add TimeBoxer class

4 files changed, 98 insertions, 0 deletions

diff --git a/vespalib/src/vespa/vespalib/CMakeLists.txt b/vespalib/src/vespa/vespalib/CMakeLists.txt
index 22a654b02b7..7372288a64c 100644
--- a/vespalib/src/vespa/vespalib/CMakeLists.txt
+++ b/vespalib/src/vespa/vespalib/CMakeLists.txt
@@ -14,6 +14,7 @@ vespa_add_library(vespalib
     $<TARGET_OBJECTS:vespalib_vespalib_stllike>
     $<TARGET_OBJECTS:vespalib_vespalib_testkit>
     $<TARGET_OBJECTS:vespalib_vespalib_text>
+    $<TARGET_OBJECTS:vespalib_vespalib_time>
     $<TARGET_OBJECTS:vespalib_vespalib_trace>
     $<TARGET_OBJECTS:vespalib_vespalib_util>
     $<TARGET_OBJECTS:vespalib_vespalib_websocket>
diff --git a/vespalib/src/vespa/vespalib/time/CMakeLists.txt b/vespalib/src/vespa/vespalib/time/CMakeLists.txt
new file mode 100644
index 00000000000..8c24e7b9e5e
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/time/CMakeLists.txt
@@ -0,0 +1,6 @@
+# Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+vespa_add_library(vespalib_vespalib_time OBJECT
+    SOURCES
+    time_boxer.cpp
+    DEPENDS
+)
diff --git a/vespalib/src/vespa/vespalib/time/time_boxer.cpp b/vespalib/src/vespa/vespalib/time/time_boxer.cpp
new file mode 100644
index 00000000000..df057fc4ccf
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/time/time_boxer.cpp
@@ -0,0 +1,20 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+#include "time_boxer.h"
+
+#if 0
+
+#include <time.h>
+#include <unistd.h>
+#include <stdio.h>
+
+int main(int, char **)
+{
+    vespalib::TimeBoxer tb(3.0);
+    while (tb.hasTimeLeft()) {
+        double tl = tb.timeLeft();
+        printf("time left: %g seconds\n", tl);
+        sleep(1);
+    }
+}
+
+#endif
diff --git a/vespalib/src/vespa/vespalib/time/time_boxer.h b/vespalib/src/vespa/vespalib/time/time_boxer.h
new file mode 100644
index 00000000000..b5ac6a8ed82
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/time/time_boxer.h
@@ -0,0 +1,71 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+#pragma once
+
+#include <chrono>
+
+namespace vespalib {
+
+/**
+ * Simple utility for time boxing your activity
+ *
+ * <pre>
+ * Example:
+ *
+ * TimeBoxer timebox(5.0);
+ * while (timebox.hasTimeLeft()) {
+ *   ... do stuff
+ *   ... do stuff with timeout(timebox.timeLeft())
+ * }
+ * </pre>
+ **/
+class TimeBoxer
+{
+private:
+    using clock = std::conditional<std::chrono::high_resolution_clock::is_steady,
+                                   std::chrono::high_resolution_clock,
+                                   std::chrono::steady_clock>::type;
+
+    using seconds = std::chrono::duration<double, std::ratio<1,1>>;
+
+    template<typename DURATION>
+    static inline clock::duration to_internal(DURATION x) {
+        return std::chrono::duration_cast<clock::duration>(x);
+    }
+
+    template<typename DURATION>
+    static inline double to_external(DURATION x) {
+        return std::chrono::duration_cast<seconds>(x).count();
+    }
+
+    clock::time_point _end_time;
+
+public:
+    /**
+     * Construct a TimeBoxer with a given budget from now
+     * @param budget amount of time in seconds
+     **/
+    explicit TimeBoxer(double budget)
+        : _end_time(clock::now() + to_internal(seconds(budget)))
+    {
+    }
+
+    /**
+     * @return true if there is time left in the budget
+     **/
+    bool hasTimeLeft() {
+        return clock::now() < _end_time;
+    }
+
+    /**
+     * @return the seconds left before the budget elapses
+     **/
+    double timeLeft() {
+        clock::time_point now = clock::now();
+        if (now < _end_time) {
+            return to_external(_end_time - now);
+        }
+        return 0.0;
+    }
+};
+
+} // namespace vespalib