Class: FFI::StructEx

Inherits:
Struct
  • Object
show all
Defined in:
lib/ffi/struct_ex/struct_ex.rb

Defined Under Namespace

Classes: BitLayout

Class Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ StructEx

Returns a new instance of StructEx.



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 93

def initialize(options = {})
  if options.is_a?(FFI::Pointer)
    super(options)
  else
    super()
    write(options)
  end
end

Class Attribute Details

.bit_layouts ⇒ Object (readonly)

Returns the value of attribute bit_layouts.



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 51

def bit_layouts
  @bit_layouts
end

.bits_size ⇒ Object (readonly)

Returns the value of attribute bits_size.



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 51

def bits_size
  @bits_size
end

Class Method Details

.alignment ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 86

def alignment
  return super unless self.bit_layouts
  #FIXME consider 24 bits situation
  FFI.find_type("uint#{bytes_size * 8}".to_sym).alignment
end

.bit_fields(*descs) ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 19

def bit_fields(*descs)
  struct_class = Class.new(StructEx) do
    layout(*descs)
  end

  bit_fields_class = Class.new(FFI::StructLayout::Field) do
    def initialize(name, offset, type)
      #TODO use a different native_type to avoid dummy field for struct
      super(name, offset, FFI::Type::Struct.new(self.class.struct_class))
    end

    def get(ptr)
      #self.class.struct_class == type.struct_class
      self.class.struct_class.new(ptr.slice(self.offset, self.size))
    end

    def put(ptr, value)
      self.class.struct_class.new(ptr.slice(self.offset, self.size)).write(value)
    end

    class << self
      attr_accessor :struct_class

      def alignment
        struct_class.alignment
      end
    end

    self.struct_class = struct_class
  end
end

.bytes_size ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 82

def bytes_size
  (bits_size + 7) >> 3
end

.layout(*descs) ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 53

def layout(*descs)
  if descs.size == 0 || !descs[1].is_a?(Integer)
    super(*descs)
    #@bits_size = self.size * 8
  else
    @bit_layouts = {}

    index = @bits_size = 0

    while index < descs.size
      bit_field_name, bits, texts = descs[index, 3]

      if texts.kind_of?(Hash)
        @bit_layouts[bit_field_name] = BitLayout.new(bit_field_name, bits, @bits_size, texts)
        index += 3
      else
        @bit_layouts[bit_field_name] = BitLayout.new(bit_field_name, bits, @bits_size)
        index += 2
      end

      @bits_size += bits
    end

    #FIXME consider 24 bits situation or larger than 32 bits
    #FIXME remove dummy field or have a better name for this field
    super(:dummy, "uint#{bytes_size * 8}".to_sym)
  end
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 141

def ==(other)
  if other.is_a?(Integer)
    self.read == other
  elsif other.is_a?(Hash)
    other.all? {|k, v| self[k] == self.look_for_value(k, v)}
  else
    super
  end
end

#[](bit_field_name) ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 102

def [](bit_field_name)
  return super unless self.class.bit_layouts && self.class.bit_layouts.keys.include?(bit_field_name)

  bit_layout = self.class.bit_layouts[bit_field_name]
  mask = ((1 << bit_layout.bits) - 1) << bit_layout.offset

  (self.read & mask) >> bit_layout.offset
end

#[]=(bit_field_name, value) ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 111

def []=(bit_field_name, value)
  return super unless self.class.bit_layouts && self.class.bit_layouts.keys.include?(bit_field_name)

  value = look_for_value(bit_field_name, value)

  bit_layout = self.class.bit_layouts[bit_field_name]
  mask = ((1 << bit_layout.bits) - 1) << bit_layout.offset

  self.write((self.read & (-1 - mask)) | ((value << bit_layout.offset) & mask))
end

#look_for_value(bit_field_name, value) ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 151

def look_for_value(bit_field_name, value)
  #FIXME add error handling
  if value.kind_of?(Integer)
    value
  elsif value.kind_of?(String)
    #FIXME this requires texts hash to have downcase key
    value = value.downcase
    if self.class.bit_layouts[bit_field_name].texts && self.class.bit_layouts[bit_field_name].texts[value]
      self.class.bit_layouts[bit_field_name].texts[value]
    else
      case value
        when /^\d+$/
          value.to_i
        when /^0x[\da-fA-F]+$/
          value.to_i(16)
        when /^0b[01]+$/
          value.to_i(2)
      end
    end
  else
    value
  end
end

#read ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 132

def read
  bytes = to_ptr.read_array_of_uint8(self.class.bytes_size)
  bytes.reverse.inject(0) {|value, n| (value << 8) | n}
end

#size ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 137

def size
  self.class.bytes_size
end

#write(value) ⇒ Object 



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# File 'lib/ffi/struct_ex/struct_ex.rb', line 122

def write(value)
  if value.is_a?(Integer)
    to_ptr.write_array_of_uint8(value.to_bytes(self.class.bytes_size))
  elsif value.is_a?(Hash)
    value.each do |bit_field_name, v|
      self[bit_field_name] = v if self.class.bit_layouts.keys.include? bit_field_name
    end
  end
end