AutoObjectMapper.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* 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 AutoObjectMapper_h

#define AutoObjectMapper_h

#include <string>

#include "mozilla/Attributes.h"

#include "PlatformMacros.h"

// A (nearly-) RAII class that maps an object in and then unmaps it on

// destruction.  This base class version uses the "normal" POSIX

// functions: open, fstat, close, mmap, munmap.

class MOZ_STACK_CLASS AutoObjectMapperPOSIX {

 public:

  // The constructor does not attempt to map the file, because that

  // might fail.  Instead, once the object has been constructed,

  // call Map() to attempt the mapping.  There is no corresponding

  // Unmap() since the unmapping is done in the destructor.  Failure

  // messages are sent to |aLog|.

  explicit AutoObjectMapperPOSIX(void (*aLog)(const char*));

  // Unmap the file on destruction of this object.

  ~AutoObjectMapperPOSIX();

  // Map |fileName| into the address space and return the mapping

  // extents.  If the file is zero sized this will fail.  The file is

  // mapped read-only and private.  Returns true iff the mapping

  // succeeded, in which case *start and *length hold its extent.

  // Once a call to Map succeeds, all subsequent calls to it will

  // fail.

  bool Map(/*OUT*/ void** start, /*OUT*/ size_t* length, std::string fileName);

 protected:

  // If we are currently holding a mapped object, these record the

  // mapped address range.

  void* mImage;

  size_t mSize;

  // A logging sink, for complaining about mapping failures.

  void (*mLog)(const char*);

 private:

  // Are we currently holding a mapped object?  This is private to

  // the base class.  Derived classes need to have their own way to

  // track whether they are holding a mapped object.

  bool mIsMapped;

  // Disable copying and assignment.

  AutoObjectMapperPOSIX(const AutoObjectMapperPOSIX&);

  AutoObjectMapperPOSIX& operator=(const AutoObjectMapperPOSIX&);

  // Disable heap allocation of this class.

  void* operator new(size_t);

  void* operator new[](size_t);

  void operator delete(void*);

  void operator delete[](void*);

};

#endif  // AutoObjectMapper_h