Selfmade Critical Sections
Posted: Thu Apr 28, 2005 2:54 pm
Yeah, I know there are lots of APIs, but they are all ugly, slow and require (of course) the windows dlls. Cause someone told me, it would be impossible to find an other way to manage "Critical Sections", I wrote this code to show him the opposite.
What are Critical Sections
They are useful, when you do much memory access.. When you (for example) change a string from multiple processes, your program will crash when you dont use it.
How it works
- In the Enter-procedure every thread receives an unique number, this is guaranteed by the XADD command, which reads and modifies the variable in one call.
- Then the Thread waits, until its his turn
- When the Thread finished, we increase the current Thread-Index, so that the next threads enters the section
EDIT: Just published another way to do this in the german forum.. here it is!
Advantage:
* Works also with Multiprocessor-Systems
* You can kill threads with KillThread()/TerminateThread_(), when the commands are inside a CriticalSection! The first code would make problems in some cases!
Here also the link to the thread in the german forum: http://forums.purebasic.com/german/viewtopic.php?t=3061
What are Critical Sections
They are useful, when you do much memory access.. When you (for example) change a string from multiple processes, your program will crash when you dont use it.
How it works
- In the Enter-procedure every thread receives an unique number, this is guaranteed by the XADD command, which reads and modifies the variable in one call.
- Then the Thread waits, until its his turn
- When the Thread finished, we increase the current Thread-Index, so that the next threads enters the section
Code: Select all
;-
;- PureFan's Critical Sections *SPECIAL*
;-
;- Posted in: English PureBasic Board
;- Date: 28.04.05
;-
Structure Pure_CS
In.l
Out.l
EndStructure
Procedure Pure_InitCS(*PCS.Pure_CS)
*PCS\In=0
*PCS\Out=0
EndProcedure
Procedure Pure_EnterCS(*PCS.Pure_CS)
!POP Edi
!PUSH Edi
!XOR Esi,Esi
!INC Esi
!XADD [Edi],Esi
!.loop:
!PUSH dword 1
!CALL _Sleep@4
!CMP [Edi+4],Esi
!JNE .loop
EndProcedure
Procedure Pure_LeaveCS(*PCS.Pure_CS)
!POP Edi
!PUSH Edi
!INC dword[Edi+4]
EndProcedure
;/
;/ Example for PureFan's Critical Sections
;/
Global SichereStrings.Pure_CS
Pure_InitCS(SichereStrings)
Global GlobalerString.s
Procedure String_Thread(Parameter)
Repeat
Pure_EnterCS(SichereStrings)
lokaler_string.s=GlobalerString+"hallo"
GlobalerString.s=Right(lokaler_string.s,100)
Pure_LeaveCS(SichereStrings)
ForEver
EndProcedure
For I=1 To 10
CreateThread(@String_Thread(),I)
Next I
Repeat
Pure_EnterCS(SichereStrings)
lokaler_string.s=GlobalerString+"hallo"
GlobalerString.s=Right(lokaler_string.s,100)
Pure_LeaveCS(SichereStrings)
ForEver
EDIT: Just published another way to do this in the german forum.. here it is!
Advantage:
* Works also with Multiprocessor-Systems
* You can kill threads with KillThread()/TerminateThread_(), when the commands are inside a CriticalSection! The first code would make problems in some cases!
Code: Select all
;-
;- PureFan's Critical Sections *SPECIAL*
;-
;- Posted in: English PureBasic Board
;- Date: 30.04.05
;-
Structure Pure_CS
Cnt.l
EndStructure
Procedure Pure_InitCS(*PCS.Pure_CS)
*PCS\Cnt=0
EndProcedure
Procedure Pure_EnterCS(*PCS.Pure_CS)
!POP Edi
!PUSH Edi
!.loop:
!PUSH dword 1
!CALL _Sleep@4
!MOV Esi,1
!XCHG [Edi],Esi
!CMP Esi,0
!JNE .loop
EndProcedure
Procedure Pure_LeaveCS(*PCS.Pure_CS)
!POP Edi
!PUSH Edi
!MOV dword [Edi],0
EndProcedure
;/
;/ Example for PureFan's Critical Sections
;/
Global SichereStrings.Pure_CS
Pure_InitCS(SichereStrings)
Global GlobalerString.s
Procedure String_Thread(Parameter)
Repeat
Pure_EnterCS(SichereStrings)
lokaler_string.s=GlobalerString+"hallo"
GlobalerString.s=Right(lokaler_string.s,100)
Pure_LeaveCS(SichereStrings)
ForEver
EndProcedure
For I=1 To 10
CreateThread(@String_Thread(),I)
Next I
Repeat
Pure_EnterCS(SichereStrings)
lokaler_string.s=GlobalerString+"hallo"
GlobalerString.s=Right(lokaler_string.s,100)
Pure_LeaveCS(SichereStrings)
ForEver
Here also the link to the thread in the german forum: http://forums.purebasic.com/german/viewtopic.php?t=3061
Just published a second method! (see above)