Module: Dommy::Internal::Ipv4Parser

Defined in:
lib/dommy/internal/ipv4_parser.rb

Overview

WHATWG URL §host-parsing IPv4 number form. Accepts the four historical input shapes used by HTTP URLs:

a.b.c.d  (standard dotted-quad)
a.b.c    (last segment is 16 bits)
a.b      (last segment is 24 bits)
a        (32-bit single number)

Each numeric segment may be expressed in decimal, hex (‘0x` prefix), or octal (leading `0`). Output is always canonical dotted-decimal.

‘parse(host)` returns the canonical form, or `nil` if `host` doesn’t look like an IPv4 number form at all.

Class Method Summary collapse

Class Method Details

.parse(host) ⇒ Object 



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# File 'lib/dommy/internal/ipv4_parser.rb', line 20

def self.parse(host)
  return nil if host.nil? || host.empty?

  parts = host.split(".", -1)
  # WHATWG allows a single trailing empty (`1.2.3.4.`).
  parts = parts[0..-2] if parts.last == "" && parts.length > 1
  return nil if parts.empty? || parts.length > 4
  return nil if parts.any?(&:empty?)

  numbers = parts.map { |p| parse_number(p) }
  return nil if numbers.any?(&:nil?)

  # Recombine per the segment count rules.
  case numbers.length
  when 1
    n = numbers[0]
  when 2
    return nil if numbers[0] >= 256 || numbers[1] >= (1 << 24)

    n = numbers[0] * (1 << 24) + numbers[1]
  when 3
    if numbers[0] >= 256 ||
        numbers[1] >= 256 ||
        numbers[2] >= (1 << 16)
      return nil
    end

    n = numbers[0] * (1 << 24) + numbers[1] * (1 << 16) + numbers[2]
  when 4
    return nil if numbers.any? { |x| x >= 256 }

    n = numbers[0] *
      (1 << 24) +
      numbers[1] *
      (1 << 16) +
      numbers[2] *
      (1 << 8) +
      numbers[3]
  end

  return nil if n >= (1 << 32)

  [(n >> 24) & 0xFF, (n >> 16) & 0xFF, (n >> 8) & 0xFF, n & 0xFF].join(".")
end

.parse_number(str) ⇒ Object 



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# File 'lib/dommy/internal/ipv4_parser.rb', line 65

def self.parse_number(str)
  return nil if str.empty?

  radix = 10
  digits = str
  if str.length >= 2 && (str[0, 2] == "0x" || str[0, 2] == "0X")
    radix = 16
    digits = str[2..]
  elsif str.length >= 2 && str[0] == "0"
    radix = 8
    digits = str[1..]
  end

  # A bare radix prefix (`0x`, `0`) denotes the number 0.
  return 0 if digits.empty?

  valid =
    case radix
    when 16 then digits.match?(/\A[0-9a-fA-F]+\z/)
    when 8 then digits.match?(/\A[0-7]+\z/)
    else digits.match?(/\A[0-9]+\z/)
    end
  return nil unless valid

  digits.to_i(radix)
end