Class: Fiddle::CStructEntity

Inherits:
Pointer show all
Includes:
PackInfo, ValueUtil
Defined in:
ext/fiddle/lib/fiddle/struct.rb

Overview

A pointer to a C structure

Direct Known Subclasses

CUnionEntity

Constant Summary

Constants included from PackInfo

PackInfo::ALIGN_MAP, PackInfo::PACK_MAP, PackInfo::SIZE_MAP

Class Method Summary collapse

Instance Method Summary collapse

Methods included from ValueUtil

#signed_value, #unsigned_value, #wrap_arg, #wrap_args

Methods included from PackInfo

align

Methods inherited from Pointer

#+, #+@, #-, #-@, #<=>, #==, [], #call_free, #eql?, #free, #free=, #freed?, #inspect, #null?, #ptr, read, #ref, #size, #size=, #to_i, #to_int, to_ptr, #to_str, #to_value, write

Constructor Details

#initialize(addr, types, func = nil) ⇒ CStructEntity

Wraps the C pointer addr as a C struct with the given types.

When the instance is garbage collected, the C function func is called.

See also Fiddle::Pointer.new



340
341
342
343
344
345
346
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 340

def initialize(addr, types, func = nil)
  if func && addr.is_a?(Pointer) && addr.free
    raise ArgumentError, 'free function specified on both underlying struct Pointer and when creating a CStructEntity - who do you want to free this?'
  end
  set_ctypes(types)
  super(addr, @size, func)
end

Class Method Details

.alignment(types) ⇒ Object 



277
278
279
280
281
282
283
284
285
286
287
288
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 277

def CStructEntity.alignment(types)
  max = 1
  types.each do |type, count = 1|
    if type.respond_to?(:entity_class)
      n = type.alignment
    else
      n = ALIGN_MAP[type]
    end
    max = n if n > max
  end
  max
end

.malloc(types, func = nil, size = size(types), &block) ⇒ Object

Allocates a C struct with the types provided.

See Fiddle::Pointer.malloc for memory management issues.



293
294
295
296
297
298
299
300
301
302
303
304
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 293

def CStructEntity.malloc(types, func = nil, size = size(types), &block)
  if block_given?
    super(size, func) do |struct|
      struct.set_ctypes types
      yield struct
    end
  else
    struct = super(size, func)
    struct.set_ctypes types
    struct
  end
end

.size(types) ⇒ Object

Returns the offset for the packed sizes for the given types.

Fiddle::CStructEntity.size(
  [ Fiddle::TYPE_DOUBLE,
    Fiddle::TYPE_INT,
    Fiddle::TYPE_CHAR,
    Fiddle::TYPE_VOIDP ]) #=> 24



313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 313

def CStructEntity.size(types)
  offset = 0

  max_align = types.map { |type, count = 1|
    last_offset = offset

    if type.respond_to?(:entity_class)
      align = type.alignment
      type_size = type.size
    else
      align = PackInfo::ALIGN_MAP[type]
      type_size = PackInfo::SIZE_MAP[type]
    end
    offset = PackInfo.align(last_offset, align) +
             (type_size * count)

    align
  }.max

  PackInfo.align(offset, max_align)
end

Instance Method Details

#[](*args) ⇒ Object

Fetch struct member name if only one argument is specified. If two arguments are specified, the first is an offset and the second is a length and this method returns the string of length bytes beginning at offset.

Examples:

my_struct = struct(['int id']).malloc
my_struct.id = 1
my_struct['id'] # => 1
my_struct[0, 4] # => "\x01\x00\x00\x00".b



413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 413

def [](*args)
  return super(*args) if args.size > 1
  name = args[0]
  idx = @members.index(name)
  if( idx.nil? )
    raise(ArgumentError, "no such member: #{name}")
  end
  ty = @ctypes[idx]
  if( ty.is_a?(Array) )
    if ty.first.respond_to?(:entity_class)
      return @nested_structs[name]
    else
      r = super(@offset[idx], SIZE_MAP[ty[0]] * ty[1])
    end
  elsif ty.respond_to?(:entity_class)
    return @nested_structs[name]
  else
    r = super(@offset[idx], SIZE_MAP[ty.abs])
  end
  packer = Packer.new([ty])
  val = packer.unpack([r])
  case ty
  when Array
    case ty[0]
    when TYPE_VOIDP
      val = val.collect{|v| Pointer.new(v)}
    end
  when TYPE_VOIDP
    val = Pointer.new(val[0])
  else
    val = val[0]
  end
  if( ty.is_a?(Integer) && (ty < 0) )
    return unsigned_value(val, ty)
  elsif( ty.is_a?(Array) && (ty[0] < 0) )
    return StructArray.new(self + @offset[idx], ty[0], val)
  else
    return val
  end
end

#[]=(*args) ⇒ Object

Set struct member name, to value val. If more arguments are specified, writes the string of bytes to the memory at the given offset and length.

Examples:

my_struct = struct(['int id']).malloc
my_struct['id'] = 1
my_struct[0, 4] = "\x01\x00\x00\x00".b
my_struct.id # => 1



465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 465

def []=(*args)
  return super(*args) if args.size > 2
  name, val = *args
  name = name.to_s if name.is_a?(Symbol)
  nested_struct = @nested_structs[name]
  if nested_struct
    if nested_struct.is_a?(StructArray)
      if val.nil?
        nested_struct.each do |s|
          s.replace(nil)
        end
      else
        val.each_with_index do |v, i|
          nested_struct[i] = v
        end
      end
    else
      nested_struct.replace(val)
    end
    return val
  end
  idx = @members.index(name)
  if( idx.nil? )
    raise(ArgumentError, "no such member: #{name}")
  end
  ty  = @ctypes[idx]
  packer = Packer.new([ty])
  val = wrap_arg(val, ty, [])
  buff = packer.pack([val].flatten())
  super(@offset[idx], buff.size, buff)
  if( ty.is_a?(Integer) && (ty < 0) )
    return unsigned_value(val, ty)
  elsif( ty.is_a?(Array) && (ty[0] < 0) )
    return val.collect{|v| unsigned_value(v,ty[0])}
  else
    return val
  end
end

#assign_names(members) ⇒ Object

Set the names of the members in this C struct



349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 349

def assign_names(members)
  @members = []
  @nested_structs = {}
  members.each_with_index do |member, index|
    if member.is_a?(Array) # nested struct
      member_name = member[0]
      struct_type, struct_count = @ctypes[index]
      if struct_count.nil?
        struct = struct_type.new(to_i + @offset[index])
      else
        structs = struct_count.times.map do |i|
          struct_type.new(to_i + @offset[index] + i * struct_type.size)
        end
        struct = StructArray.new(to_i + @offset[index],
                                 struct_type,
                                 structs)
      end
      @nested_structs[member_name] = struct
    else
      member_name = member
    end
    @members << member_name
  end
end

#set_ctypes(types) ⇒ Object

Calculates the offsets and sizes for the given types in the struct.



375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 375

def set_ctypes(types)
  @ctypes = types
  @offset = []
  offset = 0

  max_align = types.map { |type, count = 1|
    orig_offset = offset
    if type.respond_to?(:entity_class)
      align = type.alignment
      type_size = type.size
    else
      align = ALIGN_MAP[type]
      type_size = SIZE_MAP[type]
    end
    offset = PackInfo.align(orig_offset, align)

    @offset << offset

    offset += (type_size * count)

    align
  }.max

  @size = PackInfo.align(offset, max_align)
end

#to_s ⇒ Object

:nodoc:



505
506
507
 
# File 'ext/fiddle/lib/fiddle/struct.rb', line 505

def to_s() # :nodoc:
  super(@size)
end