v8-platform.h

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// Copyright 2013 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_V8_PLATFORM_H_
#define V8_V8_PLATFORM_H_
 
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>  // For abort.
#include <memory>
#include <string>
 
#include "v8config.h"  // NOLINT(build/include_directory)
 
namespace v8 {
 
class Isolate;
 
// Valid priorities supported by the task scheduling infrastructure.
enum class TaskPriority : uint8_t {
  kBestEffort,
  kUserVisible,
  kUserBlocking,
};
 
class Task {
 public:
  virtual ~Task() = default;
 
  virtual void Run() = 0;
};
 
class IdleTask {
 public:
  virtual ~IdleTask() = default;
  virtual void Run(double deadline_in_seconds) = 0;
};
 
class TaskRunner {
 public:
  virtual void PostTask(std::unique_ptr<Task> task) = 0;
 
  virtual void PostNonNestableTask(std::unique_ptr<Task> task) {}
 
  virtual void PostDelayedTask(std::unique_ptr<Task> task,
                               double delay_in_seconds) = 0;
 
  virtual void PostNonNestableDelayedTask(std::unique_ptr<Task> task,
                                          double delay_in_seconds) {}
 
  virtual void PostIdleTask(std::unique_ptr<IdleTask> task) = 0;
 
  virtual bool IdleTasksEnabled() = 0;
 
  virtual bool NonNestableTasksEnabled() const { return false; }
 
  virtual bool NonNestableDelayedTasksEnabled() const { return false; }
 
  TaskRunner() = default;
  virtual ~TaskRunner() = default;
 
  TaskRunner(const TaskRunner&) = delete;
  TaskRunner& operator=(const TaskRunner&) = delete;
};
 
class JobDelegate {
 public:
  virtual bool ShouldYield() = 0;
 
  virtual void NotifyConcurrencyIncrease() = 0;
};
 
class JobHandle {
 public:
  virtual ~JobHandle() = default;
 
  virtual void NotifyConcurrencyIncrease() = 0;
 
  virtual void Join() = 0;
 
  virtual void Cancel() = 0;
 
  virtual bool IsRunning() = 0;
};
 
class JobTask {
 public:
  virtual ~JobTask() = default;
 
  virtual void Run(JobDelegate* delegate) = 0;
 
  virtual size_t GetMaxConcurrency() const = 0;
};
 
class ConvertableToTraceFormat {
 public:
  virtual ~ConvertableToTraceFormat() = default;
 
  virtual void AppendAsTraceFormat(std::string* out) const = 0;
};
 
class TracingController {
 public:
  virtual ~TracingController() = default;
 
  // In Perfetto mode, trace events are written using Perfetto's Track Event
  // API directly without going through the embedder. However, it is still
  // possible to observe tracing being enabled and disabled.
#if !defined(V8_USE_PERFETTO)
 
  virtual const uint8_t* GetCategoryGroupEnabled(const char* name) {
    static uint8_t no = 0;
    return &no;
  }
 
  virtual uint64_t AddTraceEvent(
      char phase, const uint8_t* category_enabled_flag, const char* name,
      const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
      const char** arg_names, const uint8_t* arg_types,
      const uint64_t* arg_values,
      std::unique_ptr<ConvertableToTraceFormat>* arg_convertables,
      unsigned int flags) {
    return 0;
  }
  virtual uint64_t AddTraceEventWithTimestamp(
      char phase, const uint8_t* category_enabled_flag, const char* name,
      const char* scope, uint64_t id, uint64_t bind_id, int32_t num_args,
      const char** arg_names, const uint8_t* arg_types,
      const uint64_t* arg_values,
      std::unique_ptr<ConvertableToTraceFormat>* arg_convertables,
      unsigned int flags, int64_t timestamp) {
    return 0;
  }
 
  virtual void UpdateTraceEventDuration(const uint8_t* category_enabled_flag,
                                        const char* name, uint64_t handle) {}
#endif  // !defined(V8_USE_PERFETTO)
 
  class TraceStateObserver {
   public:
    virtual ~TraceStateObserver() = default;
    virtual void OnTraceEnabled() = 0;
    virtual void OnTraceDisabled() = 0;
  };
 
  virtual void AddTraceStateObserver(TraceStateObserver*) {}
 
  virtual void RemoveTraceStateObserver(TraceStateObserver*) {}
};
 
class PageAllocator {
 public:
  virtual ~PageAllocator() = default;
 
  virtual size_t AllocatePageSize() = 0;
 
  virtual size_t CommitPageSize() = 0;
 
  virtual void SetRandomMmapSeed(int64_t seed) = 0;
 
  virtual void* GetRandomMmapAddr() = 0;
 
  enum Permission {
    kNoAccess,
    kRead,
    kReadWrite,
    // TODO(hpayer): Remove this flag. Memory should never be rwx.
    kReadWriteExecute,
    kReadExecute
  };
 
  virtual void* AllocatePages(void* address, size_t length, size_t alignment,
                              Permission permissions) = 0;
 
  virtual bool FreePages(void* address, size_t length) = 0;
 
  virtual bool ReleasePages(void* address, size_t length,
                            size_t new_length) = 0;
 
  virtual bool SetPermissions(void* address, size_t length,
                              Permission permissions) = 0;
 
  virtual bool DiscardSystemPages(void* address, size_t size) { return true; }
};
 
class Platform {
 public:
  virtual ~Platform() = default;
 
  virtual PageAllocator* GetPageAllocator() {
    // TODO(bbudge) Make this abstract after all embedders implement this.
    return nullptr;
  }
 
  virtual void OnCriticalMemoryPressure() {
    // TODO(bbudge) Remove this when embedders override the following method.
    // See crbug.com/634547.
  }
 
  virtual bool OnCriticalMemoryPressure(size_t length) { return false; }
 
  virtual int NumberOfWorkerThreads() = 0;
 
  virtual std::shared_ptr<v8::TaskRunner> GetForegroundTaskRunner(
      Isolate* isolate) = 0;
 
  virtual void CallOnWorkerThread(std::unique_ptr<Task> task) = 0;
 
  virtual void CallBlockingTaskOnWorkerThread(std::unique_ptr<Task> task) {
    // Embedders may optionally override this to process these tasks in a high
    // priority pool.
    CallOnWorkerThread(std::move(task));
  }
 
  virtual void CallLowPriorityTaskOnWorkerThread(std::unique_ptr<Task> task) {
    // Embedders may optionally override this to process these tasks in a low
    // priority pool.
    CallOnWorkerThread(std::move(task));
  }
 
  virtual void CallDelayedOnWorkerThread(std::unique_ptr<Task> task,
                                         double delay_in_seconds) = 0;
 
  virtual bool IdleTasksEnabled(Isolate* isolate) { return false; }
 
  virtual std::unique_ptr<JobHandle> PostJob(
      TaskPriority priority, std::unique_ptr<JobTask> job_task) {
    return nullptr;
  }
 
  virtual double MonotonicallyIncreasingTime() = 0;
 
  virtual double CurrentClockTimeMillis() = 0;
 
  typedef void (*StackTracePrinter)();
 
  virtual StackTracePrinter GetStackTracePrinter() { return nullptr; }
 
  virtual TracingController* GetTracingController() = 0;
 
  virtual void DumpWithoutCrashing() {}
 
 protected:
  V8_EXPORT static double SystemClockTimeMillis();
};
 
}  // namespace v8
 
#endif  // V8_V8_PLATFORM_H_