1 files changed, 168 insertions, 0 deletions
diff --git a/src/timer.cpp b/src/timer.cpp
new file mode 100644
index 0000000..22015ff
--- /dev/null
+++ b/src/timer.cpp
@@ -0,0 +1,168 @@
+/*******************************************************************************
+ * Copyright (c) 2006 International Business Machines Corporation.             *
+ * All rights reserved. This program and the accompanying materials            *
+ * are made available under the terms of the Common Public License v1.0        *
+ * which accompanies this distribution, and is available at                    *
+ * http://www.opensource.org/licenses/cpl1.0.php                               *
+ *                                                                             *
+ * Contributors:                                                               *
+ *    Douglas M. Pase - initial API and implementation                         *
+ *******************************************************************************/
+
+//
+// Configuration
+//
+
+// Implementation header
+#include "timer.h"
+
+// System includes
+#include <cstdio>
+#include <sys/time.h>
+
+static int64 read_rtc();
+static void calibrate_rtc(int n);
+static double wall_seconds();
+
+static int wall_ticks = -1;
+static int rtc_ticks = -1;
+static double wall_elapsed = -1;
+static int64 rtc_elapsed = -1;
+static double time_factor = -1;
+
+#if !defined(RTC) && !defined(GTOD)
+#define RTC
+#endif
+
+
+//
+// Implementation
+//
+
+#if defined(RTC)
+
+double Timer::seconds() {
+	return (double) read_rtc() * time_factor;
+}
+
+int64 Timer::ticks() {
+	// See pg. 406 of the AMD x86-64 Architecture
+	// Programmer's Manual, Volume 2, System Programming
+	unsigned int eax = 0, edx = 0;
+
+	__asm__ __volatile__(
+			"rdtsc ;"
+			"movl %%eax,%0;"
+			"movl %%edx,%1;"
+			""
+			: "=r"(eax), "=r"(edx)
+			:
+			: "%eax", "%edx"
+	);
+
+	return ((int64) edx << 32) | (int64) eax;
+}
+
+static int64 read_rtc() {
+	// See pg. 406 of the AMD x86-64 Architecture
+	// Programmer's Manual, Volume 2, System Programming
+	unsigned int eax = 0, edx = 0;
+
+	__asm__ __volatile__(
+			"rdtsc ;"
+			"movl %%eax,%0;"
+			"movl %%edx,%1;"
+			""
+			: "=r"(eax), "=r"(edx)
+			:
+			: "%eax", "%edx"
+	);
+
+	return ((int64) edx << 32) | (int64) eax;
+}
+
+void Timer::calibrate() {
+	Timer::calibrate(1000);
+}
+
+void Timer::calibrate(int n) {
+	wall_ticks = n;
+
+	double wall_start, wall_finish, t;
+	t = wall_seconds();
+	while (t == (wall_start = wall_seconds())) {
+		;
+	}
+	int64 rtc_start = read_rtc();
+	for (int i = 0; i < wall_ticks; i++) {
+		t = wall_seconds();
+		while (t == (wall_finish = wall_seconds())) {
+			;
+		}
+	}
+	int64 rtc_finish = read_rtc();
+
+	wall_elapsed = wall_finish - wall_start;
+	rtc_elapsed = rtc_finish - rtc_start;
+	time_factor = wall_elapsed / (double) rtc_elapsed;
+}
+
+static double wall_seconds() {
+	struct timeval t;
+	gettimeofday(&t, NULL);
+
+	return (double) t.tv_sec + (double) t.tv_usec * 1E-6;
+}
+
+#else
+
+double
+Timer::seconds()
+{
+	struct timeval t;
+	gettimeofday(&t, NULL);
+
+	return (double) t.tv_sec + (double) t.tv_usec * 1E-6;
+}
+
+int64
+Timer::ticks()
+{
+	struct timeval t;
+	gettimeofday(&t, NULL);
+
+	return 1000000 * (int64) t.tv_sec + (int64) t.tv_usec;
+}
+
+void
+Timer::calibrate()
+{
+}
+
+void
+Timer::calibrate(int n)
+{
+}
+
+#endif
+
+static double min(double v1, double v2) {
+	if (v2 < v1)
+		return v2;
+	return v1;
+}
+
+double Timer::resolution() {
+	double a, b, c = 1E9;
+	for (int i = 0; i < 10; i++) {
+		a = Timer::seconds();
+		while (a == (b = Timer::seconds()))
+			;
+		a = Timer::seconds();
+		while (a == (b = Timer::seconds()))
+			;
+		c = min(b - a, c);
+	}
+
+	return c;
+}