output/driver.rb: add output plugin to reproduce

the original behavior of benchmark/driver.rb.
Probably I won't use this but this is requested by ko1.

Use this with:
make benchmark OPTS="-o driver"

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63937 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

benchmark/lib/benchmark_driver/output/driver.rb

@@ -0,0 +1,36 @@
+require 'benchmark_driver/output/simple'
+
+# This replicates the legacy benchmark/driver.rb behavior.
+class BenchmarkDriver::Output::Driver < BenchmarkDriver::Output::Simple
+  def initialize(*)
+    super
+    @stdout = $stdout
+    @strio  = StringIO.new
+    $stdout = IOMultiplexer.new(@stdout, @strio)
+  end
+
+  def with_benchmark(*)
+    super
+  ensure
+    logfile = "bmlog-#{Time.now.strftime('%Y%m%d-%H%M%S')}.#{$$}.log"
+    puts "\nLog file: #{logfile}"
+
+    $stdout = @stdout
+    File.write(logfile, @strio.tap(&:rewind).read)
+  end
+
+  class IOMultiplexer
+    def initialize(io1, io2)
+      @io1 = io1
+      @io2 = io2
+    end
+
+    [:write, :sync, :sync=, :puts, :print, :flush].each do |method|
+      define_method(method) do |*args|
+        @io1.send(method, *args)
+        @io2.send(method, *args)
+      end
+    end
+  end
+  private_constant :IOMultiplexer
+end