Class: BinData::Primitive

Inherits:
BasePrimitive show all
Extended by:
DSLMixin
Defined in:
lib/bindata/primitive.rb

Overview

A Primitive is a declarative way to define a new BinData data type. The data type must contain a primitive value only, i.e numbers or strings. For new data types that contain multiple values see BinData::Record.

To define a new data type, set fields as if for Record and add a #get and #set method to extract / convert the data between the fields and the #value of the object.

require 'bindata'

class PascalString < BinData::Primitive
  uint8  :len,  value: -> { data.length }
  string :data, read_length: :len

  def get
    self.data
  end

  def set(v)
    self.data = v
  end
end

ps = PascalString.new(initial_value: "hello")
ps.to_binary_s #=> "\005hello"
ps.read("\003abcde")
ps #=> "abc"

# Unsigned 24 bit big endian integer
class Uint24be < BinData::Primitive
  uint8 :byte1
  uint8 :byte2
  uint8 :byte3

  def get
    (self.byte1 << 16) | (self.byte2 << 8) | self.byte3
  end

  def set(v)
    v = 0 if v < 0
    v = 0xffffff if v > 0xffffff

    self.byte1 = (v >> 16) & 0xff
    self.byte2 = (v >>  8) & 0xff
    self.byte3 =  v        & 0xff
  end
end

u24 = Uint24be.new
u24.read("\x12\x34\x56")
"0x%x" % u24 #=> 0x123456

Parameters

Primitive objects accept all the parameters that BinData::BasePrimitive do.

Instance Attribute Summary

Attributes inherited from Base

#parent

Class Method Summary collapse

Instance Method Summary collapse

Methods included from DSLMixin

dsl_parser, to_ary, to_str

Methods inherited from BasePrimitive

#<=>, #clear?, #do_read, #do_read_with_hook, #eql?, #hash, #initialize_shared_instance, #snapshot, #trace_value, turn_off_tracing, turn_on_tracing, #value, #value=

Methods inherited from Base

#==, #=~, #abs_offset, arg_processor, auto_call_delayed_io, bindata_name, #clear, #debug_name, #eval_parameter, #get_parameter, #has_parameter?, #initialize_with_warning, #inspect, #lazy_evaluator, #new, #num_bytes, #pretty_print, #read, read, register_subclasses, #rel_offset, #safe_respond_to?, #to_binary_s, #to_hex, #to_s, unregister_self, #write

Methods included from AcceptedParametersPlugin

#accepted_parameters, #default_parameters, #mandatory_parameters, #mutually_exclusive_parameters, #optional_parameters

Methods included from CheckOrAdjustOffsetPlugin

included, #initialize_shared_instance

Methods included from RegisterNamePlugin

included, #initialize_shared_instance

Methods included from Framework

#bit_aligned?, #clear?, #offset_of, #snapshot

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(symbol, *args, &block) ⇒ Object

:nodoc:



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# File 'lib/bindata/primitive.rb', line 80

def method_missing(symbol, *args, &block) #:nodoc:
  if @struct.respond_to?(symbol)
    @struct.__send__(symbol, *args, &block)
  else
    super
  end
end

Class Method Details

.bit_aligned ⇒ Object 



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# File 'lib/bindata/alignment.rb', line 76

def Primitive.bit_aligned
  fail "'bit_aligned' is not needed for BinData::Primitives"
end

Instance Method Details

#assign(val) ⇒ Object 



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# File 'lib/bindata/primitive.rb', line 88

def assign(val)
  super(val)
  set(_value)
  @value = get
end

#debug_name_of(child) ⇒ Object

:nodoc:



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# File 'lib/bindata/primitive.rb', line 94

def debug_name_of(child) #:nodoc:
  debug_name + "-internal-"
end

#do_num_bytes ⇒ Object 



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# File 'lib/bindata/primitive.rb', line 103

def do_num_bytes
  set(_value)
  @struct.do_num_bytes
end

#do_write(io) ⇒ Object 



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# File 'lib/bindata/primitive.rb', line 98

def do_write(io)
  set(_value)
  @struct.do_write(io)
end

#initialize_instance ⇒ Object 



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# File 'lib/bindata/primitive.rb', line 71

def initialize_instance
  super
  @struct = BinData::Struct.new(get_parameter(:struct_params), self)
end

#respond_to?(symbol, include_private = false) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/bindata/primitive.rb', line 76

def respond_to?(symbol, include_private = false) #:nodoc:
  @struct.respond_to?(symbol, include_private) || super
end