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

Returns a new instance of 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