AutoMemMap.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2; -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef loader_AutoMemMap_h
#define loader_AutoMemMap_h

#include "mozilla/FileUtils.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/RangedPtr.h"
#include "mozilla/Result.h"

#include <prio.h>

class nsIFile;

namespace mozilla {
namespace ipc {
class FileDescriptor;
}

namespace loader {

class AutoMemMap {
  typedef mozilla::ipc::FileDescriptor FileDescriptor;

 public:
  AutoMemMap() = default;

  ~AutoMemMap();

  Result<Ok, nsresult> init(nsIFile* file, int flags = PR_RDONLY, int mode = 0,
                            PRFileMapProtect prot = PR_PROT_READONLY);

  Result<Ok, nsresult> init(const FileDescriptor& file,
                            PRFileMapProtect prot = PR_PROT_READONLY,
                            size_t maybeSize = 0);

  void reset();

  bool initialized() const { return addr; }

  uint32_t size() const { return size_; }

  template <typename T = void>
  RangedPtr<T> get() {
    MOZ_ASSERT(addr);
    return {static_cast<T*>(addr), size_};
  }

  template <typename T = void>
  const RangedPtr<T> get() const {
    MOZ_ASSERT(addr);
    return {static_cast<T*>(addr), size_};
  }

  size_t nonHeapSizeOfExcludingThis() { return size_; }

  FileDescriptor cloneFileDescriptor() const;
  FileDescriptor cloneHandle() const;

  // Makes this mapping persistent. After calling this, the mapped memory
  // will remained mapped, even after this instance is destroyed.
  void setPersistent() { persistent_ = true; }

 private:
  Result<Ok, nsresult> initInternal(PRFileMapProtect prot,
                                    size_t maybeSize = 0);

  AutoFDClose fd;
  PRFileMap* fileMap = nullptr;

  uint32_t size_ = 0;
  void* addr = nullptr;

  bool persistent_ = 0;

  AutoMemMap(const AutoMemMap&) = delete;
  void operator=(const AutoMemMap&) = delete;
};

}  // namespace loader
}  // namespace mozilla

#endif  // loader_AutoMemMap_h