Class: Snap7::Variable

Inherits:
Object
  • Object
show all
Defined in:
lib/ffi-snap7/data_structures/variable.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(ident, address, type) ⇒ Variable

Returns a new instance of Variable.



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 8

def initialize(ident, address, type)
  addr_parts = address.scan(/\d+/)

  if address =~ /^DBX/
    fail "Invalid bit address '#{address}'" unless addr_parts.size == 2
  end

  @ident   = ident
  @address = address
  @byte    = addr_parts.first.to_i
  @bit     = addr_parts.last.to_i if addr_parts.size == 2
  @type    = type
end

Instance Attribute Details

#bit ⇒ Object (readonly)

Returns the value of attribute bit.



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 4

def bit
  @bit
end

#byte ⇒ Object (readonly)

Returns the value of attribute byte.



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 4

def byte
  @byte
end

#db ⇒ Object

Returns the value of attribute db.



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 5

def db
  @db
end

#ident ⇒ Object (readonly)

Returns the value of attribute ident.



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 4

def ident
  @ident
end

#type ⇒ Object (readonly)

Returns the value of attribute type.



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 4

def type
  @type
end

Instance Method Details

#address ⇒ Object 



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 44

def address
  ["DB#{db.number}", @address].compact.join('.')
end

#bit_size ⇒ Object 



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 23

def bit_size
  case @address
  when /^DBD/ # double (32 bit)
    32
  when /^DBW/ # word   (16 bit)
    16
  when /^DBB/ # byte   (8 bit)
    8
  when /^DBX/ # bit    (1 bit)
    1
  else
    fail "Invalid address '#{@address}' of variable #{@ident}. Cannot determine size."
  end
end

#byte_size ⇒ Object 



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 39

def byte_size
  @byte_size ||= (bit_size / 8.0).ceil
end

#decode(data) ⇒ Object 



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 49

def decode(data)
  var_data = data[byte, byte_size]

  case @type
  when :bool
    var_data.first[@bit] > 0

  when :int8
    var_data.pack('C1').unpack('c').first

  when :uint8
    var_data.pack('C1').unpack('C').first

  when :int16
    var_data.reverse.pack('C2').unpack('s').first

  when :uint16
    var_data.reverse.pack('C2').unpack('S').first

  when :int32
    var_data.reverse.pack('C4').unpack('l').first

  when :uint32
    var_data.reverse.pack('C4').unpack('L').first

  when :float32
    var_data.reverse.pack('C4').unpack('f').first

  else
    fail "Invalid type '#{@type}' of variable #{@ident}. Cannot decode data."
  end
end

#encode(value) ⇒ Object 



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# File 'lib/ffi-snap7/data_structures/variable.rb', line 83

def encode(value)
  case @type
  when :int8, :uint8
    [value]

  when :int16, :uint16
    [value].pack('s').unpack('C2').reverse

  when :int32, :uint32
    [value].pack('l').unpack('C4').reverse

  when :float32
    [value].pack('f').unpack('C4').reverse

  else
    fail "Invalid type '#{@type}' of variable #{@ident}. Cannot encode data."
  end
end