class Resolv::DNS::Name

A representation of a DNS name.

Public Class Methods

create(arg) click to toggle source

Creates a new DNS name from arg. arg can be:

Name: returns arg.
String: Creates a new Name.

# File lib/resolv.rb, line 1269
def self.create(arg)
  case arg
  when Name
    return arg
  when String
    # A hostname is runtime data rather than a programming mistake, so
    # both size limits surface as ResolvError to stay rescuable alongside
    # the rest of name resolution. The type check below is a caller
    # mistake and keeps raising ArgumentError.
    begin
      labels = Label.split(arg)
    rescue ArgumentError => e
      raise ResolvError.new(e.message)
    end
    # Label::Str enforces the per-label limit. Only the total is knowable
    # here, and it counts the encoded form, so size starts at 1 for the
    # root label's terminating zero octet. [RFC 1035 2.3.4, 3.1]
    size = 1
    labels.each do |label|
      size += 1 + label.string.bytesize
      if size > 255
        raise ResolvError.new("DNS name is too long (#{size} octets, max 255): #{arg.inspect}")
      end
    end
    return Name.new(labels, /\.\z/ =~ arg ? true : false)
  else
    raise ArgumentError.new("cannot interpret as DNS name: #{arg.inspect}")
  end
end

Public Instance Methods

absolute?() click to toggle source

True if this name is absolute.

# File lib/resolv.rb, line 1319
def absolute?
  return @absolute
end

subdomain_of?(other) click to toggle source

Returns true if other is a subdomain.

Example:

domain = Resolv::DNS::Name.create("y.z")
p Resolv::DNS::Name.create("w.x.y.z").subdomain_of?(domain) #=> true
p Resolv::DNS::Name.create("x.y.z").subdomain_of?(domain) #=> true
p Resolv::DNS::Name.create("y.z").subdomain_of?(domain) #=> false
p Resolv::DNS::Name.create("z").subdomain_of?(domain) #=> false
p Resolv::DNS::Name.create("x.y.z.").subdomain_of?(domain) #=> false
p Resolv::DNS::Name.create("w.z").subdomain_of?(domain) #=> false

# File lib/resolv.rb, line 1345
def subdomain_of?(other)
  raise ArgumentError, "not a domain name: #{other.inspect}" unless Name === other
  return false if @absolute != other.absolute?
  other_len = other.length
  return false if @labels.length <= other_len
  return @labels[-other_len, other_len] == other.to_a
end

to_s() click to toggle source

returns the domain name as a string.

The domain name doesn’t have a trailing dot even if the name object is absolute.

Example:

p Resolv::DNS::Name.create("x.y.z.").to_s #=> "x.y.z"
p Resolv::DNS::Name.create("x.y.z").to_s #=> "x.y.z"

# File lib/resolv.rb, line 1380
def to_s
  return @labels.join('.')
end