Default log device to binmode when it is a file

When the log device is initialized with a filename default to opening
the file using binmode.

Without binmode strings with incompatible encoding can't be written in
the file. This is very common in applications that log user provided
parameters.

We need to change the default because right now it is impossible to use
the built-in log rotation feature when you provide a File object to the
LogDevice, and if you provide a filename you can't have binmode.

lib/logger.rb

@@ -112,6 +112,9 @@
 #
 #      logger = Logger.new('logfile.log')
 #
+# *Note*: When a filename is use, the file is opened using the binary mode.
+# For more information see IO#binmode.
+#
 # 3. Create a logger for the specified file.
 #
 #      file = File.open('foo.log', File::WRONLY | File::APPEND)

lib/logger/log_device.rb

@@ -84,6 +84,7 @@ def set_dev(log)
       else
         @dev = open_logfile(log)
         @dev.sync = true
+        @dev.binmode
         @filename = log
       end
     end
@@ -101,6 +102,7 @@ def create_logfile(filename)
         logdev = File.open(filename, (File::WRONLY | File::APPEND | File::CREAT | File::EXCL))
         logdev.flock(File::LOCK_EX)
         logdev.sync = true
+        logdev.binmode
         add_log_header(logdev)
         logdev.flock(File::LOCK_UN)
       rescue Errno::EEXIST

test/logger/test_logdevice.rb

@@ -45,6 +45,7 @@ def test_initialize
     begin
       assert_file.exist?(@filename)
       assert_predicate(logdev.dev, :sync)
+      assert_predicate(logdev.dev, :binmode?)
       assert_equal(@filename, logdev.filename)
       logdev.write('hello')
     ensure
@@ -53,6 +54,8 @@ def test_initialize
     # create logfile whitch is already exist.
     logdev = d(@filename)
     begin
+      assert_predicate(logdev.dev, :sync)
+      assert_predicate(logdev.dev, :binmode?)
       logdev.write('world')
       logfile = File.read(@filename)
       assert_equal(2, logfile.split(/\n/).size)
@@ -103,6 +106,20 @@ class << (stderr = '')
     assert_equal "log writing failed. disk is full\n", stderr
   end
 
+  def test_write_binary_data
+    logdev = d(@filename)
+    begin
+      logdev.write("\x80".force_encoding("ASCII-8BIT"))
+      logfile = File.open(@filename)
+      logfile.binmode
+      logfile = logfile.read
+      assert_equal(2, logfile.split(/\n/).size)
+      assert_match(/^\x80$/, logfile)
+    ensure
+      logdev.close
+    end
+  end
+
   def test_close
     r, w = IO.pipe
     logdev = d(w)