vmap/include/itextstream.h

/*
   Copyright (C) 2001-2006, William Joseph.
   All Rights Reserved.

   This file is part of GtkRadiant.

   GtkRadiant 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 2 of the License, or
   (at your option) any later version.

   GtkRadiant 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 GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#if !defined( INCLUDED_ITEXTSTREAM_H )
#define INCLUDED_ITEXTSTREAM_H

/// \file
/// \brief Text-stream interfaces.

#include <cstddef>
#include "generic/static.h"

/// \brief A read-only character-stream.
class TextInputStream
{
public:
/// \brief Attempts to read the next \p length characters from the stream to \p buffer.
/// Returns the number of characters actually stored in \p buffer.
virtual std::size_t read( char* buffer, std::size_t length ) = 0;
};

/// \brief A write-only character-stream.
class TextOutputStream
{
public:
/// \brief Attempts to write \p length characters to the stream from \p buffer.
/// Returns the number of characters actually read from \p buffer.
virtual std::size_t write( const char* buffer, std::size_t length ) = 0;
};

/// \brief Calls the overloaded function ostream_write() to perform text formatting specific to the type being written.
/*! Note that ostream_write() is not globally defined - it must be defined once for each type supported.\n
   To support writing a custom type MyClass to any kind of text-output-stream with operator<<:
   \code
   template<typename TextOutputStreamType>
   TextOutputStreamType& ostream_write(TextOutputStreamType& ostream, const MyClass& myClass)
   {
   return ostream << myClass.getName() << ' ' << myClass.getText();
   }
   \endcode
   Expressing this as a template allows it to be used directly with any concrete text-output-stream type, not just the abstract TextOutputStream\n
   \n
   This overload writes a single character to any text-output-stream - ostream_write(TextOutputStreamType& ostream, char c).
 */
template<typename T>
inline TextOutputStream& operator<<( TextOutputStream& ostream, const T& t ){
	return ostream_write( ostream, t );
}

class NullOutputStream : public TextOutputStream
{
public:
std::size_t write( const char*, std::size_t length ){
	return length;
}
};

class OutputStreamHolder
{
NullOutputStream m_nullOutputStream;
TextOutputStream* m_outputStream;
public:
OutputStreamHolder()
	: m_outputStream( &m_nullOutputStream ){
}
void setOutputStream( TextOutputStream& outputStream ){
	m_outputStream = &outputStream;
}
TextOutputStream& getOutputStream(){
	return *m_outputStream;
}
};

typedef Static<OutputStreamHolder> GlobalOutputStream;

/// \brief Returns the global output stream. Used to display messages to the user.
inline TextOutputStream& globalOutputStream(){
	return GlobalOutputStream::instance().getOutputStream();
}

class ErrorStreamHolder : public OutputStreamHolder {};
typedef Static<ErrorStreamHolder> GlobalErrorStream;

/// \brief Returns the global error stream. Used to display error messages to the user.
inline TextOutputStream& globalErrorStream(){
	return GlobalErrorStream::instance().getOutputStream();
}

#endif