Some buffering in Lua side RPC logic to speed things up.

Flush remaining unexpected data before sending new messages.

src/main/resources/data/oc2/file_systems/scripts/lua/devices.lua

@@ -74,53 +74,90 @@ DeviceBus.__index = DeviceBus
 
 local message_delimiter = string.char(0)
 
-local function parseError(result)
-  if result.type == "error" then
+local function parseError(result, reason)
+  if result and result.type == "error" then
     return result.data
+  elseif result then
+    return "unexpected message type: " .. result.type
   else
-    return "unexpected message type " .. result.type
+    return "unexpected error: " .. (reason or "unknown error")
   end
 end
 
-local function readOne(fd)
-  local result, status, errnum = poll.rpoll(fd, 10)
-  if result == 1 then
-    return unistd.read(fd, 1)
-  else
+local function skipInput(bus)
+  repeat
+    local result, status, errnum = poll.rpoll(bus.fd, 0)
+    if result == 1 then
+      unistd.read(bus.fd, 1024)
+    end
+  until result ~= 1
+end
+
+local function fillBuffer(bus)
+  local result, status, errnum = poll.rpoll(bus.fd, -1)
+  if result == nil then
     return result, status, errnum
+  elseif result == 0 then
+    return nil, "timeout"
+  else
+    bus.buffer = unistd.read(bus.fd, 1024)
+    bus.bufferLen = string.len(bus.buffer)
+    bus.bufferPos = 1
+    return true
   end
 end
 
-local function readMessage(device)
+local function clearBuffer(bus)
+    bus.buffer = nil
+end
+
+local function readOne(bus)
+  if not bus.buffer then
+    local result, status = fillBuffer(bus)
+    if not result then
+      return result, status
+    end
+  end
+
+  local result = bus.buffer:byte(bus.bufferPos)
+  if bus.bufferPos >= bus.bufferLen then
+    bus.buffer = nil
+  else
+    bus.bufferPos = bus.bufferPos + 1
+  end
+
+  return result
+end
+
+local function readMessage(bus)
   local value
   local message = ""
   while true do
-    value = readOne(device.fd)
-    if not value then
-      unistd.sleep(1)
+    value, reason = readOne(bus)
+    if value == nil then -- error
+      return value, reason
     else
-      if value == message_delimiter or value == 0 then
+      if value == 0 then
         if message:match("%S") ~= nil then
           local ok, result = pcall(cjson.decode, message)
           if ok then
             return result
+          else
+            return nil, result
           end
         else
           message = ""
         end
       else
-        message = message .. value
+        message = message .. string.char(value)
       end
     end
   end
 end
 
-local function writeMessage(device, data)
+local function writeMessage(bus, data)
   local message = cjson.encode(data)
-  return unistd.write(device.fd,
-      message_delimiter ..
-          message ..
-          message_delimiter)
+  return unistd.write(bus.fd, message_delimiter .. message .. message_delimiter)
 end
 
 function DeviceBus:new(path)
@@ -138,13 +175,19 @@ function DeviceBus:close()
   unistd.close(self.fd)
 end
 
+function DeviceBus:flush()
+  clearBuffer(self)
+  skipInput(self)
+end
+
 function DeviceBus:list()
+  self:flush()
   writeMessage(self, { type = "list" })
-  local result = readMessage(self)
-  if result.type == "list" then
+  local result, reason = readMessage(self)
+  if result and result.type == "list" then
     return result.data
   else
-    return nil, parseError(result)
+    return error(parseError(result))
   end
 end
 
@@ -183,26 +226,28 @@ function DeviceBus:find(deviceTypeName)
 end
 
 function DeviceBus:methods(deviceId)
+  self:flush()
   writeMessage(self, { type = "methods", data = deviceId })
-  local result = readMessage(self)
-  if result.type == "methods" then
+  local result, reason = readMessage(self)
+  if result and result.type == "methods" then
     return result.data
   else
-    error(parseError(result))
+    error(parseError(result, reason))
   end
 end
 
 function DeviceBus:invoke(deviceId, methodName, ...)
+  self:flush()
   writeMessage(self, { type = "invoke", data = {
     deviceId = deviceId,
     name = methodName,
     parameters = { ... }
-  } })
-  local result = readMessage(self)
-  if result.type == "result" then
+  }})
+  local result, reason = readMessage(self)
+  if result and result.type == "result" then
     return result.data
   else
-    error(parseError(result))
+    error(parseError(result, reason))
   end
 end