1 files changed, 70 insertions, 0 deletions
diff --git a/lib/rdoc/markup/attributes.rb b/lib/rdoc/markup/attributes.rb
new file mode 100644
index 0000000000..3423f10ca7
--- /dev/null
+++ b/lib/rdoc/markup/attributes.rb
@@ -0,0 +1,70 @@
+##
+# We manage a set of attributes.  Each attribute has a symbol name and a bit
+# value.
+
+class RDoc::Markup::Attributes
+
+  ##
+  # The special attribute type.  See RDoc::Markup#add_special
+
+  attr_reader :special
+
+  ##
+  # Creates a new attributes set.
+
+  def initialize
+    @special = 1
+
+    @name_to_bitmap = [
+      [:_SPECIAL_, @special],
+    ]
+
+    @next_bitmap = @special << 1
+  end
+
+  ##
+  # Returns a unique bit for +name+
+
+  def bitmap_for name
+    bitmap = @name_to_bitmap.assoc name
+
+    unless bitmap then
+      bitmap = @next_bitmap
+      @next_bitmap <<= 1
+      @name_to_bitmap << [name, bitmap]
+    else
+      bitmap = bitmap.last
+    end
+
+    bitmap
+  end
+
+  ##
+  # Returns a string representation of +bitmap+
+
+  def as_string bitmap
+    return 'none' if bitmap.zero?
+    res = []
+
+    @name_to_bitmap.each do |name, bit|
+      res << name if (bitmap & bit) != 0
+    end
+
+    res.join ','
+  end
+
+  ##
+  # yields each attribute name in +bitmap+
+
+  def each_name_of bitmap
+    return enum_for __method__, bitmap unless block_given?
+
+    @name_to_bitmap.each do |name, bit|
+      next if bit == @special
+
+      yield name.to_s if (bitmap & bit) != 0
+    end
+  end
+
+end
+