[fpc-devel] Proposed change in simpleipc

[Luiz Americo Pereira Camara]

While developing with simpleipc i found that there's no straightforward 
way to identify the type of a message (see the forth paragraph of 
http://lazarusroad.blogspot.com/2006/12/only-one-instance.html), so i 
looked what i could do to improve it.

Currently,  TMessageType is defined as an enum type with two possible 
values: mtString and mtUnknow. If you use SendMessage mtUnknow is used 
if SendMessageString is used mtString is used. But the message type is 
not being used:  under windows the message type is not even passed to 
the server, under linux is passed but not used.

What i propose is simple: change the TMessageType to an 32bit ordinal 
type (longint or longword), provide ways the user to send custom message 
types and add a MsgType property to IPCServer. This way the  user 
(programmer) can send messages with different purposes and easily know 
what to do when they arrive. Some thing like that:

with IPCServer do
  begin
    case MsgType of
      mtString:;
      mtMyType1:;
      mtMyType2:;
    end;
  end;

The patch i'm sending does:

 - Change TMessageType to longint
 - Define mtString and mtUnknow as constants
 - Add overloaded methods SendMessage and SendMessageString with an 
extra parameter (MsgType)
 - Added MsgType property to TSimpleIPCServer
 - Changed some capitalizations

win32
 - MsgType is passed through an unused CopyDataStruct field

unix:
 - No changes at all, just fixed a bug (mtString was used always)

Notice that there's no memory or resource increase since the patch uses 
previously unused resources.
I'm sending also a test program written in Lazarus. It was tested under 
win32 and linux (ubuntu 10.06)


Luiz

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