Initial Revision

[ohcount] / ext / ohcount_native / escape_helper.rb

module EscapeHelper
        # From Ruby, we are generating C code which will call pcre.
        #
        # This means that characters that are significant to the C parser or the pcre regular
        # expression parser must be escaped multiple times, once for each layer of code that
        # must evaluate it.
        #
        # For instance, suppose you want to represent a literal backslash in a regular expression.
        # That means we must pass TWO backslashes (\\) to pcre.
        # The two backslashes will be stored in a C string constant -- and to express two backslashes
        # in a C string constant, we must use FOUR backslashes (\\\\).
        # It gets even better. To express these four backslashes in Ruby, we must use a literal string
        # that has EIGHT backslashes!
        #
        # This helper method exists to wade through all of this mess, adding the correct number of
        # backslashes to many types of special characters.
        #
        # Some examples:
        #
        #   e('/*')     -> /\\\*      # * must be escaped because it has meaning to regular expression parser
        #   e('"')      -> \\\"       # " must be escaped because it has meaning to the C string parser
        #   e('\\')     -> \\\\\\\\   # \ must be multiply escaped because it has meaning to both C and regex
        #
        # If you really want to pass a regular expression operator to pcre (for instance, you want . to be
        # the wildcard operator, not a literal period), then you should NOT use this helper, and you'll have to
        # sort out your escaping on your own.
        #
        # Someday we'll move this whole product over to Regel and get rid of all this craziness.
        def e(string)
                string.gsub(/\\/,'\\\\' * 4).gsub(/([\+\-\?\.\*\(\)\[\]])/, '\\\\' * 2 + '\1').gsub('"', '\\\\"')
        end
end