webrick/httpresponse: minor cleanups to reduce memory use

I never knew "format" was a global method alias for "sprintf";
so it was confusing to me.  Normally, one would use "sprintf"
since it's also available in many other languages, but
Integer#to_s avoids parsing a format string so it's less
bug-prone.

Furthermore, favor string interpolation over String#<< since it
is easier for the VM to optimize memory allocation (as in r60320).
Interpolation also reduces method calls and memory overhead
for inline method cache.

Finally, ensure we clear all short-lived buffers for body
responses.  A similar change was made and measured for Net::*
in r58840 showing a large memory reduction on some workloads.

* webrick/httpresponse.rb (send_body_io): favor String#to_s,
  reduce method calls for String#<<,
  clear `buf' when done,
  avoid extra String#bytesize calls

* (send_body_string): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60586 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/webrick/httpresponse.rb

@@ -396,19 +396,18 @@ module WEBrick
         if @request_method == "HEAD"
           # do nothing
         elsif chunked?
+          buf  = ''
           begin
-            buf  = ''
-            data = ''
-            while true
-              @body.readpartial( @buffer_size, buf ) # there is no need to clear buf?
-              data << format("%x", buf.bytesize) << CRLF
-              data << buf << CRLF
-              _write_data(socket, data)
-              data.clear
-              @sent_size += buf.bytesize
-            end
-          rescue EOFError # do nothing
-          end
+            @body.readpartial(@buffer_size, buf)
+            size = buf.bytesize
+            data = "#{size.to_s(16)}#{CRLF}#{buf}#{CRLF}"
+            _write_data(socket, data)
+            data.clear
+            @sent_size += size
+          rescue EOFError
+            break
+          end while true
+          buf.clear
           _write_data(socket, "0#{CRLF}#{CRLF}")
         else
           size = @header['content-length'].to_i
@@ -427,11 +426,11 @@ module WEBrick
         body ? @body.bytesize : 0
         while buf = @body[@sent_size, @buffer_size]
           break if buf.empty?
-          data = ""
-          data << format("%x", buf.bytesize) << CRLF
-          data << buf << CRLF
+          size = buf.bytesize
+          data = "#{size.to_s(16)}#{CRLF}#{buf}#{CRLF}"
+          buf.clear
           _write_data(socket, data)
-          @sent_size += buf.bytesize
+          @sent_size += size
         end
         _write_data(socket, "0#{CRLF}#{CRLF}")
       else