isolate-allocator.h

// Copyright 2018 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_ISOLATE_ALLOCATOR_H_
#define V8_ISOLATE_ALLOCATOR_H_

#include "src/allocation.h"
#include "src/base/bounded-page-allocator.h"
#include "src/base/page-allocator.h"
#include "src/globals.h"

namespace v8 {

// Forward declarations.
namespace base {
class BoundedPageAllocator;
}

namespace internal {

// IsolateAllocator object is responsible for allocating memory for one (!)
// Isolate object. Depending on the allocation mode the memory can be allocated
// 1) in the C++ heap (when pointer compression is disabled)
// 2) in a proper part of a properly aligned region of a reserved address space
//   (when pointer compression is enabled).
//
// Isolate::New() first creates IsolateAllocator object which allocates the
// memory and then it constructs Isolate object in this memory. Once it's done
// the Isolate object takes ownership of the IsolateAllocator object to keep
// the memory alive.
// Isolate::Delete() takes care of the proper order of the objects destruction.
class V8_EXPORT_PRIVATE IsolateAllocator final {
 public:
  explicit IsolateAllocator(IsolateAllocationMode mode);
  ~IsolateAllocator();

  void* isolate_memory() const { return isolate_memory_; }

  v8::PageAllocator* page_allocator() const { return page_allocator_; }

  IsolateAllocationMode mode() {
    return reservation_.IsReserved() ? IsolateAllocationMode::kInV8Heap
                                     : IsolateAllocationMode::kInCppHeap;
  }

 private:
  Address InitReservation();
  void CommitPagesForIsolate(Address heap_base);

  // The allocated memory for Isolate instance.
  void* isolate_memory_ = nullptr;
  v8::PageAllocator* page_allocator_ = nullptr;
  std::unique_ptr<base::BoundedPageAllocator> page_allocator_instance_;
  VirtualMemory reservation_;

  DISALLOW_COPY_AND_ASSIGN(IsolateAllocator);
};

}  // namespace internal
}  // namespace v8

#endif  // V8_ISOLATE_ALLOCATOR_H_