circular_buffer.h

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//
// To the LRM writer : this class is purely an artifact of the implementation.
//

#ifndef __CIRCULAR_BUFFER_H__
#define __CIRCULAR_BUFFER_H__

#include <iostream>

namespace tlm {

template < typename T >
class circular_buffer
{
public:

  explicit
  circular_buffer( int size = 0 );
  ~circular_buffer();

  void resize( int size );
  void clear();

  T read();
  void write( const T & );

  bool is_empty() const { return used() == 0; }
  bool is_full() const { return free() == 0; }

  int size() const { return m_size; }
  int used() const { return m_used; }
  int free() const { return m_free; }

  const T& read_data() const
    { return buf_read( m_buf, m_ri ); }

  const T& peek_data( int i ) const
    { return buf_read( m_buf, (m_ri + i) % size() ); }

  T & poke_data( int i )
    { return buf_read( m_buf , (m_wi + i) % size() ); }

  void debug() const;

private:
  void increment_write_pos( int i = 1 );
  void increment_read_pos( int i = 1 );

  void init();

  circular_buffer( const circular_buffer<T> &b );              // disabled
  circular_buffer<T> &operator=( const circular_buffer<T> & ); // disabled

  void* buf_alloc( int size );
  void  buf_free( void*& buf );
  void  buf_write( void* buf, int n, const T & t );
  T&    buf_read( void* buf, int n ) const;
  void  buf_clear( void* buf, int n );

private:
  int    m_size;                   // size of the buffer
  void*  m_buf;                    // the buffer
  int    m_free;                   // number of free spaces
  int    m_used;                   // number of used spaces
  int    m_ri;                     // index of next read
  int    m_wi;                     // index of next write

};

template< typename T >
void
circular_buffer<T>::debug() const
{

  std::cout << "Buffer debug" << std::endl;
  std::cout << "Size : " << size() << std::endl;
  std::cout << "Free/Used " << free() << "/" << used() << std::endl;
  std::cout << "Indices : r/w = " << m_ri << "/" << m_wi << std::endl;

  if( is_empty() ) {

    std::cout << "empty" << std::endl;

  }

  if( is_full() ) {

    std::cout << "full" << std::endl;

  }

  std::cout << "Data : " << std::endl;
  for( int i = 0; i < used(); i++ ) {

    std::cout << peek_data( i ) << std::endl;

  }


}

template < typename T >
circular_buffer<T>::circular_buffer( int size )
  : m_size(size)
  , m_buf(0)
{
  init();

}

template < typename T >
void
circular_buffer<T>::clear()
{
  for( int i=0; i < used(); i++ ) {
    buf_clear( m_buf, (m_ri + i) % m_size );
  }
  m_free = m_size;
  m_used = m_ri = m_wi = 0;
}

template < typename T >
circular_buffer<T>::~circular_buffer()
{
  clear();
  buf_free( m_buf );
}

template < typename T >
void
circular_buffer<T>::resize( int size )
{

  int i;
  void * new_buf = buf_alloc(size);

  for( i = 0; i < size && i < used(); i++ ) {

    buf_write( new_buf, i, peek_data( i ) );
    buf_clear( m_buf, (m_ri + i) % m_size );

  }

  buf_free( m_buf );

  m_size = size;
  m_ri   = 0;
  m_wi   = i % m_size;
  m_used = i;
  m_free = m_size - m_used;

  m_buf  = new_buf;
}


template < typename T >
void
circular_buffer<T>::init() {

  if( m_size > 0 ) {
    m_buf = buf_alloc( m_size );
  }

  m_free = m_size;
  m_used = 0;
  m_ri = 0;
  m_wi = 0;

}

template < typename T >
T
circular_buffer<T>::read()
{
  T t = read_data();

  buf_clear( m_buf, m_ri );
  increment_read_pos();

  return t;
}

template < typename T >
void
circular_buffer<T>::write( const T &t )
{
  buf_write( m_buf, m_wi, t );
  increment_write_pos();
}


template < typename T >
void
circular_buffer<T>::increment_write_pos( int i ) {

  m_wi = ( m_wi + i ) % m_size;
  m_used += i;
  m_free -= i;

}

template < typename T >
void
circular_buffer<T>::increment_read_pos( int i ) {

  m_ri = ( m_ri + i ) % m_size;
  m_used -= i;
  m_free += i;

}

template < typename T >
inline void*
circular_buffer<T>::buf_alloc( int size )
    { return new unsigned char[ size * sizeof(T) ]; }

template < typename T >
inline void
circular_buffer<T>::buf_free( void* & buf )
    { delete [] static_cast<unsigned char*>(buf); buf = 0; }

template < typename T >
inline void
circular_buffer<T>::buf_write( void* buf, int n, const T & t )
{
  T* p = static_cast<T*>(buf) + n;
  new (p) T(t);
}

template < typename T >
inline T&
circular_buffer<T>::buf_read( void* buf, int n ) const
{
  T* p = static_cast<T*>(buf) + n;
  return *p;
}

template < typename T >
inline void
circular_buffer<T>::buf_clear( void* buf, int n )
{
  T* p = static_cast<T*>(buf) + n;
  p->~T();
}

} // namespace tlm

#endif