[fix] fix crash due to rtp extension

src/qos/ntp_time_util.cc

@@ -0,0 +1,59 @@
+/*
+ *  Copyright (c) 2016 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.
+ */
+
+#include "ntp_time_util.h"
+
+#include <algorithm>
+#include <cstdint>
+
+#include "api/units/time_delta.h"
+#include "rtc_base/numerics/divide_round.h"
+#include "rtc_base/time_utils.h"
+
+namespace webrtc {
+
+uint32_t SaturatedToCompactNtp(TimeDelta delta) {
+  constexpr uint32_t kMaxCompactNtp = 0xFFFFFFFF;
+  constexpr int kCompactNtpInSecond = 0x10000;
+  if (delta <= TimeDelta::Zero()) return 0;
+  if (delta.us() >=
+      kMaxCompactNtp * rtc::kNumMicrosecsPerSec / kCompactNtpInSecond)
+    return kMaxCompactNtp;
+  // To convert to compact ntp need to divide by 1e6 to get seconds,
+  // then multiply by 0x10000 to get the final result.
+  // To avoid float operations, multiplication and division swapped.
+  return DivideRoundToNearest(delta.us() * kCompactNtpInSecond,
+                              rtc::kNumMicrosecsPerSec);
+}
+
+TimeDelta CompactNtpIntervalToTimeDelta(uint32_t compact_ntp_interval) {
+  // Convert to 64bit value to avoid multiplication overflow.
+  int64_t value = int64_t{compact_ntp_interval};
+  if (compact_ntp_interval > 0x8000'0000) {
+    value -= (int64_t{1} << 32);
+  }
+  // To convert to TimeDelta need to divide by 2^16 to get seconds,
+  // then multiply by 1'000'000 to get microseconds. To avoid float operations,
+  // multiplication and division are swapped.
+  int64_t us = DivideRoundToNearest(value * rtc::kNumMicrosecsPerSec, 1 << 16);
+  return TimeDelta::Micros(us);
+}
+
+TimeDelta CompactNtpRttToTimeDelta(uint32_t compact_ntp_interval) {
+  static constexpr TimeDelta kMinRtt = TimeDelta::Millis(1);
+  // Interval to convert expected to be positive, e.g. RTT or delay.
+  // Because interval can be derived from non-monotonic ntp clock,
+  // it might become negative that is indistinguishable from very large values.
+  // Since very large RTT/delay is less likely than non-monotonic ntp clock,
+  // such value is considered negative and converted to minimum value of 1ms.
+  // Small RTT value is considered too good to be true and increased to 1ms.
+  return std::max(CompactNtpIntervalToTimeDelta(compact_ntp_interval), kMinRtt);
+}
+}  // namespace webrtc