normal	2017-05-22 08:52:08 +0900 (Mon, 22 May 2017)

  New Revision: 58840

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=58840

  Log:
    lib/net/protocol: clear short-lived read buffer
    
    Using a parallel Net::HTTP downloader, this reduced memory usage
    from around 120MB to 50MB on my 32-bit x86 system.
    
    * lib/net/protocol.rb (rbuf_fill): clear temporary buffer
    
    Test script I used:
    
      require 'net/http'
      require 'uri'
      require 'digest/sha1'
      url = 'http://80x24.org/git-i-forgot-to-pack/objects/pack/pack-97b25a76c03b489d4cbbd85b12d0e1ad28717e55.idx'
      uri = URI(url)
      use_ssl = "https" == uri.scheme
      thrs = 30.times.map do
        Thread.start do
          cur = Thread.current.object_id
          Net::HTTP.start(uri.host, uri.port, use_ssl: use_ssl) do |http|
            req = Net::HTTP::Get.new(uri)
            http.request(req) do |res|
              dig = Digest::SHA1.new
              res.read_body do |buf|
                dig.update(buf)
                #buf.clear # most Ruby programmers don't do this :<
              end
              warn "#{Time.now} #{cur} #{dig.hexdigest}\n"
            end
          end
          :done
        end
      end
    
      p thrs.map(&:value)

  Modified files:
    trunk/lib/net/protocol.rb
Index: lib/net/protocol.rb
===================================================================
--- lib/net/protocol.rb	(revision 58839)
+++ lib/net/protocol.rb	(revision 58840)
@@ -171,7 +171,9 @@ module Net # :nodoc: https://github.com/ruby/ruby/blob/trunk/lib/net/protocol.rb#L171
     def rbuf_fill
       case rv = @io.read_nonblock(BUFSIZE, exception: false)
       when String
-        return @rbuf << rv
+        @rbuf << rv
+        rv.clear
+        return
       when :wait_readable
         @io.to_io.wait_readable(@read_timeout) or raise Net::ReadTimeout
         # continue looping

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