class Fiddle::CStructEntity

Parent:: Fiddle::Pointer

A pointer to a C structure

Public Class Methods

alignment(types) Show source

# File ext/fiddle/lib/fiddle/struct.rb, line 206
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)) { |struct| ... } Show source

# File ext/fiddle/lib/fiddle/struct.rb, line 222
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

Allocates a C struct with the types provided.

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

Calls superclass method Fiddle::Pointer::malloc

new(addr, types, func = nil) Show source

# File ext/fiddle/lib/fiddle/struct.rb, line 269
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

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.

Public Instance Methods

[](*args) Show source

# File ext/fiddle/lib/fiddle/struct.rb, line 342
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

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

Calls superclass method Fiddle::Pointer::[]

[]=(*args) Show source

# File ext/fiddle/lib/fiddle/struct.rb, line 394
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

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

Calls superclass method Fiddle::Pointer#[]=

assign_names(members) Show source

# File ext/fiddle/lib/fiddle/struct.rb, line 278
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 the names of the members in this C struct

set_ctypes(types) Show source

# File ext/fiddle/lib/fiddle/struct.rb, line 304
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

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

Ruby Core © 1993–2020 Yukihiro Matsumoto
Licensed under the Ruby License.
Ruby Standard Library © contributors
Licensed under their own licenses.