Introduce TimeWindowedBuffer (facebook#54679)

Summary:
Pull Request resolved: facebook#54679

# Changelog: [Internal]

Adding a data structure that could be configured to preserve entries that are inside of a specified time window.

At the same time, this data structure could be used as a simple buffer, if no arguments were specified during constructing.

This follows the approach that was added to `PerformanceTracer`, but it doesn't use pointers to avoid dealing with updates during copies or moves.

Reviewed By: sbuggay

Differential Revision: D87776299

fbshipit-source-id: d20bf6dd08af7971aaf34ffc11ec5993b8edaf4b

Author: hoxyq

packages/react-native/ReactCommon/jsinspector-modern/tracing/TimeWindowedBuffer.h

@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <algorithm>
+#include <functional>
+#include <optional>
+#include <vector>
+
+#include <react/timing/primitives.h>
+
+namespace facebook::react::jsinspector_modern::tracing {
+
+/**
+ * The currentBufferStartTime_ is initialized once first element is pushed.
+ */
+constexpr HighResTimeStamp kCurrentBufferStartTimeUninitialized = HighResTimeStamp::min();
+
+template <typename T>
+class TimeWindowedBuffer {
+ public:
+  using TimestampAccessor = std::function<HighResTimeStamp(const T &)>;
+
+  TimeWindowedBuffer() : timestampAccessor_(std::nullopt), windowSize_(std::nullopt) {}
+
+  TimeWindowedBuffer(TimestampAccessor timestampAccessor, HighResDuration windowSize)
+      : timestampAccessor_(std::move(timestampAccessor)), windowSize_(windowSize)
+  {
+  }
+
+  void push(const T &element)
+  {
+    if (timestampAccessor_) {
+      auto timestamp = (*timestampAccessor_)(element);
+      enqueueElement(element, timestamp);
+    } else {
+      enqueueElement(element, HighResTimeStamp::now());
+    }
+  }
+
+  void push(T &&element)
+  {
+    if (timestampAccessor_) {
+      auto timestamp = (*timestampAccessor_)(element);
+      enqueueElement(std::move(element), timestamp);
+    } else {
+      enqueueElement(std::move(element), HighResTimeStamp::now());
+    }
+  }
+
+  void clear()
+  {
+    primaryBuffer_.clear();
+    alternativeBuffer_.clear();
+    currentBufferIndex_ = BufferIndex::Primary;
+    currentBufferStartTime_ = kCurrentBufferStartTimeUninitialized;
+  }
+
+  /**
+   * Forces immediate removal of elements that are outside the time window.
+   * The right boundary of the window is the reference timestamp passed as an argument.
+   */
+  std::vector<T> pruneExpiredAndExtract(HighResTimeStamp windowRightBoundary = HighResTimeStamp::now())
+  {
+    std::vector<T> result;
+
+    for (auto &wrappedElement : getPreviousBuffer()) {
+      if (isInsideTimeWindow(wrappedElement, windowRightBoundary)) {
+        result.push_back(std::move(wrappedElement.element));
+      }
+    }
+
+    for (auto &wrappedElement : getCurrentBuffer()) {
+      if (isInsideTimeWindow(wrappedElement, windowRightBoundary)) {
+        result.push_back(std::move(wrappedElement.element));
+      }
+    }
+
+    clear();
+    return result;
+  }
+
+ private:
+  enum class BufferIndex { Primary, Alternative };
+
+  struct TimestampedElement {
+    T element;
+    HighResTimeStamp timestamp;
+  };
+
+  std::vector<TimestampedElement> &getCurrentBuffer()
+  {
+    return currentBufferIndex_ == BufferIndex::Primary ? primaryBuffer_ : alternativeBuffer_;
+  }
+
+  std::vector<TimestampedElement> &getPreviousBuffer()
+  {
+    return currentBufferIndex_ == BufferIndex::Primary ? alternativeBuffer_ : primaryBuffer_;
+  }
+
+  void enqueueElement(const T &element, HighResTimeStamp timestamp)
+  {
+    if (windowSize_) {
+      if (currentBufferStartTime_ == kCurrentBufferStartTimeUninitialized) {
+        currentBufferStartTime_ = timestamp;
+      } else if (timestamp > currentBufferStartTime_ + *windowSize_) {
+        // We moved past the current buffer. We need to switch the other buffer as current.
+        currentBufferIndex_ =
+            currentBufferIndex_ == BufferIndex::Primary ? BufferIndex::Alternative : BufferIndex::Primary;
+        getCurrentBuffer().clear();
+        currentBufferStartTime_ = timestamp;
+      }
+    }
+
+    getCurrentBuffer().push_back({element, timestamp});
+  }
+
+  void enqueueElement(T &&element, HighResTimeStamp timestamp)
+  {
+    if (windowSize_) {
+      if (currentBufferStartTime_ == kCurrentBufferStartTimeUninitialized) {
+        currentBufferStartTime_ = timestamp;
+      } else if (timestamp > currentBufferStartTime_ + *windowSize_) {
+        // We moved past the current buffer. We need to switch the other buffer as current.
+        currentBufferIndex_ =
+            currentBufferIndex_ == BufferIndex::Primary ? BufferIndex::Alternative : BufferIndex::Primary;
+        getCurrentBuffer().clear();
+        currentBufferStartTime_ = timestamp;
+      }
+    }
+
+    getCurrentBuffer().push_back({std::move(element), timestamp});
+  }
+
+  bool isInsideTimeWindow(const TimestampedElement &element, HighResTimeStamp windowRightBoundary) const
+  {
+    if (!windowSize_) {
+      return true;
+    }
+
+    return element.timestamp >= windowRightBoundary - *windowSize_ && element.timestamp <= windowRightBoundary;
+  }
+
+  std::optional<TimestampAccessor> timestampAccessor_;
+  std::optional<HighResDuration> windowSize_;
+
+  std::vector<TimestampedElement> primaryBuffer_;
+  std::vector<TimestampedElement> alternativeBuffer_;
+  BufferIndex currentBufferIndex_ = BufferIndex::Primary;
+  HighResTimeStamp currentBufferStartTime_{kCurrentBufferStartTimeUninitialized};
+};
+
+} // namespace facebook::react::jsinspector_modern::tracing