self.escape_path(path)
-          Parser.escape(path.to_s, UriEscape::UNSAFE_SEGMENT)
+          ENCODER.escape_path(path.to_s)
         end
 
         def self.escape_fragment(fragment)
-          Parser.escape(fragment.to_s, UriEscape::UNSAFE_FRAGMENT)
+          ENCODER.escape_fragment(fragment.to_s)
         end
 
         def self.unescape_uri(uri)
-          Parser.unescape(uri)
+          ENCODER.unescape_uri(uri)
         end
       end
     end