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/* Copyright (C) 2003 MySQL AB
This program 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; version 2 of the License.
This program 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, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#ifndef CircularIndex_H
#define CircularIndex_H
//===========================================================================
//
// .DESCRIPTION
// Building block for circular buffers. It increment as a normal index.
// untill it it becomes the maximum size then it becomes zero.
//
// .TYPICAL USE:
// to implement a circular buffer.
//
// .EXAMPLE:
// See MemoryChannel.C
//===========================================================================
///////////////////////////////////////////////////////////////////////////////
// CircularIndex( int start= 0,int size=256 );
// Constuctor
// Parameters:
// start: where to start to index
// size : range of the index, will be from 0 to size-1
///////////////////////////////////////////////////////////////////////////////
// operator int ();
// returns the index
///////////////////////////////////////////////////////////////////////////////
// void operator ++ ();
// increments the index with one, of size is reached it is set to zero
///////////////////////////////////////////////////////////////////////////////
// friend int full( const CircularIndex& write, const CircularIndex& read );
// Taken the write index and the read index from a buffer it is calculated
// if the buffer is full
// Parameters:
// write: index used a write index for the buffer
// read : index used a read index for the buffer
// return
// 0 : not full
// 1 : full
///////////////////////////////////////////////////////////////////////////////
// friend int empty( const CircularIndex& write, const CircularIndex& read );
// Taken the write index and the read index from a buffer it is calculated
// if the buffer is empty
// Parameters:
// write: index used a write index for the buffer
// read : index used a read index for the buffer
// return
// 0 : not empty
// 1 : empty
///////////////////////////////////////////////////////////////////////////////
class CircularIndex
{
public:
inline CircularIndex( int start= 0,int size=256 );
operator int () const;
CircularIndex& operator ++ ();
friend int full( const CircularIndex& write, const CircularIndex& read );
friend int empty( const CircularIndex& write, const CircularIndex& read );
private:
int theSize;
int theIndex;
};
inline CircularIndex::operator int () const
{
return theIndex;
}
inline CircularIndex& CircularIndex::operator ++ ()
{
++theIndex;
if( theIndex >= theSize ){
theIndex= 0;
}
return *this;
}
inline int full( const CircularIndex& write, const CircularIndex& read )
{
int readTmp= read.theIndex;
if( read.theIndex < write.theIndex )
readTmp += read.theSize;
return ( readTmp - write.theIndex) == 1;
}
inline int empty( const CircularIndex& write, const CircularIndex& read )
{
return read.theIndex == write.theIndex;
}
inline CircularIndex::CircularIndex( int start,int size ):
theSize(size),
theIndex(start)
{
}
#endif
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