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TMessagesProj/jni/voip/webrtc/base/profiler/sample_metadata.h

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+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_PROFILER_SAMPLE_METADATA_H_
+#define BASE_PROFILER_SAMPLE_METADATA_H_
+
+#include "base/optional.h"
+#include "base/profiler/metadata_recorder.h"
+#include "base/strings/string_piece.h"
+
+// -----------------------------------------------------------------------------
+// Usage documentation
+// -----------------------------------------------------------------------------
+//
+// Overview:
+// These functions provide a means to control the metadata attached to samples
+// collected by the stack sampling profiler. Metadata state is shared between
+// all threads within a process.
+//
+// Any samples collected by the sampling profiler will include the active
+// metadata. This enables us to later analyze targeted subsets of samples
+// (e.g. those collected during paint or layout).
+//
+// For example:
+//
+//   void DidStartLoad() {
+//     base::SetSampleMetadata("Renderer.IsLoading", 1);
+//   }
+//
+//   void DidFinishLoad() {
+//     base::RemoveSampleMetadata("Renderer.IsLoading");
+//   }
+//
+// Alternatively, ScopedSampleMetadata can be used to ensure that the metadata
+// is removed correctly.
+//
+// For example:
+//
+//   void DoExpensiveWork() {
+//     base::ScopedSampleMetadata metadata("xyz", 1);
+//     if (...) {
+//       ...
+//       if (...) {
+//         ...
+//         return;
+//       }
+//     }
+//     ...
+//   }
+
+namespace base {
+
+class BASE_EXPORT ScopedSampleMetadata {
+ public:
+  // Set the metadata value associated with |name|.
+  ScopedSampleMetadata(StringPiece name, int64_t value);
+
+  // Set the metadata value associated with the pair (|name|, |key|). This
+  // constructor allows the metadata to be associated with an additional
+  // user-defined key. One might supply a key based on the frame id, for
+  // example, to distinguish execution in service of scrolling between different
+  // frames. Prefer the previous constructor if no user-defined metadata is
+  // required. Note: values specified for a name and key are stored separately
+  // from values specified with only a name.
+  ScopedSampleMetadata(StringPiece name, int64_t key, int64_t value);
+
+  ScopedSampleMetadata(const ScopedSampleMetadata&) = delete;
+  ~ScopedSampleMetadata();
+
+  ScopedSampleMetadata& operator=(const ScopedSampleMetadata&) = delete;
+
+ private:
+  const uint64_t name_hash_;
+  Optional<int64_t> key_;
+};
+
+// Set the metadata value associated with |name| in the process-global stack
+// sampling profiler metadata, overwriting any previous value set for that
+// |name|.
+BASE_EXPORT void SetSampleMetadata(StringPiece name, int64_t value);
+
+// Set the metadata value associated with the pair (|name|, |key|) in the
+// process-global stack sampling profiler metadata, overwriting any previous
+// value set for that (|name|, |key|) pair. This constructor allows the metadata
+// to be associated with an additional user-defined key. One might supply a key
+// based on the frame id, for example, to distinguish execution in service of
+// scrolling between different frames. Prefer the previous function if no
+// user-defined metadata is required. Note: values specified for a name and key
+// are stored separately from values specified with only a name.
+BASE_EXPORT void SetSampleMetadata(StringPiece name,
+                                   int64_t key,
+                                   int64_t value);
+
+// Removes the metadata item with the specified name from the process-global
+// stack sampling profiler metadata.
+//
+// If such an item doesn't exist, this has no effect.
+BASE_EXPORT void RemoveSampleMetadata(StringPiece name);
+
+// Removes the metadata item with the specified (|name|, |key|) pair from the
+// process-global stack sampling profiler metadata. This function does not alter
+// values set with the name |name| but no key.
+//
+// If such an item doesn't exist, this has no effect.
+BASE_EXPORT void RemoveSampleMetadata(StringPiece name, int64_t key);
+
+// Applies the specified metadata to samples already recorded between
+// |period_start| and |period_end| in all thread's active profiles, subject to
+// the condition that the profile fully encompasses the period and the profile
+// has not already completed. The condition ensures that the metadata is applied
+// only if all execution during its scope was seen in the profile. This avoids
+// biasng the samples towards the 'middle' of the execution seen during the
+// metadata scope (i.e. because the start or end of execution was missed), at
+// the cost of missing execution that are longer than the profiling period, or
+// extend before or after it. |period_end| must be <= TimeTicks::Now().
+BASE_EXPORT void ApplyMetadataToPastSamples(TimeTicks period_start,
+                                            TimeTicks period_end,
+                                            StringPiece name,
+                                            int64_t value);
+BASE_EXPORT void ApplyMetadataToPastSamples(TimeTicks period_start,
+                                            TimeTicks period_end,
+                                            StringPiece name,
+                                            int64_t key,
+                                            int64_t value);
+
+// Returns the process-global metadata recorder instance used for tracking
+// sampling profiler metadata.
+//
+// This function should not be called by non-profiler related code.
+BASE_EXPORT MetadataRecorder* GetSampleMetadataRecorder();
+
+}  // namespace base
+
+#endif  // BASE_PROFILER_SAMPLE_METADATA_H_