1 // Copyright 2020 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include <include/cppgc/allocation.h>
6 #include <include/cppgc/default-platform.h>
7 #include <include/cppgc/garbage-collected.h>
8 #include <include/cppgc/heap.h>
9 #include <include/cppgc/member.h>
10 #include <include/cppgc/platform.h>
11 #include <include/cppgc/visitor.h>
12 #include <include/v8.h>
13
14 #include <iostream>
15 #include <memory>
16 #include <string>
17
18 /**
19 * This sample program shows how to set up a stand-alone cppgc heap as an
20 * embedder of V8. Most importantly, this example shows how to reuse V8's
21 * platform for cppgc.
22 */
23
24 /**
25 * Simple string rope to illustrate allocation and garbage collection below. The
26 * rope keeps the next parts alive via regular managed reference.
27 */
28 class Rope final : public cppgc::GarbageCollected<Rope> {
29 public:
Rope(std::string part,Rope * next=nullptr)30 explicit Rope(std::string part, Rope* next = nullptr)
31 : part_(part), next_(next) {}
32
Trace(cppgc::Visitor * visitor) const33 void Trace(cppgc::Visitor* visitor) const { visitor->Trace(next_); }
34
35 private:
36 std::string part_;
37 cppgc::Member<Rope> next_;
38
39 friend std::ostream& operator<<(std::ostream& os, const Rope& rope);
40 };
41
operator <<(std::ostream & os,const Rope & rope)42 std::ostream& operator<<(std::ostream& os, const Rope& rope) {
43 os << rope.part_;
44 if (rope.next_) {
45 os << *rope.next_;
46 }
47 return os;
48 }
49
main(int argc,char * argv[])50 int main(int argc, char* argv[]) {
51 // Create a platform that is used by cppgc::Heap for execution and backend
52 // allocation.
53 auto cppgc_platform = std::make_shared<cppgc::DefaultPlatform>();
54 // Initialize the process. This must happen before any cppgc::Heap::Create()
55 // calls.
56 cppgc::InitializeProcess(cppgc_platform->GetPageAllocator());
57 // Create a managed heap.
58 std::unique_ptr<cppgc::Heap> heap = cppgc::Heap::Create(cppgc_platform);
59 // Allocate a string rope on the managed heap.
60 auto* greeting = cppgc::MakeGarbageCollected<Rope>(
61 heap->GetAllocationHandle(), "Hello ",
62 cppgc::MakeGarbageCollected<Rope>(heap->GetAllocationHandle(), "World!"));
63 // Manually trigger garbage collection. The object greeting is held alive
64 // through conservative stack scanning.
65 heap->ForceGarbageCollectionSlow("V8 embedders example", "Testing");
66 std::cout << *greeting << std::endl;
67 // Gracefully shutdown the process.
68 cppgc::ShutdownProcess();
69 return 0;
70 }
71