rerouterator/osc.lua

local osc = {}
local numberConverter = require("numberConverter")
local messageMetatable = {
  __index = function(self, index)
    if index ~= "pack" and index ~= "unpack" then
      return osc[index]
    end
  end,
}

function osc.toOSCString(original)
  local valid = #original % 4 == 0 
  valid = valid and original:sub(#original) == string.char(0)
  -- we should not attempt to make an already valid osc string into an osc string
  if not valid then
    local newstr = original .. '\0'
    while ((#newstr)) % 4 ~= 0 do
      newstr = newstr .. '\0'
    end
    return newstr
  else
    return original
  end
end

function osc.appendArgument(self, newArgument, knownType)
  if knownType then
    self.argString = self.argString .. knownType
    table.insert(self, newArgument)
  else
    -- type check and update arg string
    if type(newArgument) == "number" then
      if newArgument == math.floor(newArgument) then
        self.argString = self.argString .. "i"
        table.insert(self, numberConverter.toNetworkInt(newArgument))
      else
        self.argString = self.argString .. "f"
        table.insert(self, numberConverter.toNetworkFloat(newArgument))
      end
    elseif type(newArgument) == "string" then

      self.argString = self.argString .. "s"
      table.insert(self, osc.toOSCString(newArgument))
    else
      error("invalid type for OSC message: " .. type(newArgument))
    end
  end
end

function osc.getArgument(self, index)
  local type = self.argString:sub(index+1,index+1)
  if type == 'i' then
    return numberConverter.intToLuaNumber(self[index])
  elseif type == 'f' then
    return numberConverter.floatToLuaNumber(self[index])
  elseif type == 's' then
    return self[index]:match("[^%z]*")
  else
    error("this should be impossible")
  end
end

function osc.unpack(rawDataGram)
  local msg = {}
  setmetatable(msg,messageMetatable)

  -- grab address
  -- this nifty patter to match OSC strings only works if you know there is a non-zero character after
  local addressStart, addressEnd = rawDataGram:find("[^%z]+%z+")
  msg.addr = rawDataGram:sub(addressStart, addressEnd)

  -- grab argString
  msg.argString = rawDataGram:match("[^%z]+", addressEnd+1)

  --       start of arg       len of str       offset for the nulls
  argEnd = addressEnd +  #msg.argString + (4 - #msg.argString % 4)
  
  -- grab the arguments
  local dataStart = argEnd+1

  for index=1,#msg.argString,1 do
    local c = msg.argString:sub(index,index)

    -- we treat each type a bit differently
    if (c ~= '\0' and c ~= ',') then
      if (c == 'i') then
        msg[index-1] = rawDataGram:sub(dataStart, dataStart+3)
        dataStart = dataStart + 4
      elseif (c == 'f') then
        msg[index-1] = rawDataGram:sub(dataStart, dataStart+3)
        dataStart = dataStart + 4
      elseif (c == 's') then
        local stringEnd = rawDataGram:find(string.char(0), dataStart)
        local stringLen = stringEnd - dataStart + 1
        local dataLen = stringLen + (4-stringLen%4)
        local dataEnd = dataStart + dataLen - 1
        msg[index-1] = rawDataGram:sub(dataStart,dataEnd)
        dataStart = dataEnd + 1
      end
      -- maybe a case fore timestamp
      -- maybe a case for blobs but i probably dont care
    end
  end

  return msg
end

-- packs our message table back into a string that is ready to get shot over the network
function osc.pack(tbl)
  local oscMessage = tbl.addr .. osc.toOSCString(tbl.argString)
  for i=1, #tbl, 1 do
    oscMessage = oscMessage .. tbl[i]
  end
  return oscMessage
end

function osc.create(addr, ...)
  local arg = {...}
  local msg = {
    addr = osc.toOSCString(addr),
    argString = ",",
  }

  for _, a in pairs(arg) do
    osc.appendArgument(msg,a)
  end

  return msg
end

return osc