init, changed a few things for GEIGERnet-Server, added sounds for receiving RDS message

helpers.lua

@@ -0,0 +1,43 @@
+function ham_radio.validate_frequency(frequency, is_receiver)
+  if frequency == "" then
+    return { result = true, message = '' } -- empty frequency is allowed to disable transmitter/receiver
+  end
+  local transmission_is_allowed = true
+  local num_freq = tonumber(frequency)
+  local freq = tostring(num_freq)
+  if is_receiver == nil and next(ham_radio.find_transmitters(frequency)) then
+    if num_freq >= ham_radio.settings.locked_frequency.min
+    and num_freq <= ham_radio.settings.locked_frequency.max then
+      -- transmitter is in locked frequency range
+      transmission_is_allowed = false
+    end
+  end
+  local result = true
+  local message = ''
+  if freq ~= frequency or num_freq ~= math.floor(num_freq) then
+    result = false
+    message = 'Error: invalid frequency value.'
+  elseif num_freq == nil then
+    result = false
+    message = 'Error: frequency should be numeric.'
+  elseif num_freq < ham_radio.settings.frequency.min or num_freq > ham_radio.settings.frequency.max then
+    result = false
+    message = 'Error: frequency is out of range.'
+  elseif transmission_is_allowed == false then
+    result = false
+    message = 'Error: frequency is occupied by other transmitter.'
+  end
+  return { result = result, message = message }
+end
+
+function ham_radio.find_free_frequency(range)
+  local frequency = -1
+  while frequency == -1 do
+    frequency = tostring(math.floor(math.random(range.min, range.max)));
+    local are_there_transmitters = ham_radio.find_transmitters(frequency)
+    if next(are_there_transmitters) then
+      frequency = -1
+    end
+  end
+  return frequency
+end