103 lines
3.6 KiB
C++
103 lines
3.6 KiB
C++
/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
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/*
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* Copyright (c) 2010 University of Washington
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation;
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef OUTPUT_STREAM_WRAPPER_H
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#define OUTPUT_STREAM_WRAPPER_H
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#include <fstream>
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#include "ns3/object.h"
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#include "ns3/ptr.h"
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#include "ns3/simple-ref-count.h"
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namespace ns3 {
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/**
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* @brief A class encapsulating an output stream.
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*
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* This class wraps a pointer to a C++ std::ostream and provides
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* reference counting of the object. This class is recommended for users
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* who want to pass output streams in the ns-3 APIs, such as in callbacks
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* or tracing.
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*
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* This class is motivated by the fact that in C++, copy and assignment of
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* iostreams is forbidden by std::basic_ios<>, because it is not possible
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* to predict the semantics of the stream desired by a user.
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*
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* When writing traced information to a file, the tempting ns-3 idiom is to
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* create a bound callback with an ofstream as the bound object. Unfortunately,
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* this implies a copy construction in order to get the ofstream object into the
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* callback. This operation, as mentioned above, is forbidden by the STL.
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* Using this class in ns-3 APIs is generally preferable to passing global
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* pointers to ostream objects, or passing a pointer to a stack allocated
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* ostream (which creates object lifetime issues).
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*
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* One could imagine having this object inherit from stream to get the various
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* overloaded operator<< defined, but we're going to be using a
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* Ptr<OutputStreamWrapper> when passing this object around. In this case, the
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* Ptr<> wouldn't understand the operators and we would have to dereference it
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* to access the underlying object methods. Since we would have to dereference
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* the Ptr<>, we don't bother and just expect the user to Get a saved pointer
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* to an ostream and dereference it him or herself. As in:
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*
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* \verbatim
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* void
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* TraceSink (Ptr<OutputStreamWrapper> streamWrapper, Ptr<const Packet> packet)
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* {
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* std::ostream *stream = streamWrapper->GetStream ();
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* *stream << "got packet" << std::endl;
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* }
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* \endverbatim
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*
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*
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* This class uses a basic ns-3 reference counting base class but is not
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* an ns3::Object with attributes, TypeId, or aggregation.
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*/
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class OutputStreamWrapper : public SimpleRefCount<OutputStreamWrapper>
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{
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public:
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/**
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* Constructor
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* \param filename file name
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* \param filemode std::ios::openmode flags
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*/
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OutputStreamWrapper (std::string filename, std::ios::openmode filemode);
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/**
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* Constructor
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* \param os output stream
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*/
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OutputStreamWrapper (std::ostream* os);
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~OutputStreamWrapper ();
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/**
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* Return a pointer to an ostream previously set in the wrapper.
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*
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* \see SetStream
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*
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* \returns a pointer to the encapsulated std::ostream
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*/
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std::ostream *GetStream (void);
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private:
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std::ostream *m_ostream; //!< The output stream
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bool m_destroyable; //!< Can be destroyed
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};
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} // namespace ns3
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#endif /* OUTPUT_STREAM_WRAPPER_H */
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