[ragel-users] Help beginning with Ragel

Iñaki Baz Castillo ibc at aliax.net
Mon Jan 26 22:34:42 UTC 2009

Hi, I'm beginning with Ragel. For now I've readed the documentation and try to 
do some easy examples with Ruby host language (no C extensions for now).

I just want to parse a SIP URI like this:

  sip:alice at mydomain.org

and extract the following data into a Ruby SIP_URI class instance:

  @protocol => "sip"
  @user => "alice"
  @host => "mydomain.org"

I've already done this easy parser but I don't know how to extract the parsed 
data into the Ruby attributes. The code I've done for now is:

class SIP_URI

	attr_accessor :protocol, :user, :host

	def initialize
		@protocol = ""
		@user = ""
		@host = ""

	def to_s
		#puts @protocol.to_s + ':' + @user.to_s + '@' + @host.to_s
		# puts "Not implemented yet..."

@my_sip_uri = SIP_URI.new

	machine sip_uri;

	protocol = ('sip'|'sips');
	user = [a-zA-Z0-9]+;
	host = [a-zA-Z0-9]+;

	main := protocol ':' user '@' host;

%% write data;

def run_machine(data)
	puts "Running Ragel the state machine with input #{data}..."

	# Initialization
	data = data.unpack("c*") if data.is_a?(String)
	p = 0
	pe = data.length
	tag = nil

	%% write init;
	%% write exec;

	puts "Finished. The state of the machine is: #{cs}"
	puts "p: #{p} pe: #{pe}"

run_machine ARGV[0]

puts @my_sip_uri

It works, of course, but it's not very useful as it is now :)

To get the parsed data fragments I've readed about the usage of:

	action _tag { mark_tag = p }
	action tag { tag = data[mark_tag..p-1] }
	machine sip_uri;

	protocol = ('sip'|'sips') >_tag %tag ;
	user = [a-zA-Z0-9]+ >_tag %tag ;
	host = [a-zA-Z0-9]+ >_tag %tag ;

	main := protocol ':' user '@' host;

I understand that "tag" will be a data array fragment starting by "p" and 
finishing in each found expression. But I have no idea (and have found no 
doc) about how to get that info into Ruby variables.

If I compile the above code with the new block I get an error anyway:

  example02.rl:21:2: there is no previous specification name
  example02.rl:28: action lookup of "_tag" failed
  example02.rl:28: action lookup of "tag" failed

In the documentation I read about a variable "ts":
  ts - This must be a pointer to character data. In Java and Ruby code 
       this must be an integer.

but have no idea of how to use it.

Any help or explanation please? Thanks a lot.

Iñaki Baz Castillo

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