Add QElapsedTimer::nsecsElapsed() const

Allow sub-millisecond resolution on systems where it is possible. On UNIX,
with monotonic clock support we get full nanosecond resolution, microsecond
otherwise. On Windows we convert the performance counters to nanoseconds if
availble, otherwise we only have millisecond resolution. On Mac, the mach time
is converted to nanoseconds. On Symbian, we have microsecond resolution.

Reviewed-by: joao

6 files changed, 58 insertions, 18 deletions

diff --git a/src/corelib/tools/qelapsedtimer.h b/src/corelib/tools/qelapsedtimer.h
index b996f6abab..4118389e9e 100644
--- a/src/corelib/tools/qelapsedtimer.h
+++ b/src/corelib/tools/qelapsedtimer.h
@@ -68,6 +68,7 @@ public:
     void invalidate();
     bool isValid() const;
 
+    qint64 nsecsElapsed() const;
     qint64 elapsed() const;
     bool hasExpired(qint64 timeout) const;
 
diff --git a/src/corelib/tools/qelapsedtimer_generic.cpp b/src/corelib/tools/qelapsedtimer_generic.cpp
index 85986e6e3f..740f496fa3 100644
--- a/src/corelib/tools/qelapsedtimer_generic.cpp
+++ b/src/corelib/tools/qelapsedtimer_generic.cpp
@@ -103,6 +103,22 @@ qint64 QElapsedTimer::restart()
     return t1 - old;
 }
 
+/*! \since 4.8
+
+    Returns the number of nanoseconds since this QElapsedTimer was last
+    started. Calling this function in a QElapsedTimer that was invalidated
+    will result in undefined results.
+
+    On platforms that do not provide nanosecond resolution, the value returned
+    will be the best estimate available.
+
+    \sa start(), restart(), hasExpired(), invalidate()
+*/
+qint64 QElapsedTimer::nsecsElapsed() const
+{
+    return elapsed() * 1000000;
+}
+
 /*!
     Returns the number of milliseconds since this QElapsedTimer was last
     started. Calling this function in a QElapsedTimer that was invalidated
diff --git a/src/corelib/tools/qelapsedtimer_mac.cpp b/src/corelib/tools/qelapsedtimer_mac.cpp
index 8fceb49324..e51f8b32f0 100644
--- a/src/corelib/tools/qelapsedtimer_mac.cpp
+++ b/src/corelib/tools/qelapsedtimer_mac.cpp
@@ -97,6 +97,12 @@ qint64 QElapsedTimer::restart()
     return absoluteToMSecs(t1 - old);
 }
 
+qint64 QElapsedTimer::nsecsElapsed() const
+{
+    uint64_t cpu_time = mach_absolute_time();
+    return absoluteToNSecs(cpu_time - t1);
+}
+
 qint64 QElapsedTimer::elapsed() const
 {
     uint64_t cpu_time = mach_absolute_time();
diff --git a/src/corelib/tools/qelapsedtimer_symbian.cpp b/src/corelib/tools/qelapsedtimer_symbian.cpp
index 038b1029b7..7cd5f1e1b1 100644
--- a/src/corelib/tools/qelapsedtimer_symbian.cpp
+++ b/src/corelib/tools/qelapsedtimer_symbian.cpp
@@ -64,11 +64,6 @@ static quint64 getMicrosecondFromTick()
     return nanokernel_tick_period * (val | (quint64(highdword) << 32));
 }
 
-static quint64 getMillisecondFromTick()
-{
-    return getMicrosecondFromTick() / 1000;
-}
-
 timeval qt_gettime()
 {
     timeval tv;
@@ -91,36 +86,41 @@ bool QElapsedTimer::isMonotonic()
 
 void QElapsedTimer::start()
 {
-    t1 = getMillisecondFromTick();
+    t1 = getMicrosecondFromTick();
     t2 = 0;
 }
 
 qint64 QElapsedTimer::restart()
 {
     qint64 oldt1 = t1;
-    t1 = getMillisecondFromTick();
+    t1 = getMicrosecondFromTick();
     t2 = 0;
     return t1 - oldt1;
 }
 
+qint64 QElapsedTimer::nsecsElapsed() const
+{
+    return (getMicrosecondFromTick() - t1) * 1000;
+}
+
 qint64 QElapsedTimer::elapsed() const
 {
-    return getMillisecondFromTick() - t1;
+    return (getMicrosecondFromTick() - t1) / 1000;
 }
 
 qint64 QElapsedTimer::msecsSinceReference() const
 {
-    return t1;
+    return t1 / 1000;
 }
 
 qint64 QElapsedTimer::msecsTo(const QElapsedTimer &other) const
 {
-    return other.t1 - t1;
+    return (other.t1 - t1) / 1000;
 }
 
 qint64 QElapsedTimer::secsTo(const QElapsedTimer &other) const
 {
-    return msecsTo(other) / 1000;
+    return msecsTo(other) / 1000000;
 }
 
 bool operator<(const QElapsedTimer &v1, const QElapsedTimer &v2)
diff --git a/src/corelib/tools/qelapsedtimer_unix.cpp b/src/corelib/tools/qelapsedtimer_unix.cpp
index 633fa00d95..7407e1b5a9 100644
--- a/src/corelib/tools/qelapsedtimer_unix.cpp
+++ b/src/corelib/tools/qelapsedtimer_unix.cpp
@@ -167,6 +167,17 @@ qint64 QElapsedTimer::restart()
     return elapsedAndRestart(t1, t2, &t1, &t2);
 }
 
+qint64 QElapsedTimer::nsecsElapsed() const
+{
+    qint64 sec, frac;
+    do_gettime(&sec, &frac);
+    sec = sec - t1;
+    frac = frac - t2;
+    if (!monotonicClockAvailable)
+        frac *= 1000;
+    return sec * Q_INT64_C(1000000000) + frac;
+}
+
 qint64 QElapsedTimer::elapsed() const
 {
     qint64 sec, frac;
diff --git a/src/corelib/tools/qelapsedtimer_win.cpp b/src/corelib/tools/qelapsedtimer_win.cpp
index c77acaa15f..3f4acc14ab 100644
--- a/src/corelib/tools/qelapsedtimer_win.cpp
+++ b/src/corelib/tools/qelapsedtimer_win.cpp
@@ -79,14 +79,14 @@ static void resolveLibs()
     done = true;
 }
 
-static inline qint64 ticksToMilliseconds(qint64 ticks)
+static inline qint64 ticksToNanoseconds(qint64 ticks)
 {
     if (counterFrequency > 0) {
         // QueryPerformanceCounter uses an arbitrary frequency
-        return ticks * 1000 / counterFrequency;
+        return ticks * 1000000000 / counterFrequency;
     } else {
         // GetTickCount(64) return milliseconds
-        return ticks;
+        return ticks * 1000000;
     }
 }
 
@@ -144,24 +144,30 @@ qint64 QElapsedTimer::restart()
     qint64 oldt1 = t1;
     t1 = getTickCount();
     t2 = 0;
-    return ticksToMilliseconds(t1 - oldt1);
+    return ticksToNanoseconds(t1 - oldt1) / 1000000;
+}
+
+qint64 QElapsedTimer::nsecsElapsed() const
+{
+    qint64 elapsed = getTickCount() - t1;
+    return ticksToNanoseconds(elapsed);
 }
 
 qint64 QElapsedTimer::elapsed() const
 {
     qint64 elapsed = getTickCount() - t1;
-    return ticksToMilliseconds(elapsed);
+    return ticksToNanoseconds(elapsed) / 1000000;
 }
 
 qint64 QElapsedTimer::msecsSinceReference() const
 {
-    return ticksToMilliseconds(t1);
+    return ticksToNanoseconds(t1) / 1000000;
 }
 
 qint64 QElapsedTimer::msecsTo(const QElapsedTimer &other) const
 {
     qint64 difference = other.t1 - t1;
-    return ticksToMilliseconds(difference);
+    return ticksToNanoseconds(difference) / 1000000;
 }
 
 qint64 QElapsedTimer::secsTo(const QElapsedTimer &other) const