[PATCH 3/5] use frozen string literals for Ruby 2.1+

[Eric Wong <e@80x24.org>]

Constant lookups (even with caching) have extra size and speed
costs compared to just using frozen string literals.  This slows
down performance on older Rubies (even if they become
unsupported upstream), but newest C Ruby takes priority
(currently 2.3).
---
 lib/http_spew/content_md5.rb |  4 +---
 lib/http_spew/headers.rb     | 23 +++++++----------------
 2 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/lib/http_spew/content_md5.rb b/lib/http_spew/content_md5.rb
index 1c5be88..a999111 100644
--- a/lib/http_spew/content_md5.rb
+++ b/lib/http_spew/content_md5.rb
@@ -7,8 +7,6 @@ class HTTP_Spew::ContentMD5
   attr_reader :content_md5
   attr_reader :bytes_digested
 
-  CRLF = "\r\n" # :nodoc:
-
   def initialize(env, input = env["rack.input"])
     if trailer = env["HTTP_TRAILER"]
       unless trailer.split(/\s*,\s*/).grep(/\AContent-MD5\z/i)[0]
@@ -41,7 +39,7 @@ class HTTP_Spew::ContentMD5
             @bytes_digested += n
             wr.write("#{n.to_s(16)}\r\n")
             digest.update(buf)
-            wr.write(buf << CRLF)
+            wr.write(buf << "\r\n".freeze)
           end while input.read(0x4000, buf)
         end
         if expect_len && expect_len.to_i != @bytes_digested
diff --git a/lib/http_spew/headers.rb b/lib/http_spew/headers.rb
index da34c03..6f6f4d0 100644
--- a/lib/http_spew/headers.rb
+++ b/lib/http_spew/headers.rb
@@ -1,18 +1,10 @@
 # -*- encoding: binary -*-
 module HTTP_Spew::Headers
-  # :stopdoc:
-  REQUEST_METHOD = "REQUEST_METHOD"
-  REQUEST_URI = "REQUEST_URI"
-  CRLF = "\r\n"
-  QUERY_STRING = "QUERY_STRING"
-  PATH_INFO = "PATH_INFO"
-  CONTENT_TYPE = "CONTENT_TYPE" # specified by Rack to be !/^HTTP_/
-  # :startdoc:
 
   # regenerates the request_uri from a Rack +env+
   def request_uri(env)
-    qs = env[QUERY_STRING]
-    qs.size == 0 ? env[PATH_INFO] : "#{env[PATH_INFO]}?#{qs}"
+    qs = env['QUERY_STRING']
+    qs.size == 0 ? env['PATH_INFO'] : "#{env['PATH_INFO']}?#{qs}"
   end
   module_function :request_uri
 
@@ -27,26 +19,25 @@ module HTTP_Spew::Headers
   #
   #   buf, input = env_to_headers(env, input)
   def env_to_headers(env, input)
-    req = "#{env[REQUEST_METHOD]} " \
-          "#{env[REQUEST_URI] || request_uri(env)} HTTP/1.1\r\n" \
+    req = "#{env['REQUEST_METHOD']} " \
+          "#{env['REQUEST_URI'] || request_uri(env)} HTTP/1.1\r\n" \
           "Connection: close\r\n"
-    uscore, dash = "_", "-"
     env.each do |key,value|
       %r{\AHTTP_(\w+)\z} =~ key or next
       key = $1
       %r{\A(?:VERSION|EXPECT|TRANSFER_ENCODING|CONNECTION|KEEP_ALIVE)\z}x =~
         key and next
 
-      key.tr!(uscore, dash)
+      key.tr!('_'.freeze, '-'.freeze)
       req << "#{key}: #{value}\r\n"
     end
     if input
       req << (input.respond_to?(:size) ?
              "Content-Length: #{input.size}\r\n" :
              "Transfer-Encoding: chunked\r\n")
-      ct = env[CONTENT_TYPE] and req << "Content-Type: #{ct}\r\n"
+      ct = env['CONTENT_TYPE'] and req << "Content-Type: #{ct}\r\n"
     end
-    req << CRLF
+    req << "\r\n".freeze
     String === input ? (req << input) : [ req, input ]
   end
   module_function :env_to_headers
-- 
EW