Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/timeutils.h

@@ -0,0 +1,85 @@
+/*
+ *  Copyright 2005 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_TIMEUTILS_H_
+#define WEBRTC_BASE_TIMEUTILS_H_
+
+#include <time.h>
+
+#include "webrtc/base/basictypes.h"
+
+namespace rtc {
+
+static const int64 kNumMillisecsPerSec = INT64_C(1000);
+static const int64 kNumMicrosecsPerSec = INT64_C(1000000);
+static const int64 kNumNanosecsPerSec = INT64_C(1000000000);
+
+static const int64 kNumMicrosecsPerMillisec = kNumMicrosecsPerSec /
+    kNumMillisecsPerSec;
+static const int64 kNumNanosecsPerMillisec =  kNumNanosecsPerSec /
+    kNumMillisecsPerSec;
+static const int64 kNumNanosecsPerMicrosec =  kNumNanosecsPerSec /
+    kNumMicrosecsPerSec;
+
+// January 1970, in NTP milliseconds.
+static const int64 kJan1970AsNtpMillisecs = INT64_C(2208988800000);
+
+typedef uint32 TimeStamp;
+
+// Returns the current time in milliseconds.
+uint32 Time();
+// Returns the current time in microseconds.
+uint64 TimeMicros();
+// Returns the current time in nanoseconds.
+uint64 TimeNanos();
+
+// Stores current time in *tm and microseconds in *microseconds.
+void CurrentTmTime(struct tm *tm, int *microseconds);
+
+// Returns a future timestamp, 'elapsed' milliseconds from now.
+uint32 TimeAfter(int32 elapsed);
+
+// Comparisons between time values, which can wrap around.
+bool TimeIsBetween(uint32 earlier, uint32 middle, uint32 later);  // Inclusive
+bool TimeIsLaterOrEqual(uint32 earlier, uint32 later);  // Inclusive
+bool TimeIsLater(uint32 earlier, uint32 later);  // Exclusive
+
+// Returns the later of two timestamps.
+inline uint32 TimeMax(uint32 ts1, uint32 ts2) {
+  return TimeIsLaterOrEqual(ts1, ts2) ? ts2 : ts1;
+}
+
+// Returns the earlier of two timestamps.
+inline uint32 TimeMin(uint32 ts1, uint32 ts2) {
+  return TimeIsLaterOrEqual(ts1, ts2) ? ts1 : ts2;
+}
+
+// Number of milliseconds that would elapse between 'earlier' and 'later'
+// timestamps.  The value is negative if 'later' occurs before 'earlier'.
+int32 TimeDiff(uint32 later, uint32 earlier);
+
+// The number of milliseconds that have elapsed since 'earlier'.
+inline int32 TimeSince(uint32 earlier) {
+  return TimeDiff(Time(), earlier);
+}
+
+// The number of milliseconds that will elapse between now and 'later'.
+inline int32 TimeUntil(uint32 later) {
+  return TimeDiff(later, Time());
+}
+
+// Converts a unix timestamp in nanoseconds to an NTP timestamp in ms.
+inline int64 UnixTimestampNanosecsToNtpMillisecs(int64 unix_ts_ns) {
+  return unix_ts_ns / kNumNanosecsPerMillisec + kJan1970AsNtpMillisecs;
+}
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_TIMEUTILS_H_