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#! /usr/bin/env ruby
require 'erb'
require 'optparse'
def v6rev(input)
# Parse the input to separate address and netmask
address, netmask = input.split('/')
netmask = netmask.to_i
# Calculate how many bits we actually have (128 - missing bits)
remaining_bits = 128 - netmask
remaining_groups = remaining_bits / 16
# Expand the partial address within the context of just the remaining bits
expanded_suffix = expand_ipv6_suffix(address, remaining_groups)
# Convert to hex string and get nibbles
hex_string = expanded_suffix.gsub(':', '')
# Split into individual nibbles and reverse for PTR format
nibbles = hex_string.chars.reverse
# Join with dots
nibbles.join('.')
end
def expand_ipv6_suffix(address, total_groups)
# Handle :: expansion within the context of just our suffix
if address.include?('::')
parts = address.split('::')
left_parts = parts[0].empty? ? [] : parts[0].split(':')
right_parts = parts[1].empty? ? [] : parts[1].split(':')
# Calculate how many zero groups we need
missing_groups = total_groups - left_parts.length - right_parts.length
zero_groups = ['0000'] * missing_groups
all_parts = left_parts + zero_groups + right_parts
else
all_parts = address.split(':')
end
# Pad each part to 4 digits
all_parts.map { |part| part.rjust(4, '0') }.join(':')
end
# Hash to store our -D variables
template_vars = {}
# Parse command line options
OptionParser.new do |opts|
opts.banner = "Usage: #{$0} [options] <input> <output>"
opts.on('-DVAR=VALUE', 'Define template variable') do |definition|
var, value = definition.split('=', 2)
if var && value
template_vars[var] = value
else
puts "Invalid -D format: #{definition}"
exit 1
end
end
opts.on('-h', '--help', 'Show this help') do
puts opts
exit
end
end.parse!
# Check we have the right number of remaining args
if ARGV.length != 2
puts "Usage: #{$0} [options] <input> <output>"
puts "Use -h for help"
exit 1
end
input_file = ARGV[0]
output_file = ARGV[1]
# Read the template
template = File.read(input_file)
# Create a binding with our variables
binding_context = binding
template_vars.each do |var, value|
binding_context.local_variable_set(var.to_sym, value)
end
# Process with ERB
erb = ERB.new(template, trim_mode: '-')
result = erb.result(binding_context)
# Write output
File.write(output_file, result)
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