File: sbuild-mntstream.h

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/* Copyright © 2003,2006-2008  Roger Leigh <rleigh@debian.org>
 *
 * schroot is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * schroot is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 *********************************************************************/

#ifndef SBUILD_MNTSTREAM_H
#define SBUILD_MNTSTREAM_H

#include <sbuild/sbuild-custom-error.h>

#include <iostream>
#include <deque>
#include <string>

#include <stdio.h>
#include <sys/types.h>
#include <mntent.h>

namespace sbuild
{

  /**
   * Access mounts.  This is a wrapper around the setmntent(3),
   * getmntent(3) and endmntent(3) functions, which are used to read a
   * stream of "mntents" through multiple getmntent() calls.
   *
   * mntstream calls setmntent() and endmntent() automatically, and
   * represents each mntent as a mntstream::mntentry.  Like reading
   * from and istream by pulling data out with the >> "extraction
   * operator", mntentries are also extracted from the mntstream with
   * the >> operator.
   */
  class mntstream
    {
    public:
      /// Error codes.
      enum error_code
	{
	  MNT_OPEN, ///< Failed to open mount file.
	  MNT_READ  ///< Failed to read mount file.
	};

      /// Exception type.
      typedef sbuild::custom_error<error_code> error;

      /**
       * An entry in a mntstream.  It is a wrapper around the mntent
       * structure declared in mntent.h.  Unlike a mntent pointer returned
       * by getmntent(3), a mntentry does not become invalid when the
       * mntstream it was extracted from is destroyed.
       */
      struct mntentry
      {
	/// The constructor.
	mntentry ()
	{};

	/**
	 * The contructor.
	 *
	 * @param entry the mntent structure to wrap.
	 */
	mntentry (struct mntent const&  entry);

	/// Name of mounted filesystem.
	std::string  filesystem_name;
	/// File system path prefix.
	std::string  directory;
	/// Mount type.
	std::string  type;
	/// Mount options.
	std::string  options;
	/// Dump frequency (days).
	int          dump_frequency;
	/// Parallel fsck pass number.
	int          fsck_pass;
      };

      /**
       * The constructor.
       *
       * @param file the file to read.
       */
      mntstream(std::string const& file);

      /// The destructor.
      virtual ~mntstream();

      /**
       * Open a mount file for reading.  This uses the openmnt(3) call
       * to open the underlying FILE stream.  Any previously open
       * mount file is closed before opening the new one.  The
       * mntstream error state is set if the open fails, and an
       * exception will be thrown.
       *
       * @param file the file to read.
       * @see close()
       */
      void open(std::string const& file);

      /**
       * Close the mount file.  This uses the closemnt(3) call to
       * close the underlying FILE stream.  All cached data is deleted
       * and the error state set until open() is called.
       *
       * @see open()
       */
      void close();

      /**
       * Check for End Of File.  Note that the end of file status is
       * only set adter a read fails, so this should be checked after
       * each read.
       *
       * @returns true if the mntstream is empty, otherwise false.
       */
      bool eof() const;

      /**
       * Check for errors.  If there is an error, the mntstream is
       * unusable until the next open() call.
       *
       * @returns true if the mntstream is in an error state, otherwise
       * false.
       */
      bool bad() const;

      /**
       * Check if the mntstream status is good.
       *
       * @returns true if the status is good (eof() and bad() both
       * return false).
       */
      operator bool ();

      /**
       * Check if the mntstream status is bad.
       *
       * @returns true if the status is bad (eof() or bad() return
       * true).
       */
      bool
      operator ! ();

      friend mntstream&
      operator >> (mntstream& stream,
		   mntentry&  entry);

    private:
      /**
       * Read mntents from the underlying FILE stream into the data
       * deque.  If the read fails, the error state will be set, and
       * an exception will be thrown.
       *
       * @param quantity the number of mntents to read.
       *
       * @todo Add mntentry constructor to do automatic struct mntent
       * to mntentry conversion.
       */
      void read (int quantity=1);

      /// The file name.
      std::string file;

      /// The underlying FILE stream.
      FILE *mntfile;

      /**
       * A list of mntentries represents the mount file stream as a
       * LIFO stack.
       */
      std::deque<mntentry> data;

      /// Error status.
      bool error_status;

      /// End of File status.
      bool eof_status;
  };

  /**
   * The overloaded extraction operator.  This is used to pull
   * mntentries from a mntstream.
   *
   * @param stream the mntstream to get input from.
   * @param entry the mntentry to set.
   * @returns the mntstream.
   */
  mntstream&
  operator >> (mntstream&            stream,
	       mntstream::mntentry&  entry);

}

#endif /* SBUILD_MNTSTREAM_H */

/*
 * Local Variables:
 * mode:C++
 * End:
 */