Create libsampler as V8 sampler library.

src/libsampler/v8-sampler.h

-// Copyright 2013 the V8 project authors. All rights reserved.
+// Copyright 2016 the V8 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.
 
-#ifndef V8_PROFILER_SAMPLER_H_
-#define V8_PROFILER_SAMPLER_H_
+#ifndef V8_LIBSAMPLER_SAMPLER_H_
+#define V8_LIBSAMPLER_SAMPLER_H_
 
 #include "include/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/macros.h"
 
 namespace v8 {
-namespace internal {
-
-class Isolate;
-struct TickSample;
+namespace sampler {
 
 // ----------------------------------------------------------------------------
 // Sampler
 //
 // A sampler periodically samples the state of the VM and optionally
 // (if used for profiling) the program counter and stack pointer for
 // the thread that created it.
 
 class Sampler {
  public:
+  static const int kMaxFramesCountLog2 = 8;
+  static const unsigned kMaxFramesCount = (1u << kMaxFramesCountLog2) - 1;
+
   // Initializes the Sampler support. Called once at VM startup.
   static void SetUp();
   static void TearDown();
 
   // Initialize sampler.
-  Sampler(Isolate* isolate, int interval);
+  explicit Sampler(Isolate* isolate);
   virtual ~Sampler();
 
   Isolate* isolate() const { return isolate_; }
-  int interval() const { return interval_; }
 
   // Performs stack sampling.
-  void SampleStack(const v8::RegisterState& regs);
+  // Clients should override this method in order to do something on samples,
+  // for example buffer samples in a queue.
+  virtual void SampleStack(const v8::RegisterState& regs) = 0;
 
   // Start and stop sampler.
   void Start();
   void Stop();
 
   // Whether the sampling thread should use this Sampler for CPU profiling?
   bool IsProfiling() const {
     return base::NoBarrier_Load(&profiling_) > 0 &&
         !base::NoBarrier_Load(&has_processing_thread_);
   }
   void IncreaseProfilingDepth();
   void DecreaseProfilingDepth();
 
   // Whether the sampler is running (that is, consumes resources).
   bool IsActive() const { return base::NoBarrier_Load(&active_); }
 
   // CpuProfiler collects samples by calling DoSample directly
   // without calling Start. To keep it working, we register the sampler
   // with the CpuProfiler.
   bool IsRegistered() const { return base::NoBarrier_Load(&registered_); }
 
   void DoSample();
-  // If true next sample must be initiated on the profiler event processor
-  // thread right after latest sample is processed.
+
   void SetHasProcessingThread(bool value) {
     base::NoBarrier_Store(&has_processing_thread_, value);
   }
 
   // Used in tests to make sure that stack sampling is performed.
   unsigned js_sample_count() const { return js_sample_count_; }
   unsigned external_sample_count() const { return external_sample_count_; }
   void StartCountingSamples() {
     js_sample_count_ = 0;
     external_sample_count_ = 0;
     is_counting_samples_ = true;
   }
 
   class PlatformData;
   PlatformData* platform_data() const { return data_; }
 
  protected:
-  // This method is called for each sampling period with the current
-  // program counter.
-  virtual void Tick(TickSample* sample) = 0;
+  // Counts stack samples taken in various VM states.
+  bool is_counting_samples_;
+  unsigned js_sample_count_;
+  unsigned external_sample_count_;
 
  private:
   void SetActive(bool value) { base::NoBarrier_Store(&active_, value); }
-
   void SetRegistered(bool value) { base::NoBarrier_Store(&registered_, value); }
 
   Isolate* isolate_;
-  const int interval_;
   base::Atomic32 profiling_;
   base::Atomic32 has_processing_thread_;
   base::Atomic32 active_;
   base::Atomic32 registered_;
   PlatformData* data_;  // Platform specific data.
-  // Counts stack samples taken in various VM states.
-  bool is_counting_samples_;
-  unsigned js_sample_count_;
-  unsigned external_sample_count_;
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
-}  // namespace internal
+}  // namespace sampler
 }  // namespace v8
 
-#endif  // V8_PROFILER_SAMPLER_H_
+#endif  // V8_LIBSAMPLER_SAMPLER_H_