km-psych

= Psych

• http://github.com/tenderlove/psych

== Description

Psych is a YAML parser and emitter. Psych leverages libyaml[http://libyaml.org] for it's YAML parsing and emitting capabilities. In addition to wrapping libyaml, Psych also knows how to serialize and de-serialize most Ruby objects to and from the YAML format.

== Install

You need Ruby 1.9.2-p0 or higher. Also install libyaml fx in one of the following ways...

$ brew install libyaml $ port install libyaml +universal $ yum install libyaml-devel

== Examples

Load YAML in to a Ruby object

Psych.load('--- foo') # => 'foo'

Emit YAML from a Ruby object

Psych.dump("foo") # => "--- foo\n...\n"

== Documentation

http://tenderlovemaking.com/2010/04/17/event-based-json-and-yaml-parsing/

Our event listener is only going to listen for scalar events, meaning that when Psych parses a string, it will send that string to our listener. There are many different events that can happen, so Psych ships with a handler from which you can inherit. If you check out the source for the base class handler, you can see what types of events your handler can intercept.

require 'psych'

class Listener < Psych::Handler def scalar(value, anchor, tag, plain, quoted, style) puts value end end

listener = Listener.new parser = Psych::Parser.new listener parser.parse DATA

END {"foo":"bar"}

In this example, our handler simply prints out every scalar value encountered. We created a new instance of the listener, pass that listener to a new instance of the parser, and tell the parser to parse DATA. We can hand the parser an IO object or a String object. This is important because we’d like to hand the parser our socket connection, that way the parser can deal with reading from the socket for us.

require 'socket' require 'psych'

class StreamClient def initialize user, pass @ba = ["#{user}:#{pass}"].pack('m').chomp end

def listen listener
  socket = TCPSocket.new 'stream.twitter.com', 80
  # .. (authentication) ...

  # Read the headers
  while((line = socket.readline) != "\r\n"); puts line if $DEBUG; end

  reader, writer = IO.pipe
  producer = Thread.new(socket, writer) do |s, io|
    loop do
      io.write "---\n"
      io.write s.read s.readline.strip.to_i 16
      io.write "...\n"
      s.read 2 # strip the blank line
    end
  end

  parser = Psych::Parser.new listener
  parser.parse reader

  producer.join
end

end

class Listener < Psych::Handler def initialize @was_text = false end

def scalar value, anchor, tag, plain, quoted, style
  puts value if @was_text
  @was_text = value == 'text'
end

end

StreamClient.new(ARGV[0], ARGV[1]).listen Listener.new

We configure the “listen” method in our client to munge the feed to a pipe, and hand that off to our YAML processor. I only care about the text of people’s tweets, so let’s modify our listener too.

== Dependencies

• libyaml

== Installation

• sudo port install libyaml +universal
• sudo gem install psych

== License

Copyright 2009 Aaron Patterson, et al.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.