Simple I2C Linux library for Ruby

i2cdev.rb

=begin

Copyright 2018 Javier Valencia

Redistribution and use in source and binary forms, with or without
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   this list of conditions and the following disclaimer.

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   this list of conditions and the following disclaimer in the documentation 
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   may be used to endorse or promote products derived from this software 
   without specific prior written permission.

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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
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=end

class I2CDev
	IOCTL_I2C_SLAVE = 0x0703
	
	def self.base_address # virtual method
		raise NoMethodError, "implement this class method in your subclass."
	end
	
	def initialize(i2c_bus_file, i2c_dev_addr = self.class.base_address)
		@i2c_bus_file = i2c_bus_file
		@i2c_dev_addr = i2c_dev_addr
	end
	
	def i2c_read(address, count)
		File.open(@i2c_bus_file, "r+") do |f|
			f.flock(File::LOCK_EX)
			f.ioctl(IOCTL_I2C_SLAVE, @i2c_dev_addr)
			
			f.syswrite([address].pack("C"))
			str = f.sysread(count)
			
			count == 1 ? str.bytes[0] : str.bytes
		end
	end
	
	def i2c_write(address, content)
		File.open(@i2c_bus_file, "r+") do |f|
			f.flock(File::LOCK_EX)
			f.ioctl(IOCTL_I2C_SLAVE, @i2c_dev_addr)
			
			case content
				when String
					f.syswrite([address].pack("C") + content)
				when Array # of bytes, truncated
					f.syswrite([address].pack("C") + content.pack("C*"))
				when Fixnum # single byte, truncated
					f.syswrite([address].pack("C") + content.chr)
				else
					raise TypeError, "data type <#{content.class}> not supported."
			end
		end
	end
end