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SeqNumUnwrapper::Unwrap now returns int64_t instead of uint64_t.

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Bug: webrtc:10263
Change-Id: Idaeae6be01bd4eba0691226c958d70e114161ffd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/127295
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Johannes Kron <kron@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27129}
This commit is contained in:
philipel
2019-03-14 10:52:37 +01:00
committed by Commit Bot
parent e8efbbd61b
commit b0f968a761
9 changed files with 409 additions and 448 deletions
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43
rtc_base/numerics/sequence_number_util.h
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@ -81,46 +81,35 @@ struct DescendingSeqNumComp {
bool operator()(T a, T b) const { return AheadOf<T, M>(b, a); }
};
// A sequencer number unwrapper where the start value of the unwrapped sequence
// can be set. The unwrapped value is not allowed to wrap.
// A sequence number unwrapper where the first unwrapped value equals the
// first value being unwrapped.
template <typename T, T M = 0>
class SeqNumUnwrapper {
// Use '<' instead of rtc::SafeLt to avoid crbug.com/753488
static_assert(
std::is_unsigned<T>::value &&
std::numeric_limits<T>::max() < std::numeric_limits<uint64_t>::max(),
"Type unwrapped must be an unsigned integer smaller than uint64_t.");
std::numeric_limits<T>::max() < std::numeric_limits<int64_t>::max(),
"Type unwrapped must be an unsigned integer smaller than int64_t.");
public:
// We want a default value that is close to 2^62 for a two reasons. Firstly,
// we can unwrap wrapping numbers in either direction, and secondly, the
// unwrapped numbers can be stored in either int64_t or uint64_t. We also want
// the default value to be human readable, which makes a power of 10 suitable.
static constexpr uint64_t kDefaultStartValue = 1000000000000000000UL;
SeqNumUnwrapper() : last_unwrapped_(kDefaultStartValue) {}
explicit SeqNumUnwrapper(uint64_t start_at) : last_unwrapped_(start_at) {}
uint64_t Unwrap(T value) {
if (!last_value_)
last_value_.emplace(value);
uint64_t unwrapped = 0;
if (AheadOrAt<T, M>(value, *last_value_)) {
unwrapped = last_unwrapped_ + ForwardDiff<T, M>(*last_value_, value);
RTC_CHECK_GE(unwrapped, last_unwrapped_);
int64_t Unwrap(T value) {
if (!last_value_) {
last_unwrapped_ = {value};
} else {
unwrapped = last_unwrapped_ - ReverseDiff<T, M>(*last_value_, value);
RTC_CHECK_LT(unwrapped, last_unwrapped_);
last_unwrapped_ += ForwardDiff<T, M>(*last_value_, value);
if (!AheadOrAt<T, M>(value, *last_value_)) {
constexpr int64_t kBackwardAdjustment =
M == 0 ? int64_t{std::numeric_limits<T>::max()} + 1 : M;
last_unwrapped_ -= kBackwardAdjustment;
}
}
*last_value_ = value;
last_unwrapped_ = unwrapped;
last_value_ = value;
return last_unwrapped_;
}
private:
uint64_t last_unwrapped_;
int64_t last_unwrapped_ = 0;
absl::optional<T> last_value_;
};