databuffer.h

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/*
 * This file is part of Ambulant Player, www.ambulantplayer.org.
 *
 * Copyright (C) 2003-2007 Stichting CWI, 
 * Kruislaan 413, 1098 SJ Amsterdam, The Netherlands.
 *
 * Ambulant Player is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * Ambulant Player 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Ambulant Player; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

 
 
#ifndef AMBULANT_NET_DATABUFFER_H
#define AMBULANT_NET_DATABUFFER_H
#include "ambulant/config/config.h"

#include "ambulant/lib/mtsync.h"

//////////////////////////////////////
#ifndef AMBULANT_NO_IOSTREAMS_HEADERS

#include <iostream>
#ifndef AMBULANT_NO_OSTREAM
#include <ostream>
#else /*AMBULANT_NO_OSTREAM*/
#include <ostream.h>
#endif/*AMBULANT_NO_OSTREAM*/

#endif // AMBULANT_NO_IOSTREAMS_HEADERS
//////////////////////////////////////

namespace ambulant {

namespace net {

typedef char bytes; 

/// Class to hold data bytes.
/// Data can be pushed in (at the back) and pulled out (at the
/// front), and it is possible to set the maximum size of the
/// buffer. In addition you can control when to free the unused space
/// in the buffer.
class AMBULANTAPI databuffer  
{							
  public:
	// constructors
	databuffer(int max_size=0);	
	// destructor
	~databuffer();

	
#ifndef AMBULANT_NO_IOSTREAMS_HEADERS
	// show information about the buffer, if verbose is true the buffer contents are dumped to cout.
	void dump(std::ostream& os, bool verbose) const;		
#endif // AMBULANT_NO_IOSTREAMS_HEADERS
	

	/// Returns the number of bytes in the buffer.
	/// Cannot be called between get_read_ptr/readdone.
	int  size() const;
	
	/// Return true if the buffer is full.
 	bool buffer_full();
	/// Return true if the buffer is non-empty.
    bool buffer_not_empty();
	
	/// Prepare to write size bytes of data.
	/// Returns a pointer at which the bytes can be written.
	char* get_write_ptr(int size);
	
	/// Finish writing data.
	/// Size must be less or equal to the size passed to the get_write_ptr call.
	void  pushdata(int size);

	/// Prepare to read data.
	/// Returns a pointer from which at most size() bytes can be read.
    char* get_read_ptr();
	
	
	/// Finish reading data.
	void readdone(int size);
	
	/// Set the maximum size for the buffer.
	/// When the buffer becomes this full buffer_full() will start returning true.
	/// Pass zero to set the size to unlimited.
	void set_max_size(int max_size);
	
	/// Set the maximum unused size of the buffer.
	/// As soon as this many unused bytes are occupied by the buffer
	/// we reallocate and copy the data to free the unused space.
	void set_max_unused_size(int max_unused_size);

	/// Class method to set default value for max_size.
	static void default_max_size(int max_size);
	
	/// Class method to set default for max_unused_size.
	static void default_max_unused_size(int max_unused_size);
  private:
	// Add space to the end of the buffer
	void _grow(int sz);
	
    char* m_buffer;			// Our databuffer
    bool m_reading;			// True between get_read_ptr/readdone
	bool m_writing;			// True between get_write_ptr/pushdata
  	char* m_old_buffer;		// An old buffer, to be removed in readdone
	unsigned long int m_rear;
	unsigned long int m_size;
 	unsigned long int m_max_size;
	unsigned long int m_max_unused_size;
	unsigned long int m_used;
	bool m_buffer_full;
	lib::critical_section m_lock;
	
	static long int s_default_max_size;
	static long int s_default_max_unused_size;
};

#ifndef AMBULANT_NO_IOSTREAMS_HEADERS
inline std::ostream& operator<<(std::ostream& os, const databuffer& n) {
		os << "databuffer(" << (void *)&n << ", used=" << n.size() << ")";
		return os;
	}
#endif // AMBULANT_NO_IOSTREAMS_HEADERS
	
} // end namespace net

} //end namespace ambulant
	
#endif