WindowsFile: Fix incorrect error message

It passes win32 error codes to SystemCallError so that it doesn't show
correct message for them. For example when ERROR_SHARING_VIOLATION(32)
of win32 occurs, it shows Errno::EPIPE(32).

Signed-off-by: Takuro Ashie <ashie@clear-code.com>

lib/fluent/plugin/file_wrapper.rb

@@ -46,6 +46,33 @@ def s.ino; @ino; end
     end
   end
 
+  class Win32Error < StandardError
+    require 'windows/error'
+    include Windows::Error
+
+    attr_reader :errcode
+
+    def initialize(errcode)
+      @errcode = errcode
+    end
+
+    def format_english_message(errcode)
+      buf = 0.chr * 260
+      flags = FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ARGUMENT_ARRAY
+      english_lang_id = 1033 # The result of MAKELANDID(LANG_ENGLISH, SUBLANG_ENGLISH_US)
+      FormatMessageA.call(flags, 0, errcode, english_lang_id, buf, buf.size, 0)
+      buf
+    end
+
+    def message
+      "code: #{@errcode}, #{format_english_message(@errcode)}"
+    end
+
+    def ==(other)
+      @errcode == other.errcode
+    end
+  end
+
   # To open and get stat with setting FILE_SHARE_DELETE
   class WindowsFile
     require 'windows/file'
@@ -81,7 +108,7 @@ def initialize(path, mode='r', sharemode=FILE_SHARE_READ|FILE_SHARE_WRITE|FILE_S
         if err == ERROR_FILE_NOT_FOUND || err == ERROR_PATH_NOT_FOUND || err == ERROR_ACCESS_DENIED
           raise SystemCallError.new(2)
         end
-        raise SystemCallError.new(err)
+        raise Win32Error.new(err)
       end
     end
 

test/plugin/test_file_wrapper.rb

@@ -0,0 +1,72 @@
+require_relative '../helper'
+require 'fluent/plugin/file_wrapper'
+
+class FileWrapperTest < Test::Unit::TestCase
+  require 'windows/file'
+  include Windows::File
+
+  TMP_DIR = File.dirname(__FILE__) + "/../tmp/file_wrapper#{ENV['TEST_ENV_NUMBER']}"
+
+  def setup
+    FileUtils.mkdir_p(TMP_DIR)
+  end
+
+  def teardown
+    FileUtils.rm_rf(TMP_DIR)
+  end
+
+  sub_test_case 'Win32Error' do
+    test 'equal' do
+      assert_equal(Fluent::Win32Error.new(32),
+                   Fluent::Win32Error.new(32))
+    end
+
+    test 'not equal' do
+      assert_not_equal(Fluent::Win32Error.new(2),
+                       Fluent::Win32Error.new(32))
+    end
+  end
+
+  sub_test_case 'WindowsFile exceptions' do
+    test 'nothing raised' do
+      begin
+        path = "#{TMP_DIR}/test_file_wrapper.txt"
+        file1 = file2 = nil
+        file1 = File.open(path, "wb") do |f|
+        end
+        assert_nothing_raised do
+          file2 = Fluent::WindowsFile.new(path)
+        ensure
+          file2.close
+        end
+      ensure
+        file1.close if file1
+      end
+    end
+
+    test 'Errno::ENOENT raised' do
+      path = "#{TMP_DIR}/nofile.txt"
+      file = nil
+      assert_raise(SystemCallError.new(2)) do
+        file = Fluent::WindowsFile.new(path)
+      ensure
+        file.close if file
+      end
+    end
+
+    test 'ERROR_SHARING_VIOLATION raised' do
+      begin
+        path = "#{TMP_DIR}/test_file_wrapper.txt"
+        file1 = file2 = nil
+        file1 = File.open(path, "wb")
+        assert_raise(Fluent::Win32Error.new(32)) do
+          file2 = Fluent::WindowsFile.new(path, 'r', FILE_SHARE_READ)
+        ensure
+          file2.close if file2
+        end
+      ensure
+        file1.close if file1
+      end
+    end
+  end
+end if Fluent.windows?