SharedVar.lua

SharedVar.lua

require 'adrodoc55.wol.EventQueue'

local requestEventName = 'SharedVarRequest-'
local updateEventName = 'SharedVarUpdate-'

declare('SharedVar')

local function createSharedVar(name)
  Check.isString(name, 1)
  local result = {
    name = name,
    requestQueue = Events.connect(requestEventName..name),
    updateQueue = Events.connect(updateEventName..name)
  }
  setmetatable(result, SharedVar)
  return result
end

function SharedVar.new(name, value)
  local result = createSharedVar(name)
  result:fireUpdate(value)
  return result
end
Help.on(SharedVar.new) [[Creates a new SharedVar with the specified name and value. A
SharedVar is used to share memory between multiple spells.
SharedVars with the same name always contain the same value,
even across different spells. Note that modifying the content
of a shared table does not update the content for other
SharedVars.
This constructor updates the shared value regardless of a
potential previous value. If you don't want to override the
shared value use 'SharedVar.connect()' instead.

Parameters:
  - name: the public name for the new SharedVar
  - value: the new shared value (defaults to nil)
]]

function SharedVar.connect(name)
  local result = createSharedVar(name)
  result.connecting = true
  Events.fire(requestEventName..name)
  return result
end
Help.on(SharedVar.connect) [[Creates a new SharedVar with the specified name and value. A
SharedVar is used to share memory between multiple spells.
SharedVars with the same name always contain the same value,
even across different spells. Note that modifying the content
of a shared table does not update the content for other
SharedVars.
This constructor does not update the shared value. This has
the negative side effect that the first call to
'SharedVar:getValue()' may block indefinately if there is no
other SharedVar with the same name, because the SharedVar
is stuck waiting for the previous value. To avoid this risk
consider using 'SharedVar.new' instead.

Parameters:
  - name: the public name for the new SharedVar
]]

function SharedVar:respondToNewConnections()
  if self.connecting then
    return
  end
  local queue = self.requestQueue
  local event = queue:pop(0)
  if event then
    queue:clear()
    self:fireUpdate(self.value)
  end
end

function SharedVar:getValue()
  local queue = self.updateQueue
  if self.connecting then
    local event = queue:pop() -- blocking on first read
    self.value = event.data
    self.connecting = nil
  end
  while not queue:isEmpty() do
    local event = queue:pop(0)
    if queue:isEmpty() then
      self.value = event.data
    end
  end
  return self.value
end

function SharedVar:setValue(value)
  self:fireUpdate(value)
end

function SharedVar:fireUpdate(newValue)
  Events.fire(updateEventName..self.name, newValue)
end

function SharedVar:close()
  self.requestQueue:disconnect()
  self.updateQueue:disconnect()
end