From: Joel VanderWerf <vjoel@...>
Date: 2005-10-10T10:31:29+09:00
Subject: Re: [ANN] BitStruct

Someone asked offline about block-based initialization, and BitStruct
supports that, as well as hash-based and string-based. Here are the
variants:

  ip1 = IP.new
  ip1.ip_tos = 0
  ip1.ip_len = 0
  ip1.ip_id  = 0
  ip1.ip_off = 0
  ip1.ip_ttl = 255
  ip1.ip_p   = 255
  ip1.ip_sum = 0
  ip1.ip_src = "192.168.1.4"
  ip1.ip_dst = "192.168.1.255"
  ip1.body   = "This is the payload text."
  ip1.ip_len = ip1.length

  ip2 = IP.new do |ip|
    ip.ip_tos = 0
    ip.ip_len = 0
    ip.ip_id  = 0
    ip.ip_off = 0
    ip.ip_ttl = 255
    ip.ip_p   = 255
    ip.ip_sum = 0
    ip.ip_src = "192.168.1.4"
    ip.ip_dst = "192.168.1.255"
    ip.body   = "This is the payload text."
    ip.ip_len = ip.length
  end

  ip3 = IP.new(
    :ip_tos => 0,
    :ip_len => 0,
    :ip_id  => 0,
    :ip_off => 0,
    :ip_ttl => 255,
    :ip_p   => 255,
    :ip_sum => 0,
    :ip_src => "192.168.1.4",
    :ip_dst => "192.168.1.255",
    :body   => "This is the payload text."
  ) do |ip|
    ip.ip_len = ip.length
  end

  ip4 = IP.new(ip1) # Construct from a BitStruct (or String)

Btw, if you've ever wanted to write ping in ruby, check out ping-recv.rb
in the example dir.

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407