gecko/xpcom/glue/FileUtils.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
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 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla code.
 *
 * The Initial Developer of the Original Code is
 * Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2010
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Benjamin Smedberg <benjamin@smedbergs.us>
 *   Taras Glek <tglek@mozilla.com>
 *
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 * either the GNU General Public License Version 2 or later (the "GPL"), or
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#ifndef mozilla_FileUtils_h
#define mozilla_FileUtils_h

#if defined(XP_UNIX)
# include <unistd.h>
#elif defined(XP_WIN)
# include <io.h>
#endif
#include "prio.h"

namespace mozilla {

/**
 * AutoFDClose is a RAII wrapper for PRFileDesc.
 **/
class AutoFDClose
{
public:
  AutoFDClose(PRFileDesc* fd = nsnull) : mFD(fd) { }
  ~AutoFDClose() { if (mFD) PR_Close(mFD); }

  PRFileDesc* operator= (PRFileDesc *fd) {
    if (mFD) PR_Close(mFD);
    mFD = fd;
    return fd;
  }

  operator PRFileDesc* () { return mFD; }
  PRFileDesc** operator &() { *this = nsnull; return &mFD; }

private:
  PRFileDesc *mFD;
};

/**
 * Instances close() their fds when they go out of scope.
 */
struct ScopedClose
{
  ScopedClose(int aFd=-1) : mFd(aFd) {}
  ~ScopedClose() {
    if (0 <= mFd) {
      close(mFd);
    }
  }
  int mFd;
};

/**
 * Fallocate efficiently and continuously allocates files via fallocate-type APIs.
 * This is useful for avoiding fragmentation.
 * On sucess the file be padded with zeros to grow to aLength.
 *
 * @param aFD file descriptor.
 * @param aLength length of file to grow to.
 * @return true on success.
 */
NS_COM_GLUE bool fallocate(PRFileDesc *aFD, PRInt64 aLength);

} // namespace mozilla
#endif