1 files changed, 36 insertions, 0 deletions
diff --git a/lib/irb/magic-file.rb b/lib/irb/magic-file.rb
new file mode 100644
index 0000000000..861262050e
--- /dev/null
+++ b/lib/irb/magic-file.rb
@@ -0,0 +1,36 @@
+module IRB
+  class << (MagicFile = Object.new)
+    # see parser_magic_comment in parse.y
+    ENCODING_SPEC_RE = %r"coding\s*[=:]\s*([[:alnum:]\-_]+)"
+
+    def open(path)
+      io = File.open(path, 'rb')
+      line = io.gets
+      line = io.gets if line[0,2] == "#!"
+      encoding = detect_encoding(line)
+      encoding ||= default_src_encoding
+      io.rewind
+      io.set_encoding(encoding, nil)
+
+      if block_given?
+        begin
+          return (yield io)
+        ensure
+          io.close
+        end
+      else
+        return io
+      end
+    end
+
+    private
+    def detect_encoding(line)
+      return unless line[0] == ?#
+      line = line[1..-1]
+      line = $1 if line[/-\*-\s*(.*?)\s*-*-$/]
+      return nil unless ENCODING_SPEC_RE =~ line
+      encoding = $1
+      return encoding.sub(/-(?:mac|dos|unix)/i, '')
+    end
+  end
+end