timer: use monotonic clock if available

Makefile.am

@@ -227,6 +227,7 @@ src_mpd_SOURCES = \
 	$(OUTPUT_API_SRC) \
 	$(MIXER_API_SRC) \
 	src/glib_socket.h \
+	src/clock.c src/clock.h \
 	src/notify.c \
 	src/audio_config.c src/audio_config.h \
 	src/audio_check.c \
@@ -1069,7 +1070,7 @@ test_dump_playlist_SOURCES = test/dump_playlist.c \
 	src/audio_check.c src/pcm_buffer.c \
 	src/text_input_stream.c src/fifo_buffer.c \
 	src/cue/cue_parser.c src/cue/cue_parser.h \
-	src/timer.c \
+	src/timer.c src/clock.c \
 	src/fd_util.c
 
 if HAVE_FLAC
@@ -1096,7 +1097,7 @@ test_run_decoder_SOURCES = test/run_decoder.c \
 	src/fd_util.c \
 	src/audio_check.c \
 	src/audio_format.c \
-	src/timer.c \
+	src/timer.c src/clock.c \
 	$(ARCHIVE_SRC) \
 	$(INPUT_SRC) \
 	$(TAG_SRC) \
@@ -1118,7 +1119,7 @@ test_read_tags_SOURCES = test/read_tags.c \
 	src/uri.c \
 	src/fd_util.c \
 	src/audio_check.c \
-	src/timer.c \
+	src/timer.c src/clock.c \
 	$(DECODER_SRC)
 
 if HAVE_ID3TAG
@@ -1240,7 +1241,7 @@ test_run_output_SOURCES = test/run_output.c \
 	src/audio_check.c \
 	src/audio_format.c \
 	src/audio_parser.c \
-	src/timer.c \
+	src/timer.c src/clock.c \
 	src/tag.c src/tag_pool.c \
 	src/fifo_buffer.c src/growing_fifo.c \
 	src/page.c \

NEWS

 ver 0.17.2 (2012/??/??)
 * protocol:
   - fix crash in local file check
+* output:
+  - httpd: use monotonic clock, avoid hiccups after system clock adjustment
 * mapper: fix non-UTF8 music directory name
 
 

src/clock.c

+/*
+ * Copyright (C) 2003-2012 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "clock.h"
+
+#ifdef WIN32
+#include <windows.h>
+#elif defined(__APPLE__)
+#include <mach/mach_time.h>
+#else
+#include <time.h>
+#endif
+
+unsigned
+monotonic_clock_ms(void)
+{
+#ifdef WIN32
+	return GetTickCount();
+#elif defined(__APPLE__) /* OS X does not define CLOCK_MONOTONIC */
+	static mach_timebase_info_data_t base;
+	if (base.denom == 0)
+		(void)mach_timebase_info(&base);
+
+	return (unsigned)((mach_absolute_time() * base.numer)
+			  / (1000000 * base.denom));
+#elif defined(CLOCK_MONOTONIC)
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
+#else
+	/* we have no monotonic clock, fall back to gettimeofday() */
+	struct timeval tv;
+	gettimeofday(&tv, 0);
+	return tv.tv_sec * 1000 + tv.tv_usec / 1000;
+#endif
+}
+
+uint64_t
+monotonic_clock_us(void)
+{
+#ifdef WIN32
+	LARGE_INTEGER l_value, l_frequency;
+
+	if (!QueryPerformanceCounter(&l_value) ||
+	    !QueryPerformanceFrequency(&l_frequency))
+		return 0;
+
+	uint64_t value = l_value.QuadPart;
+	uint64_t frequency = l_frequency.QuadPart;
+
+	if (frequency > 1000000) {
+		value *= 10000;
+		value /= frequency / 100;
+	} else if (frequency < 1000000) {
+		value *= 10000;
+		value /= frequency;
+		value *= 100;
+	}
+
+	return value;
+#elif defined(__APPLE__) /* OS X does not define CLOCK_MONOTONIC */
+	static mach_timebase_info_data_t base;
+	if (base.denom == 0)
+		(void)mach_timebase_info(&base);
+
+	return ((uint64_t)mach_absolute_time() * (uint64_t)base.numer)
+		/ (1000 * (uint64_t)base.denom);
+#elif defined(CLOCK_MONOTONIC)
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return (uint64_t)ts.tv_sec * 1000000 + (uint64_t)(ts.tv_nsec / 1000);
+#else
+	/* we have no monotonic clock, fall back to gettimeofday() */
+	struct timeval tv;
+	gettimeofday(&tv, 0);
+	return (uint64_t)tv.tv_sec * 1000 + (uint64_t)(tv.tv_usec) / 1000(;
+#endif
+}
+

src/clock.h

+/*
+ * Copyright (C) 2003-2012 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_CLOCK_H
+#define MPD_CLOCK_H
+
+#include <glib.h>
+
+#include <stdint.h>
+
+/**
+ * Returns the value of a monotonic clock in milliseconds.
+ */
+G_GNUC_PURE
+unsigned
+monotonic_clock_ms(void);
+
+/**
+ * Returns the value of a monotonic clock in microseconds.
+ */
+G_GNUC_PURE
+uint64_t
+monotonic_clock_us(void);
+
+#endif

src/timer.c

@@ -20,23 +20,14 @@
 #include "config.h"
 #include "timer.h"
 #include "audio_format.h"
+#include "clock.h"
 
 #include <glib.h>
 
 #include <assert.h>
 #include <limits.h>
-#include <sys/time.h>
 #include <stddef.h>
 
-static uint64_t now(void)
-{
-	struct timeval tv;
-
-	gettimeofday(&tv, NULL);
-
-	return ((uint64_t)tv.tv_sec * 1000000) + tv.tv_usec;
-}
-
 struct timer *timer_new(const struct audio_format *af)
 {
 	struct timer *timer = g_new(struct timer, 1);
@@ -54,7 +45,7 @@ void timer_free(struct timer *timer)
 
 void timer_start(struct timer *timer)
 {
-	timer->time = now();
+	timer->time = monotonic_clock_us();
 	timer->started = 1;
 }
 
@@ -74,7 +65,7 @@ void timer_add(struct timer *timer, int size)
 unsigned
 timer_delay(const struct timer *timer)
 {
-	int64_t delay = (int64_t)(timer->time - now()) / 1000;
+	int64_t delay = (int64_t)(timer->time - monotonic_clock_us()) / 1000;
 	if (delay < 0)
 		return 0;
 
@@ -90,7 +81,7 @@ void timer_sync(struct timer *timer)
 
 	assert(timer->started);
 
-	sleep_duration = timer->time - now();
+	sleep_duration = timer->time - monotonic_clock_us();
 	if (sleep_duration > 0)
 		g_usleep(sleep_duration);
 }