Class: GPSTool::Message

Inherits:
Object
  • Object
show all
Defined in:
lib/gpstool/message.rb

Direct Known Subclasses

Devices::RBT2300::Message

Constant Summary collapse

@@messages = 
{}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(body) ⇒ Message 



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# File 'lib/gpstool/message.rb', line 86

def initialize(body)
  if Array === body
    @name = body.shift
    @parts = body
  else
    @name, @parts = body.split(",", 2)
  
    if @parts
      if structure == nil
        @parts = @parts.split(",")
      elsif structure.size > 1
        @parts = @parts.split(",", structure.size)
      else
        @parts = [@parts]
      end
    else
      @parts = []
    end
  end
end

Instance Attribute Details

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/gpstool/message.rb', line 108

def name
  @name
end

#parts ⇒ Object (readonly)

Returns the value of attribute parts.



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# File 'lib/gpstool/message.rb', line 107

def parts
  @parts
end

Class Method Details

.checksum(data) ⇒ Object 



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# File 'lib/gpstool/message.rb', line 25

def self.checksum(data)
  sum = 0
  
  data.size.times do |i|
    sum = sum ^ data[i]
  end
  
  return sum
end

.checksum_hex(body) ⇒ Object 



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# File 'lib/gpstool/message.rb', line 35

def self.checksum_hex(body)
  sprintf("%X", checksum(body).to_i).rjust(2, "0")
end

.parse(data) ⇒ Object 



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# File 'lib/gpstool/message.rb', line 58

def self.parse(data)
  data = self.validate(data)
  
  return self.new(data)
end

.read(io, options = {}) ⇒ Object 



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# File 'lib/gpstool/message.rb', line 68

def self.read(io, options = {})
  # Try to synchronise to the start message boundary
  while io.readbytes(1) != '$'
  end

  name = ''
  while true
    c = io.readbytes(1)
    
    if c == ',' || c == '*'
      io.ungetc(c[0])
      return self.read_body(io, name, options)
    end

    name += c
  end
end

.read_body(io, name, options) ⇒ Object 



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# File 'lib/gpstool/message.rb', line 64

def self.read_body(io, name, options)
  return self.parse('$' + name + io.gets)
end

.validate(data) ⇒ Object

This function performs validation and normalisation on the input data.



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# File 'lib/gpstool/message.rb', line 40

def self.validate(data)
  data.strip!
  
  data = data[1..-1] if data[0,1] == "$"
  sum = nil
  
  if data[-3,1] == "*"
    sum = data[-2,2]
    data = data[0..-4]
    
    if checksum_hex(data) != sum
      raise InvalidChecksumError.new(data, sum)
    end
  end
  
  return data
end

Instance Method Details

#[](key) ⇒ Object 



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# File 'lib/gpstool/message.rb', line 122

def [](key)
  if structure
    offset = structure.index(key)
    return @parts[offset]
  end

  return nil
end

#structure ⇒ Object 



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# File 'lib/gpstool/message.rb', line 110

def structure
  messages = self.class.class_eval('@@messages')
  messages[@name]
end

#to_hash ⇒ Object 



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# File 'lib/gpstool/message.rb', line 115

def to_hash
  result = {}
  structure.each_with_index do |n,i|
    result[n] = @parts[i] if n
  end
end

#to_s ⇒ Object 



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# File 'lib/gpstool/message.rb', line 131

def to_s
  body = nil
  
  if @parts.length > 0
    body = "#{@name},#{@parts.join(',')}"
  else
    body = @name
  end
  
  sum = self.class.checksum_hex(body)
  
  return "$#{body}*#{sum}"
end