TS: Use finite timeout only when threadqueue has run empty

Before the timeout constant was used always, such that ThreadGroupGetDFR
waited at least once with the timeout for the case the thread queue was read empty.
This wait is not necessary as the thread queue can be checked for emptiness also
with a zero timeout.

TS_GetNewestFromThreadQueue and TS_GetNewestFromThreadQueueMult use now a timeout of
zero for reading the thread queue empty and for the then first check of emptyness,
where ThreadGroupGetDFR returns a null DFR. Only further read attempts,
if timeout_retries are set, use the TS_GET_REPEAT_TIMEOUT_IN_MS.

Author: MichaelHuth

Packages/MIES/MIES_ThreadsafeUtilities.ipf

@@ -19,7 +19,7 @@ static Constant TS_ERROR_INVALID_TGID       = 980 // Invalid Thread Group ID or
 /// Throws away anything else in the datafolder from the thread queue.
 Function TS_GetNewestFromThreadQueue(variable tgID, string varName, [variable timeout_default, variable timeout_tries])
 
-	variable var, err, i
+	variable var, err, i, timeout
 
 	ASSERT_TS(!isEmpty(varName), "varName must not be empty")
 
@@ -41,7 +41,7 @@ Function TS_GetNewestFromThreadQueue(variable tgID, string varName, [variable ti
 
 	for(i = 0; i < timeout_tries; i += 1)
 		AssertOnAndClearRTError()
-		DFREF dfr = ThreadGroupGetDFR(tgID, TS_GET_REPEAT_TIMEOUT_IN_MS); err = GetRTError(1)
+		DFREF dfr = ThreadGroupGetDFR(tgID, timeout); err = GetRTError(1)
 
 		if(err)
 			ASSERT(err == TS_ERROR_INVALID_TGID, "Unexpected error value of " + num2str(err))
@@ -54,8 +54,11 @@ Function TS_GetNewestFromThreadQueue(variable tgID, string varName, [variable ti
 			elseif(TS_ThreadGroupFinished(tgID))
 				return NaN
 			else
+				timeout = TS_GET_REPEAT_TIMEOUT_IN_MS
 				continue
 			endif
+		else
+			timeout = 0
 		endif
 
 		NVAR/Z/SDFR=dfr var_thread = $varName
@@ -77,7 +80,7 @@ End
 /// Throws away anything else in the datafolder from the thread queue.
 Function/WAVE TS_GetNewestFromThreadQueueMult(variable tgID, WAVE/T varNames, [variable timeout_default, variable timeout_tries])
 
-	variable numEntries, i, j, oneValidEntry, err
+	variable numEntries, i, j, oneValidEntry, err, timeout
 	string varName
 
 	ASSERT_TS(DimSize(varNames, COLS) == 0, "Expected a 1D wave")
@@ -108,7 +111,7 @@ Function/WAVE TS_GetNewestFromThreadQueueMult(variable tgID, WAVE/T varNames, [v
 
 	for(i = 0; i < timeout_tries; i += 1)
 		AssertOnAndClearRTError()
-		DFREF dfr = ThreadGroupGetDFR(tgID, TS_GET_REPEAT_TIMEOUT_IN_MS); err = GetRTError(1)
+		DFREF dfr = ThreadGroupGetDFR(tgID, timeout); err = GetRTError(1)
 
 		if(err)
 			ASSERT(err == TS_ERROR_INVALID_TGID, "Unexpected error value of " + num2str(err))
@@ -119,12 +122,15 @@ Function/WAVE TS_GetNewestFromThreadQueueMult(variable tgID, WAVE/T varNames, [v
 			if(TS_ThreadGroupFinished(tgID))
 				return $""
 			elseif(!oneValidEntry)
+				timeout = TS_GET_REPEAT_TIMEOUT_IN_MS
 				continue
 			endif
 
 			return result
 		endif
 
+		timeout = 0
+
 		for(j = 0; j < numEntries; j += 1)
 			NVAR/Z/SDFR=dfr var = $GetDimLabel(result, ROWS, j)