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panda/src/putil/cycleDataReader.I

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// Filename: cycleDataReader.I
// Created by:  drose (21Feb02)
//
////////////////////////////////////////////////////////////////////
//
// PANDA 3D SOFTWARE
// Copyright (c) 2001, Disney Enterprises, Inc.  All rights reserved
//
// All use of this software is subject to the terms of the Panda 3d
// Software license.  You should have received a copy of this license
// along with this source code; you will also find a current copy of
// the license at http://www.panda3d.org/license.txt .
//
// To contact the maintainers of this program write to
// panda3d@yahoogroups.com .
//
////////////////////////////////////////////////////////////////////

#ifdef DO_PIPELINING
// This is the implementation for full support of pipelining (as well
// as the sanity-check only implementation).

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Constructor (full)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
CycleDataReader(const PipelineCycler<CycleDataType> &cycler) :
  _cycler(&cycler)
{
  _pointer = _cycler->read();
  _write_pointer = (CycleDataType *)NULL;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Copy Constructor (full)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
CycleDataReader(const CycleDataReader<CycleDataType> &copy) :
  _cycler(copy._cycler),
  _pointer(copy._pointer),
  _write_pointer(copy._write_pointer)
{
  nassertv(_pointer != (const CycleDataType *)NULL);
  // We cannot copy a CycleDataReader that has elevated itself to a
  // write pointer.
  nassertv(_write_pointer == (const CycleDataType *)NULL);
  _cycler->increment_read(_pointer);
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Copy Assignment (full)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE void CycleDataReader<CycleDataType>::
operator = (const CycleDataReader<CycleDataType> &copy) {
  _cycler = copy._cycler;
  _pointer = copy._pointer;
  _write_pointer = copy._write_pointer;

  nassertv(_pointer != (const CycleDataType *)NULL);
  // We cannot copy a CycleDataReader that has elevated itself to a
  // write pointer.
  nassertv(_write_pointer == (const CycleDataType *)NULL);
  _cycler->increment_read(_pointer);
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Destructor (full)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
~CycleDataReader() {
  if (_write_pointer != (CycleDataType *)NULL) {
    // If the _write_pointer is non-NULL, then someone called
    // elevate_to_write() at some point, and we now actually hold a
    // write pointer, not a read pointer.
    ((PipelineCycler<CycleDataType> *)_cycler)->release_write(_write_pointer);
  } else if (_pointer != (CycleDataType *)NULL) {
    _cycler->release_read(_pointer);
  }
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::operator -> (full)
//       Access: Public
//  Description: This provides an indirect member access to the actual
//               CycleData data.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE const CycleDataType *CycleDataReader<CycleDataType>::
operator -> () const {
  nassertr(_pointer != (const CycleDataType *)NULL, _cycler->cheat());
  return _pointer;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Typecast pointer (full)
//       Access: Public
//  Description: This allows the CycleDataReader to be passed to any
//               function that expects a const CycleDataType pointer.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
operator const CycleDataType * () const {
  nassertr(_pointer != (const CycleDataType *)NULL, _cycler->cheat());
  return _pointer;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::take_pointer (full)
//       Access: Public
//  Description: This is intended to be called only from
//               CycleDataWriter when it elevates the pointer from
//               read to write status.  This function returns the
//               reader's pointer and relinquishes ownership of the
//               pointer, rendering the reader invalid for future
//               reads.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE const CycleDataType *CycleDataReader<CycleDataType>::
take_pointer() {
  const CycleDataType *pointer = _pointer;
  _pointer = (CycleDataType *)NULL;
  _write_pointer = (CycleDataType *)NULL;
  nassertr(pointer != (const CycleDataType *)NULL, _cycler->cheat());
  return pointer;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::elevate_to_write (full)
//       Access: Public
//  Description: Call this to permanently elevate the readable pointer
//               to a writable pointer.  This returns a writable
//               pointer; subsequent calls to the same function will
//               trivially return the same writable pointer.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataType *CycleDataReader<CycleDataType>::
elevate_to_write(PipelineCycler<CycleDataType> &cycler) {
  nassertr(&cycler = &_cycler, cycler.cheat());
  if (_write_pointer == (CycleDataType *)NULL) {
    _write_pointer = cycler.elevate_read(_pointer);
    _pointer = _write_pointer;
  }
  return _write_pointer;
}

#else  // !DO_PIPELINING
// This is the trivial, do-nothing implementation.

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Constructor (trivial)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
CycleDataReader(const PipelineCycler<CycleDataType> &cycler) {
  _pointer = cycler.read();
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Copy Constructor (trivial)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
CycleDataReader(const CycleDataReader<CycleDataType> &copy) :
  _pointer(copy._pointer)
{
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Copy Assignment (trivial)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE void CycleDataReader<CycleDataType>::
operator = (const CycleDataReader<CycleDataType> &copy) {
  _pointer = copy._pointer;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Destructor (trivial)
//       Access: Public
//  Description:
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
~CycleDataReader() {
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::operator -> (trivial)
//       Access: Public
//  Description: This provides an indirect member access to the actual
//               CycleData data.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE const CycleDataType *CycleDataReader<CycleDataType>::
operator -> () const {
  return _pointer;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::Typecast pointer (trivial)
//       Access: Public
//  Description: This allows the CycleDataReader to be passed to any
//               function that expects a const CycleDataType pointer.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataReader<CycleDataType>::
operator const CycleDataType * () const {
  return _pointer;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::take_pointer (trivial)
//       Access: Public
//  Description: This is intended to be called only from
//               CycleDataWriter when it elevates the pointer from
//               read to write status.  This function returns the
//               reader's pointer and relinquishes ownership of the
//               pointer, rendering the reader invalid for future
//               reads.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE const CycleDataType *CycleDataReader<CycleDataType>::
take_pointer() {
  return _pointer;
}

////////////////////////////////////////////////////////////////////
//     Function: CycleDataReader::elevate_to_write (trivial)
//       Access: Public
//  Description: Call this to permanently elevate the readable pointer
//               to a writable pointer.  This returns a writable
//               pointer; subsequent calls to the same function will
//               trivially return the same writable pointer.
////////////////////////////////////////////////////////////////////
template<class CycleDataType>
INLINE CycleDataType *CycleDataReader<CycleDataType>::
elevate_to_write(PipelineCycler<CycleDataType> &cycler) {
  return (CycleDataType *)_pointer;
}

#endif  // DO_PIPELINING

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