Is there some way to search the in buffer on a serial port for a specific 
character without removing or changing any characters?

On 04/14/2010 01:50 PM, Al Wimberly wrote:
> Is there some way to search the in buffer on a serial port for a specific 
> character without removing or changing any characters?
> 
>  
> 
> 
What are you using to control the serial port?

Jim

Hello Al,

This goes back to Clipper 5.x with Clipper tools.
In those old days, you were able to use:
cData	:= Com_Read( 1  , ,.T.)
This read the com buffer, but the buffer was not cleared.
So you could Com_Read(1,,.F.) and read the same buffer again (and clears 
the read buffer).

Unfortunaly this option is not availeble in Xbase++ tools.
The help says:

Com_Read( <nComPortNum>   , ;
           [<nBytesToRead>], ;
           <ignored>         ;

         ) --> cString

NOTE: The CA-Tools function allows a third parameter that specifies 
whether or not the bytes are to be deleted from the receive buffer. This 
feature cannot be provided and the third parameter is ignored.

However, there is a workarround.
Create a thread that reads the COM input port continuesly, and build 
your own read-buffer.
Then in another thread you can monitor / read the COM device.

See speudo code below, that should point you in the right direction.

Regards, Jack Duijf

Procedure Main()

LOCAL nPort := 1
LOCAL oComm := ComPort():New(nPort)
oComm:Start()
Do while Inkey(.1) <> 27
    if oComm:TestBuffer("Hello")
       ? oComm:GetBuffer()
    endif
Enddo
oComm:Terminate()
Return

CLASS ComPort From Thread
HIDDEN:
VAR   lAbort
VAR   cBuffer
VAR   lTerminated
EXPORTED
METHOD Init
SYNC METHOD TestBuffer
SYNC METHOD GetBuffer
SYNC METHOD AddToBuffer
METHOD Execute
METHOD Terminate
Endclass

METHOD ComPort:Init(nPort)
Thread:init()
...
Com_open(...)
...
Return SELF

METHOD ComPort:Execute()
::lAbort := FALSE
::lTerminated := FALSE
nRead := 0
Do while !lAbort
    if (nRead := Com_Count(nPort)) > 0
       ::AddToBuffer(Com_Read(nPort))
    else
       Sleep(10)
    endif
enddo
::lTerminate := TRUE
Com_Close(...)
Return

METHOD Comport:Terminate()
::lAbort := TRUE
Do while !::lTerminated
    Sleep(5)
Enddo
Return

METHOD Comport:AddToBuffer(cData)
::cBuffer += cData
Return

METHOD Comport:TestBuffer(cData)
Return (cData $ ::cBuffer)

METHOD Comport:GetBuffer(nLen)
LOCAL cRet := ""
Default nLen To Len(::cBuffer)
nLen := Min(nLen,Len(::cBuffer))
cRet := Substr(::cBuffer,1,nLen)
::cBuffer := Substr(::cBuffer,nLen+1)
Return cRet




Op 14-4-2010 19:50, Al Wimberly schreef:
> Is there some way to search the in buffer on a serial port for a specific
> character without removing or changing any characters?
>
>
>
>