From ccc592df50d217757d74cb343d046a92d76860c1 Mon Sep 17 00:00:00 2001
From: sebres <sebres@users.sourceforge.net>
Date: Thu, 16 May 2019 17:49:25 +0000
Subject: timerate: allow continue from measurement cycle (used for conditional
 flow control of iterations); more gentle evaluation behaviour, similar to a
 cycle now (also avoids extra overhead to set result to interp, etc.); todo:
 rewrite optimization of INST_DONE using last-instruction pointer or
 optimization flags for compile of iteration (if sebres's perf-branch gets
 merged).

---
 generic/tclCmdMZ.c | 40 +++++++++++++++++++++++++---------------
 tests/cmdMZ.test   |  8 ++++++++
 2 files changed, 33 insertions(+), 15 deletions(-)

diff --git a/generic/tclCmdMZ.c b/generic/tclCmdMZ.c
index fe5e51c..6be5087 100644
--- a/generic/tclCmdMZ.c
+++ b/generic/tclCmdMZ.c
@@ -4193,6 +4193,14 @@ Tcl_TimeRateObjCmd(
 	}
 	codePtr = TclCompileObj(interp, objPtr, NULL, 0);
 	TclPreserveByteCode(codePtr);
+	/* 
+	 * Replace last compiled done instruction with continue: it's a part of
+	 * iteration, this way evaluation will be more similar to a cycle (also
+	 * avoids extra overhead to set result to interp, etc.)
+	 */
+	if (codePtr->codeStart[codePtr->numCodeBytes-1] == INST_DONE) {
+	    codePtr->codeStart[codePtr->numCodeBytes-1] = INST_CONTINUE;
+	}
     }
 
     /*
@@ -4237,23 +4245,25 @@ Tcl_TimeRateObjCmd(
 	    } else {			/* eval */
 		result = TclEvalObjEx(interp, objPtr, 0, NULL, 0);
 	    }
-	    if (result != TCL_OK) {
-		/*
-		 * Allow break from measurement cycle (used for conditional
-		 * stop).
-		 */
+	    /*
+	     * Allow break and continue from measurement cycle (used for
+	     * conditional stop and flow control of iterations).
+	     */
 
-		if (result != TCL_BREAK) {
+	    switch (result) {
+		case TCL_OK:
+		    break;
+		case TCL_BREAK:
+		    /*
+		     * Force stop immediately.
+		     */
+		    threshold = 1;
+		    maxcnt = 0;
+		case TCL_CONTINUE:
+		    result = TCL_OK;
+		    break;
+		default:
 		    goto done;
-		}
-
-		/*
-		 * Force stop immediately.
-		 */
-
-		threshold = 1;
-		maxcnt = 0;
-		result = TCL_OK;
 	    }
 
 	    /*
diff --git a/tests/cmdMZ.test b/tests/cmdMZ.test
index 4c4f532..09fff07 100644
--- a/tests/cmdMZ.test
+++ b/tests/cmdMZ.test
@@ -412,6 +412,14 @@ test cmdMZ-6.8 {Tcl_TimeRateObjCmd: allow (conditional) break from timerate} {
 	[expr {[lindex $m1 4] > 1000}] \
 	[expr {[lindex $m1 6] < 10}]
 } {1 1 1 1}
+test cmdMZ-6.8.1 {Tcl_TimeRateObjCmd: allow (conditional) continue in timerate} {
+    set m1 [timerate {continue; return -code error "unexpected"} 1000 10]
+    list \
+    [expr {[lindex $m1 0] < 1000}] \
+    [expr {[lindex $m1 2] == 10}] \
+    [expr {[lindex $m1 4] > 1000}] \
+    [expr {[lindex $m1 6] < 100}]
+} {1 1 1 1}
 test cmdMZ-6.9 {Tcl_TimeRateObjCmd: max count of iterations} {
     set m1 [timerate {} 1000 5];	# max-count wins
     set m2 [timerate {_nrt_sleep 20} 1 5];	# max-time wins
-- 
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