webrick/httpresponse: IO.copy_stream for regular files

Remove the redundant _send_file method since its functionality
is unnecessary with IO.copy_stream.  IO.copy_stream also allows
the use of sendfile under some OSes to speed up copies to
non-TLS sockets.

Testing with "curl >/dev/null" and "ruby -run -e httpd" to
read a 1G file over Linux loopback reveals a reduction from
around ~0.770 to ~0.490 seconds on the client side.

* lib/webrick/httpresponse.rb (send_body_io): use IO.copy_stream
  (_send_file): remove
  [Feature #14237]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62954 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/webrick/httpresponse.rb

@@ -410,9 +410,9 @@ module WEBrick
           buf.clear
           socket.write("0#{CRLF}#{CRLF}")
         else
-          size = @header['content-length'].to_i
-          _send_file(socket, @body, 0, size)
-          @sent_size = size
+          size = @header['content-length']
+          size = size.to_i if size
+          @sent_size = IO.copy_stream(@body, socket, size)
         end
       ensure
         @body.close
@@ -474,27 +474,6 @@ module WEBrick
       alias :<< :write
     end
 
-    def _send_file(output, input, offset, size)
-      while offset > 0
-        sz = @buffer_size < size ? @buffer_size : size
-        buf = input.read(sz)
-        offset -= buf.bytesize
-      end
-
-      if size == 0
-        while buf = input.read(@buffer_size)
-          output.write(buf)
-        end
-      else
-        while size > 0
-          sz = @buffer_size < size ? @buffer_size : size
-          buf = input.read(sz)
-          output.write(buf)
-          size -= buf.bytesize
-        end
-      end
-    end
-
     # preserved for compatibility with some 3rd-party handlers
     def _write_data(socket, data)
       socket << data