individual interpolation method performance tunings

this commit primarily uses frozen strings to reduce object creation during interpolation.
the :basename method now uses File.basename(file, ".*") rather than a Regexp. basename may be called multiple times.

lib/paperclip/interpolations.rb

@@ -47,7 +47,7 @@ module Paperclip
 
     # Returns the filename, the same way as ":basename.:extension" would.
     def filename attachment, style_name
-      [ basename(attachment, style_name), extension(attachment, style_name) ].reject(&:blank?).join(".")
+      [ basename(attachment, style_name), extension(attachment, style_name) ].delete_if(&:empty?).join(".".freeze)
     end
 
     # Returns the interpolated URL. Will raise an error if the url itself
@@ -95,7 +95,7 @@ module Paperclip
 
     # Returns the basename of the file. e.g. "file" for "file.jpg"
     def basename attachment, style_name
-      attachment.original_filename.gsub(/#{Regexp.escape(File.extname(attachment.original_filename))}\Z/, "")
+      File.basename(attachment.original_filename, ".*".freeze)
     end
 
     # Returns the extension of the file. e.g. "jpg" for "file.jpg"
@@ -103,7 +103,7 @@ module Paperclip
     # of the actual extension.
     def extension attachment, style_name
       ((style = attachment.styles[style_name.to_s.to_sym]) && style[:format]) ||
-        File.extname(attachment.original_filename).gsub(/\A\.+/, "")
+        File.extname(attachment.original_filename).sub(/\A\.+/, "".freeze)
     end
 
     # Returns the dot+extension of the file. e.g. ".jpg" for "file.jpg"
@@ -111,7 +111,7 @@ module Paperclip
     # of the actual extension. If the extension is empty, no dot is added.
     def dotextension attachment, style_name
       ext = extension(attachment, style_name)
-      ext.empty? ? "" : ".#{ext}"
+      ext.empty? ? ext : ".#{ext}"
     end
 
     # Returns an extension based on the content type. e.g. "jpeg" for
@@ -175,9 +175,9 @@ module Paperclip
     def id_partition attachment, style_name
       case id = attachment.instance.id
       when Integer
-        ("%09d" % id).scan(/\d{3}/).join("/")
+        ("%09d".freeze % id).scan(/\d{3}/).join("/".freeze)
       when String
-        id.scan(/.{3}/).first(3).join("/")
+        id.scan(/.{3}/).first(3).join("/".freeze)
       else
         nil
       end

lib/paperclip/storage/s3.rb

@@ -141,7 +141,7 @@ module Paperclip
             Proc.new do |style, attachment|
               permission  = (@s3_permissions[style.to_s.to_sym] || @s3_permissions[:default])
               permission  = permission.call(attachment, style) if permission.respond_to?(:call)
-              (permission == :public_read) ? 'http' : 'https'
+              (permission == :public_read) ? 'http'.freeze : 'https'.freeze
             end
           @s3_metadata = @options[:s3_metadata] || {}
           @s3_headers = {}
@@ -167,16 +167,16 @@ module Paperclip
         end
 
         Paperclip.interpolates(:s3_alias_url) do |attachment, style|
-          "#{attachment.s3_protocol(style, true)}//#{attachment.s3_host_alias}/#{attachment.path(style).gsub(%r{\A/}, "")}"
+          "#{attachment.s3_protocol(style, true)}//#{attachment.s3_host_alias}/#{attachment.path(style).gsub(%r{\A/}, "".freeze)}"
         end unless Paperclip::Interpolations.respond_to? :s3_alias_url
         Paperclip.interpolates(:s3_path_url) do |attachment, style|
-          "#{attachment.s3_protocol(style, true)}//#{attachment.s3_host_name}/#{attachment.bucket_name}/#{attachment.path(style).gsub(%r{\A/}, "")}"
+          "#{attachment.s3_protocol(style, true)}//#{attachment.s3_host_name}/#{attachment.bucket_name}/#{attachment.path(style).gsub(%r{\A/}, "".freeze)}"
         end unless Paperclip::Interpolations.respond_to? :s3_path_url
         Paperclip.interpolates(:s3_domain_url) do |attachment, style|
-          "#{attachment.s3_protocol(style, true)}//#{attachment.bucket_name}.#{attachment.s3_host_name}/#{attachment.path(style).gsub(%r{\A/}, "")}"
+          "#{attachment.s3_protocol(style, true)}//#{attachment.bucket_name}.#{attachment.s3_host_name}/#{attachment.path(style).gsub(%r{\A/}, "".freeze)}"
         end unless Paperclip::Interpolations.respond_to? :s3_domain_url
         Paperclip.interpolates(:asset_host) do |attachment, style|
-          "#{attachment.path(style).gsub(%r{\A/}, "")}"
+          "#{attachment.path(style).gsub(%r{\A/}, "".freeze)}"
         end unless Paperclip::Interpolations.respond_to? :asset_host
       end
 
@@ -197,7 +197,7 @@ module Paperclip
         host_name = @options[:s3_host_name]
         host_name = host_name.call(self) if host_name.is_a?(Proc)
 
-        host_name || s3_credentials[:s3_host_name] || "s3.amazonaws.com"
+        host_name || s3_credentials[:s3_host_name] || "s3.amazonaws.com".freeze
       end
 
       def s3_host_alias

spec/paperclip/interpolations_spec.rb

@@ -33,7 +33,7 @@ describe Paperclip::Interpolations do
 
   it "returns the basename of the file" do
     attachment = mock
-    attachment.expects(:original_filename).returns("one.jpg").times(2)
+    attachment.expects(:original_filename).returns("one.jpg").times(1)
     assert_equal "one", Paperclip::Interpolations.basename(attachment, :style)
   end
 
@@ -188,14 +188,14 @@ describe Paperclip::Interpolations do
   it "returns the filename as basename.extension" do
     attachment = mock
     attachment.expects(:styles).returns({})
-    attachment.expects(:original_filename).returns("one.jpg").times(3)
+    attachment.expects(:original_filename).returns("one.jpg").times(2)
     assert_equal "one.jpg", Paperclip::Interpolations.filename(attachment, :style)
   end
 
   it "returns the filename as basename.extension when format supplied" do
     attachment = mock
     attachment.expects(:styles).returns({style: {format: :png}})
-    attachment.expects(:original_filename).returns("one.jpg").times(2)
+    attachment.expects(:original_filename).returns("one.jpg").times(1)
     assert_equal "one.png", Paperclip::Interpolations.filename(attachment, :style)
   end