DataMapper bitwise comparison operator for MS SQL (tsql)

# Taken from http://pastebin.com/xWU62iT2
# See https://github.com/datamapper/dm-types/issues/44
# with modifications for sql server
module DataMapper
  class Query
    module Conditions
      # Tests whether the value in the record
      # has the specified bits set to true (bitwise and)
      class HasComparison < AbstractComparison
        slug :has

        def matches?(record)
          record_value = record_value(record)
          !record_value.nil? && (record_value & expected)
        end

        # @return [String]
        #
        # @see AbstractComparison#to_s
        #
        # @api private
        def comparator_string
          '&'
        end
      end # class HasFlagComparison
    end # module Conditions
  end # class Query
end # module DataMapper

module DataMapper
  module Adapters
    class DataObjectsAdapter < AbstractAdapter
      def comparison_operator(comparison)
        subject = comparison.subject
        value   = comparison.value

        case comparison.slug
        when :has    then has_operator(subject, value)
        when :eql    then equality_operator(subject, value)
        when :in     then include_operator(subject, value)
        when :regexp then regexp_operator(value)
        when :like   then like_operator(value)
        when :gt     then '>'
        when :lt     then '<'
        when :gte    then '>='
        when :lte    then '<='
        end
      end

      def has_operator(property, operand)
        "& #{operand} ="
      end
    end
  end
end