Initial GetSample implementation.

test/cctest/test-sampler-api.cc

+// Copyright 2014 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.
+//
+// Tests the public sampling API in include/v8.h
+
+#include <string>
+
+#include "include/v8.h"
+
+#include "src/v8.h"
+
+#include "src/base/platform/platform.h"
+
+#include "test/cctest/cctest.h"
+
+using v8::Local;
+
+namespace {
+  // Sampler thread waits on this semaphore.
+  v8::base::Semaphore* SamplerSemaphore = new v8::base::Semaphore(0);

[Benedikt Meurer, 2014/08/29 04:23:49]

Nit: Variable naming, SamplerSemaphore -> sampler_semaphore.

+
+  // V8 thread (the JavaScript code) waits on this semaphore.
+  v8::base::Semaphore* V8Semaphore = new v8::base::Semaphore(0);

[Benedikt Meurer, 2014/08/29 04:23:49]

Nit: Variable naming. 

+
+  // The JavaScript calls this function when on full stack depth.
+  void SignalAndWaitForSampler(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
+    // Tell the sampler that it can take a sample now.
+    SamplerSemaphore->Signal();
+
+    // Wait for the sampler to finish collecting a sample.
+    V8Semaphore->Wait();
+  }
+}
+
+
+// A thread which collects samples from v8.
+class V8_FINAL SamplerThread : public v8::base::Thread {
+ public:
+  explicit SamplerThread(v8::Isolate* isolate)
+    : Thread(v8::base::Thread::Options("sampler-api-tester")),
+      isolate_(isolate) {
+  }
+
+  virtual ~SamplerThread() {}
+
+  virtual void Run() {
+    SamplerSemaphore->Wait();  // Wait for JS to reach full stack depth.
+    isolate_->GetSample(&sample);
+    V8Semaphore->Signal();     // Tell JS that sample collection is done.
+  }
+
+  v8::Sample sample;
+
+ private:
+  v8::Isolate* isolate_;
+};
+
+
+// A JavaScript function which takes stack depth
+// (minimum value 2) as an argument.
+// When at the bottom of the recursion,
+// the JavaScript code calls into C++ test code,
+// waiting for the sampler to take a sample.
+static const char* sampler_api_test_function = "function func(depth) {"
+"  if (depth == 2) SignalAndWaitForSampler();"
+"  else return func(depth - 1);"
+"}";
+
+
+// TODO(gholap): Right now, we are just checking whether GetSample
+//               gets samples and whether the stack depth is reasonable.
+//               After implementing code event listener API, add tests
+//               to further verify the correctness of collected samples.
+TEST(StackDepthIsConsistent) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope scope(isolate);
+  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New(isolate);
+  global->Set(
+    v8::String::NewFromUtf8(isolate, "SignalAndWaitForSampler"),
+    v8::FunctionTemplate::New(isolate, SignalAndWaitForSampler));
+
+  LocalContext env(isolate, NULL, global);
+  std::string source(sampler_api_test_function);
+  source.append("func(8);");
+  Local<v8::Script> script = v8::Script::Compile(
+    v8::String::NewFromUtf8(isolate, source.c_str()));
+  SamplerThread sampler(isolate);
+
+  sampler.Start();
+  script->Run();
+  sampler.Join();
+
+  CHECK_EQ(8, sampler.sample.frames_count);
+}
+
+
+TEST(StackDepthDoesNotExceedMaxValue) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope scope(isolate);
+  v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New(isolate);
+  global->Set(
+    v8::String::NewFromUtf8(isolate, "SignalAndWaitForSampler"),
+    v8::FunctionTemplate::New(isolate, SignalAndWaitForSampler));
+
+  LocalContext env(isolate, NULL, global);
+  std::string source(sampler_api_test_function);
+  source.append("func(300);");
+  Local<v8::Script> script = v8::Script::Compile(
+    v8::String::NewFromUtf8(isolate, source.c_str()));
+  SamplerThread sampler(isolate);
+
+  sampler.Start();
+  script->Run();
+  sampler.Join();
+
+  int MAX_FRAMES_COUNT = v8::Sample::kMaxFramesCount;
+  CHECK_EQ(MAX_FRAMES_COUNT, sampler.sample.frames_count);
+}