Class: BinData::Struct

Inherits:
Base
  • Object
show all
Defined in:
lib/bindata/struct.rb

Overview

A Struct is an ordered collection of named data objects.

require 'bindata'

class Tuple < BinData::Record
  int8  :x
  int8  :y
  int8  :z
end

obj = BinData::Struct.new(:hide => :a,
                          :fields => [ [:int32le, :a],
                                       [:int16le, :b],
                                       [:tuple, :s] ])
obj.field_names   =># [:b, :s]

Parameters

Parameters may be provided at initialisation to control the behaviour of an object. These params are:

:fields

An array specifying the fields for this struct. Each element of the array is of the form [type, name, params]. Type is a symbol representing a registered type. Name is the name of this field. Params is an optional hash of parameters to pass to this field when instantiating it. If name is “” or nil, then that field is anonymous and behaves as a hidden field.

:hide

A list of the names of fields that are to be hidden from the outside world. Hidden fields don’t appear in #snapshot or #field_names but are still accessible by name.

:endian

Either :little or :big. This specifies the default endian of any numerics in this struct, or in any nested data objects.

:search_prefix

Allows abbreviated type names. If a type is unrecognised, then each prefix is applied until a match is found.

Field Parameters

Fields may have have extra parameters as listed below:

:onlyif

Used to indicate a data object is optional. if false, this object will not be included in any calls to #read, #write, #num_bytes or #snapshot.

:byte_align

This field’s rel_offset must be a multiple of :byte_align.

Direct Known Subclasses

Record

Defined Under Namespace

Classes: Snapshot

Constant Summary collapse

RESERVED =

These reserved words may not be used as field names

Hash[*
                 (Hash.instance_methods +
%w{alias and begin break case class def defined do else elsif
   end ensure false for if in module next nil not or redo
   rescue retry return self super then true undef unless until
   when while yield} +
%w{array element index value} ).collect { |name| name.to_sym }.
uniq.collect { |key| [key, true]

Instance Attribute Summary

Attributes inherited from Base

#parent

Instance Method Summary collapse

Methods inherited from Base

#==, #=~, #abs_offset, arg_processor, auto_call_delayed_io, bindata_name, #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

Methods included from RegisterNamePlugin

included

Methods included from Framework

#bit_aligned?

Instance Method Details

#[](key) ⇒ Object 



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# File 'lib/bindata/struct.rb', line 147

def [](key)
  find_obj_for_name(key)
end

#[]=(key, value) ⇒ Object 



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# File 'lib/bindata/struct.rb', line 151

def []=(key, value)
  obj = find_obj_for_name(key)
  if obj
    obj.assign(value)
  end
end

#assign(val) ⇒ Object 



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# File 'lib/bindata/struct.rb', line 95

def assign(val)
  clear
  assign_fields(val)
end

#clear ⇒ Object

:nodoc:



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# File 'lib/bindata/struct.rb', line 87

def clear #:nodoc:
  @field_objs.each { |f| f.clear unless f.nil? }
end

#clear? ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/bindata/struct.rb', line 91

def clear? #:nodoc:
  @field_objs.all? { |f| f.nil? or f.clear? }
end

#debug_name_of(child) ⇒ Object

:nodoc:



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# File 'lib/bindata/struct.rb', line 121

def debug_name_of(child) #:nodoc:
  field_name = @field_names[find_index_of(child)]
  "#{debug_name}.#{field_name}"
end

#do_num_bytes ⇒ Object

:nodoc:



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# File 'lib/bindata/struct.rb', line 142

def do_num_bytes #:nodoc:
  instantiate_all_objs
  sum_num_bytes_for_all_fields
end

#do_read(io) ⇒ Object

:nodoc:



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# File 'lib/bindata/struct.rb', line 132

def do_read(io) #:nodoc:
  instantiate_all_objs
  @field_objs.each { |f| f.do_read(io) if include_obj?(f) }
end

#do_write(io) ⇒ Object

:nodoc



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# File 'lib/bindata/struct.rb', line 137

def do_write(io) #:nodoc
  instantiate_all_objs
  @field_objs.each { |f| f.do_write(io) if include_obj?(f) }
end

#each_pair ⇒ Object 



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# File 'lib/bindata/struct.rb', line 162

def each_pair
  @field_names.compact.each do |name|
    yield [name, find_obj_for_name(name)]
  end
end

#field_names(include_hidden = false) ⇒ Object

Returns a list of the names of all fields accessible through this object. include_hidden specifies whether to include hidden names in the listing.



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# File 'lib/bindata/struct.rb', line 112

def field_names(include_hidden = false)
  if include_hidden
    @field_names.compact
  else
    hidden = get_parameter(:hide) || []
    @field_names.compact - hidden
  end
end

#has_key?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/bindata/struct.rb', line 158

def has_key?(key)
  @field_names.index(base_field_name(key))
end

#initialize_instance ⇒ Object 



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# File 'lib/bindata/struct.rb', line 83

def initialize_instance
  @field_objs  = []
end

#initialize_shared_instance ⇒ Object 



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# File 'lib/bindata/struct.rb', line 75

def initialize_shared_instance
  fields = get_parameter(:fields)
  @field_names = fields.field_names.freeze
  extend ByteAlignPlugin if fields.any_field_has_parameter?(:byte_align)
  define_field_accessors
  super
end

#offset_of(child) ⇒ Object

:nodoc:



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# File 'lib/bindata/struct.rb', line 126

def offset_of(child) #:nodoc:
  instantiate_all_objs
  sum = sum_num_bytes_below_index(find_index_of(child))
  child.bit_aligned? ? sum.floor : sum.ceil
end

#snapshot ⇒ Object 



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# File 'lib/bindata/struct.rb', line 100

def snapshot
  snapshot = Snapshot.new
  field_names.each do |name|
    obj = find_obj_for_name(name)
    snapshot[name] = obj.snapshot if include_obj?(obj)
  end
  snapshot
end