[rtp_rtcp] time helper functions

webrtc/modules/rtp_rtcp/source/time_util.h

Index: webrtc/modules/rtp_rtcp/source/time_util.h
diff --git a/webrtc/modules/rtp_rtcp/source/time_util.h b/webrtc/modules/rtp_rtcp/source/time_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..5b544ddf9abc0b0cc98fff993ebb4ba2010306e2
--- /dev/null
+++ b/webrtc/modules/rtp_rtcp/source/time_util.h
@@ -0,0 +1,48 @@
+/*
+ *  Copyright (c) 2015 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_MODULES_RTP_RTCP_SOURCE_TIME_UTIL_H_
+#define WEBRTC_MODULES_RTP_RTCP_SOURCE_TIME_UTIL_H_
+
+#include "webrtc/base/basictypes.h"
+#include "webrtc/system_wrappers/include/ntp_time.h"
+
+namespace webrtc {
+
+// Converts NTP timestamp to RTP timestamp.
+inline uint32_t NtpToRtp(NtpTime ntp, uint32_t freq) {
+  uint32_t tmp = (static_cast<uint64_t>(ntp.fractions()) * freq) >> 32;
+  return ntp.seconds() * freq + tmp;
+}
+// Return the current RTP timestamp from the NTP timestamp
+// returned by the specified clock.
+inline uint32_t CurrentRtp(const Clock& clock, uint32_t freq) {
+  return NtpToRtp(NtpTime(clock), freq);
+}
+
+// Helper function for compact ntp representation:
+// RFC 3550, Section 4. Time Format.
+// Wallclock time is represented using the timestamp format of
+// the Network Time Protocol (NTP).
+// ...
+// In some fields where a more compact representation is
+// appropriate, only the middle 32 bits are used; that is, the low 16
+// bits of the integer part and the high 16 bits of the fractional part.
+inline uint32_t CompactNtp(NtpTime ntp) {
+  return (ntp.seconds() << 16) | (ntp.fractions() >> 16);
+}
+// Converts interval between compact ntp timestamps to milliseconds.
+// This interval can be upto ~18.2 hours (2^16 seconds).
+inline uint32_t CompactNtpIntervalToMs(uint32_t compact_ntp_interval) {
+  return static_cast<uint64_t>(compact_ntp_interval) * 1000 / (1 << 16);
+}
+
+}  // namespace webrtc
+#endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_TIME_UTIL_H_