class DBus::PacketMarshaller

D-Bus packet marshaller class

Class that handles the conversion (marshalling) of Ruby objects to (binary) payload data.

Attributes

endianness[R]

@return [:little,:big]

packet[R]

The current or result packet. FIXME: allow access only when marshalling is finished @return [String]

Public Class Methods

make_variant(value) click to toggle source

Make a [signature, value] pair for a variant

    # File lib/dbus/marshall.rb
346 def self.make_variant(value)
347   # TODO: mix in _make_variant to String, Integer...
348   if value == true
349     ["b", true]
350   elsif value == false
351     ["b", false]
352   elsif value.nil?
353     ["b", nil]
354   elsif value.is_a? Float
355     ["d", value]
356   elsif value.is_a? Symbol
357     ["s", value.to_s]
358   elsif value.is_a? Array
359     ["av", value.map { |i| make_variant(i) }]
360   elsif value.is_a? Hash
361     h = {}
362     value.each_key { |k| h[k] = make_variant(value[k]) }
363     key_type = if value.empty?
364                  "s"
365                else
366                  t, = make_variant(value.first.first)
367                  t
368                end
369     ["a{#{key_type}v}", h]
370   elsif value.respond_to? :to_str
371     ["s", value.to_str]
372   elsif value.respond_to? :to_int
373     i = value.to_int
374     if Data::Int32.range.cover?(i)
375       ["i", i]
376     elsif Data::Int64.range.cover?(i)
377       ["x", i]
378     else
379       ["t", i]
380     end
381   end
382 end

new(offset = 0, endianness: HOST_ENDIANNESS) click to toggle source

Create a new marshaller, setting the current packet to the empty packet.

    # File lib/dbus/marshall.rb
172 def initialize(offset = 0, endianness: HOST_ENDIANNESS)
173   @endianness = endianness
174   @packet = ""
175   @offset = offset # for correct alignment of nested marshallers
176 end

Public Instance Methods

align(alignment) click to toggle source

Align the buffer with NULL (0) bytes on a byte length of alignment.

    # File lib/dbus/marshall.rb
190 def align(alignment)
191   pad_count = num_align(@offset + @packet.bytesize, alignment) - @offset
192   @packet = @packet.ljust(pad_count, 0.chr)
193 end

append(type, val) click to toggle source

Append a value val to the packet based on its type.

Host native endianness is used, declared in Message#marshall

@param type [SingleCompleteType] (or Integer or {Type}) @param val [::Object]

    # File lib/dbus/marshall.rb
224 def append(type, val)
225   raise TypeException, "Cannot send nil" if val.nil?
226 
227   type = type.chr if type.is_a?(Integer)
228   type = Type::Parser.new(type).parse[0] if type.is_a?(String)
229   # type is [Type] now
230   data_class = Data::BY_TYPE_CODE[type.sigtype]
231   if data_class.nil?
232     raise NotImplementedError,
233           "sigtype: #{type.sigtype} (#{type.sigtype.chr})"
234   end
235 
236   if data_class.fixed?
237     align(data_class.alignment)
238     data = data_class.new(val)
239     @packet += data.marshall(endianness)
240   elsif data_class.basic?
241     val = val.value if val.is_a?(Data::Basic)
242     align(data_class.size_class.alignment)
243     size_data = data_class.size_class.new(val.bytesize)
244     @packet += size_data.marshall(endianness)
245     # Z* makes a binary string, as opposed to interpolation
246     @packet += [val].pack("Z*")
247   else
248     case type.sigtype
249 
250     when Type::VARIANT
251       append_variant(val)
252     when Type::ARRAY
253       val = val.exact_value if val.is_a?(Data::Array)
254       append_array(type.child, val)
255     when Type::STRUCT, Type::DICT_ENTRY
256       val = val.exact_value if val.is_a?(Data::Struct) || val.is_a?(Data::DictEntry)
257       unless val.is_a?(Array) || val.is_a?(Struct)
258         type_name = Type::TYPE_MAPPING[type.sigtype].first
259         raise TypeException, "#{type_name} expects an Array or Struct, seen #{val.class}"
260       end
261 
262       if type.sigtype == Type::DICT_ENTRY && val.size != 2
263         raise TypeException, "DICT_ENTRY expects a pair"
264       end
265 
266       if type.members.size != val.size
267         type_name = Type::TYPE_MAPPING[type.sigtype].first
268         raise TypeException, "#{type_name} has #{val.size} elements but type info for #{type.members.size}"
269       end
270 
271       struct do
272         type.members.zip(val).each do |t, v|
273           append(t, v)
274         end
275       end
276     else
277       raise NotImplementedError,
278             "sigtype: #{type.sigtype} (#{type.sigtype.chr})"
279     end
280   end
281 end

append_array(child_type, val) click to toggle source

@param child_type [Type]

    # File lib/dbus/marshall.rb
323 def append_array(child_type, val)
324   if val.is_a?(Hash)
325     raise TypeException, "Expected an Array but got a Hash" if child_type.sigtype != Type::DICT_ENTRY
326 
327     # Damn ruby rocks here
328     val = val.to_a
329   end
330   # If string is received and ay is expected, explode the string
331   if val.is_a?(String) && child_type.sigtype == Type::BYTE
332     val = val.bytes
333   end
334   if !val.is_a?(Enumerable)
335     raise TypeException, "Expected an Enumerable of #{child_type.inspect} but got a #{val.class}"
336   end
337 
338   array(child_type) do
339     val.each do |elem|
340       append(child_type, elem)
341     end
342   end
343 end

append_variant(val) click to toggle source

    # File lib/dbus/marshall.rb
283 def append_variant(val)
284   vartype = nil
285   if val.is_a?(DBus::Data::Variant)
286     vartype = val.member_type
287     vardata = val.exact_value
288   elsif val.is_a?(DBus::Data::Container)
289     vartype = val.type
290     vardata = val.exact_value
291   elsif val.is_a?(DBus::Data::Base)
292     vartype = val.type
293     vardata = val.value
294   elsif val.is_a?(Array) && val.size == 2
295     case val[0]
296     when Type
297       vartype, vardata = val
298     # Ambiguous but easy to use, because Type
299     # cannot construct "as" "a{sv}" easily
300     when String
301       begin
302         parsed = Type::Parser.new(val[0]).parse
303         vartype = parsed[0] if parsed.size == 1
304         vardata = val[1]
305       rescue Type::SignatureException
306         # no assignment
307       end
308     end
309   end
310   if vartype.nil?
311     vartype, vardata = PacketMarshaller.make_variant(val)
312     vartype = Type::Parser.new(vartype).parse[0]
313   end
314 
315   append(Data::Signature.type, vartype.to_s)
316   align(vartype.alignment)
317   sub = PacketMarshaller.new(@offset + @packet.bytesize, endianness: endianness)
318   sub.append(vartype, vardata)
319   @packet += sub.packet
320 end

array(type) { || ... } click to toggle source

Append the array type type to the packet and allow for appending the child elements.

    # File lib/dbus/marshall.rb
197 def array(type)
198   # Thanks to Peter Rullmann for this line
199   align(4)
200   sizeidx = @packet.bytesize
201   @packet += "ABCD"
202   align(type.alignment)
203   contentidx = @packet.bytesize
204   yield
205   sz = @packet.bytesize - contentidx
206   raise InvalidPacketException if sz > 67_108_864
207 
208   sz_data = Data::UInt32.new(sz)
209   @packet[sizeidx...sizeidx + 4] = sz_data.marshall(endianness)
210 end

num_align(num, alignment) click to toggle source

Round num up to the specified power of two, alignment

    # File lib/dbus/marshall.rb
179 def num_align(num, alignment)
180   case alignment
181   when 1, 2, 4, 8
182     bits = alignment - 1
183     (num + bits) & ~bits
184   else
185     raise ArgumentError, "Unsupported alignment #{alignment}"
186   end
187 end

struct() { || ... } click to toggle source

Align and allow for appending struct fields.

    # File lib/dbus/marshall.rb
213 def struct
214   align(8)
215   yield
216 end