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// Copyright 2020 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.
#include <include/cppgc/allocation.h>
#include <include/cppgc/garbage-collected.h>
#include <include/cppgc/heap.h>
#include <include/cppgc/member.h>
#include <include/cppgc/platform.h>
#include <include/cppgc/visitor.h>
#include <include/libplatform/libplatform.h>
#include <include/v8.h>
#include <iostream>
#include <memory>
#include <string>
/**
* This sample program shows how to set up a stand-alone cppgc heap as an
* embedder of V8. Most importantly, this example shows how to reuse V8's
* platform for cppgc.
*/
/**
* Platform used by cppgc. Can just redirect to v8::Platform for most calls.
* Exception: GetForegroundTaskRunner(), see below.
*
* This example uses V8's default platform implementation to drive the cppgc
* platform.
*/
class Platform final : public cppgc::Platform {
public:
Platform() : v8_platform_(v8::platform::NewDefaultPlatform()) {}
cppgc::PageAllocator* GetPageAllocator() final {
return v8_platform_->GetPageAllocator();
}
double MonotonicallyIncreasingTime() final {
return v8_platform_->MonotonicallyIncreasingTime();
}
std::shared_ptr<cppgc::TaskRunner> GetForegroundTaskRunner() final {
// V8's default platform creates a new task runner when passed the
// v8::Isolate pointer the first time. For non-default platforms this will
// require getting the appropriate task runner.
return v8_platform_->GetForegroundTaskRunner(nullptr);
}
std::unique_ptr<cppgc::JobHandle> PostJob(
cppgc::TaskPriority priority,
std::unique_ptr<cppgc::JobTask> job_task) final {
return v8_platform_->PostJob(priority, std::move(job_task));
}
private:
std::unique_ptr<v8::Platform> v8_platform_;
};
/**
* Simple string rope to illustrate allocation and garbage collection below. The
* rope keeps the next parts alive via regular managed reference.
*/
class Rope final : public cppgc::GarbageCollected<Rope> {
public:
explicit Rope(std::string part, Rope* next = nullptr)
: part_(part), next_(next) {}
void Trace(cppgc::Visitor* visitor) const { visitor->Trace(next_); }
private:
std::string part_;
cppgc::Member<Rope> next_;
friend std::ostream& operator<<(std::ostream& os, const Rope& rope);
};
std::ostream& operator<<(std::ostream& os, const Rope& rope) {
os << rope.part_;
if (rope.next_) {
os << *rope.next_;
}
return os;
}
int main(int argc, char* argv[]) {
// Create a platform that is used by cppgc::Heap for execution and backend
// allocation.
auto cppgc_platform = std::make_shared<Platform>();
// Initialize the process. This must happen before any cppgc::Heap::Create()
// calls.
cppgc::InitializeProcess(cppgc_platform->GetPageAllocator());
// Create a managed heap.
std::unique_ptr<cppgc::Heap> heap = cppgc::Heap::Create(cppgc_platform);
// Allocate a string rope on the managed heap.
auto* greeting = cppgc::MakeGarbageCollected<Rope>(
heap->GetAllocationHandle(), "Hello ",
cppgc::MakeGarbageCollected<Rope>(heap->GetAllocationHandle(), "World!"));
// Manually trigger garbage collection. The object greeting is held alive
// through conservative stack scanning.
heap->ForceGarbageCollectionSlow("V8 embedders example", "Testing");
std::cout << *greeting << std::endl;
// Gracefully shutdown the process.
cppgc::ShutdownProcess();
return 0;
}
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