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require 'bindata/base'
require 'bindata/dsl'
module BinData
# A Section is a layer on top of a stream that transforms the underlying
# data. This allows BinData to process a stream that has multiple
# encodings. e.g. Some data data is compressed or encrypted.
#
# require 'bindata'
#
# class XorTransform < BinData::IO::Transform
# def initialize(xor)
# super()
# @xor = xor
# end
#
# def read(n)
# chain_read(n).bytes.map { |byte| (byte ^ @xor).chr }.join
# end
#
# def write(data)
# chain_write(data.bytes.map { |byte| (byte ^ @xor).chr }.join)
# end
# end
#
# obj = BinData::Section.new(transform: -> { XorTransform.new(0xff) },
# type: [:string, read_length: 5])
#
# obj.read("\x97\x9A\x93\x93\x90") #=> "hello"
#
#
# == Parameters
#
# Parameters may be provided at initialisation to control the behaviour of
# an object. These params are:
#
# <tt>:transform</tt>:: A callable that returns a new BinData::IO::Transform.
# <tt>:type</tt>:: The single type inside the buffer. Use a struct if
# multiple fields are required.
class Section < BinData::Base
extend DSLMixin
dsl_parser :section
arg_processor :section
mandatory_parameters :transform, :type
def initialize_instance
@type = get_parameter(:type).instantiate(nil, self)
end
def clear?
@type.clear?
end
def assign(val)
@type.assign(val)
end
def snapshot
@type.snapshot
end
def respond_to_missing?(symbol, include_all = false) # :nodoc:
@type.respond_to?(symbol, include_all) || super
end
def method_missing(symbol, *args, &block) # :nodoc:
@type.__send__(symbol, *args, &block)
end
def do_read(io) # :nodoc:
io.transform(eval_parameter(:transform)) do |transformed_io, _raw_io|
@type.do_read(transformed_io)
end
end
def do_write(io) # :nodoc:
io.transform(eval_parameter(:transform)) do |transformed_io, _raw_io|
@type.do_write(transformed_io)
end
end
def do_num_bytes # :nodoc:
to_binary_s.size
end
end
class SectionArgProcessor < BaseArgProcessor
include MultiFieldArgSeparator
def sanitize_parameters!(obj_class, params)
params.merge!(obj_class.dsl_params)
params.sanitize_object_prototype(:type)
end
end
end
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