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A thread-safe class supporting concurrent reads and writes
# tested on Crystal 0.31.1
class WeatherStation
alias StationState = Hash(Int32, Float64)
private record SetTemperature, id : Int32, temperature : Float64
private record GetTemperatures, return_channel : Channel(StationState)
@requests = Channel(SetTemperature | GetTemperatures).new
def initialize
@current_temperatures = StationState.new
spawn(name: "weather_station") do
loop do
case command = @requests.receive
when SetTemperature
@current_temperatures[command.id] = command.temperature
when GetTemperatures
command.return_channel.send @current_temperatures
end
end
end
end
def set_temp(sensor_id : Int32, temperature : Float64)
@requests.send SetTemperature.new(sensor_id, temperature)
end
def get_temps : StationState
Channel(StationState).new.tap { |return_channel|
@requests.send GetTemperatures.new(return_channel)
}.receive
end
end
station = WeatherStation.new
Sensors = 6
Operators = 3
# simulate sensors
Sensors.times { |i|
spawn(name: "sensor_#{i}") do
loop do
temperature = rand
station.set_temp(i, temperature)
puts "s_#{i}: sent #{temperature}"
sleep rand
end
end
}
# simulate operators
Operators.times { |i|
spawn(name: "operator_#{i}") do
loop do
temperatures = station.get_temps
puts "o_#{i}: received #{temperatures}"
sleep 2 * rand
end
end
}
sleep # suspend Main fiber
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