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/*******************************************************************************
* fixedallocator.h
*
* Simple allocator using a fixed-size pool.
*
* Author: Christopher J. Cason.
*
* ---------------------------------------------------------------------------
* Persistence of Vision Ray Tracer ('POV-Ray') version 3.7.
* Copyright 1991-2013 Persistence of Vision Raytracer Pty. Ltd.
*
* POV-Ray is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* POV-Ray 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
* ---------------------------------------------------------------------------
* POV-Ray is based on the popular DKB raytracer version 2.12.
* DKBTrace was originally written by David K. Buck.
* DKBTrace Ver 2.0-2.12 were written by David K. Buck & Aaron A. Collins.
* ---------------------------------------------------------------------------
* $File: //depot/public/povray/3.x/source/backend/support/fixedallocator.h $
* $Revision: #1 $
* $Change: 6069 $
* $DateTime: 2013/11/06 11:59:40 $
* $Author: chrisc $
*******************************************************************************/
#if !defined __FIXED_ALLOCATOR_H__
#define __FIXED_ALLOCATOR_H__
#include <cassert>
namespace pov
{
template <typename T, int MaxElements>
class FixedAllocator
{
public:
typedef T value_type ;
typedef unsigned short size_type ;
typedef ptrdiff_t difference_type;
typedef T& reference ;
typedef const T& const_reference ;
typedef T *pointer ;
typedef const T *const_pointer ;
private:
size_type byteCount (unsigned char nItems) { return ((size_type) nItems * sizeof (T)) ; }
typedef struct
{
unsigned char nItems ;
unsigned char allocated ;
} BlockHeader ;
void defrag (void)
{
unsigned char current = m_FirstFreeBlock ;
while (current < MaxElements)
{
unsigned char next = current + m_Headers [current].nItems ;
if (next >= MaxElements)
break ;
if (m_Headers [current].allocated || m_Headers [next].allocated)
{
current = next ;
continue ;
}
m_Headers [current].nItems += m_Headers [next].nItems ;
m_Headers [next].nItems = 0 ;
}
}
unsigned char allocateBlocks (unsigned char nBlocks, unsigned char current)
{
assert (nBlocks > 0) ;
while (current < MaxElements)
{
unsigned char next = current + m_Headers [current].nItems ;
if (m_Headers [current].allocated == false && m_Headers [current].nItems >= nBlocks)
{
if (current + nBlocks < MaxElements && m_Headers [current].nItems > nBlocks)
{
m_Headers [current + nBlocks].nItems = m_Headers [current].nItems - nBlocks ;
m_Headers [current + nBlocks].allocated = false ;
}
m_Headers [current].nItems = nBlocks ;
m_Headers [current].allocated = true ;
if (m_FirstFreeBlock == current)
m_FirstFreeBlock = current + nBlocks ;
return (current) ;
}
current = next ;
}
return (0xff) ;
}
public:
// construct an allocator for the supplied new type.
template <typename N>
struct rebind { typedef FixedAllocator<N, MaxElements> other ; } ;
size_type max_size() const { return (MaxElements) ; }
pointer address (reference what) const { return (&what) ; }
const_pointer address (const_reference what) const { return (&what) ; }
FixedAllocator ()
{
if (MaxElements > 127)
throw POV_EXCEPTION_CODE(kInternalLimitErr, "Internal limit exceeded in fixedallocator.h") ;
m_FirstFreeBlock = 0 ;
m_Headers [0].allocated = false ;
m_Headers [0].nItems = MaxElements ;
}
~FixedAllocator () { }
void construct (pointer where, T const& what) { new (where) T (what) ; }
void destroy (pointer what) { what->~T() ; }
pointer allocate (size_type nItems, std::allocator<void>::const_pointer hint = 0)
{
if (((unsigned char *) hint >= m_Data) && ((unsigned char *) hint < m_Data + sizeof (T) * MaxElements))
{
unsigned char slot = ((unsigned char *) hint - m_Data) / sizeof (T) ;
if ((slot = allocateBlocks (nItems, slot)) != 0xff)
return ((pointer) (m_Data + byteCount (slot))) ;
}
unsigned char slot = allocateBlocks (nItems, m_FirstFreeBlock) ;
if (slot == 0xff)
{
defrag () ;
if ((slot = allocateBlocks (nItems, m_FirstFreeBlock)) == 0xff)
throw POV_EXCEPTION_CODE(kInternalLimitErr, "Internal limit exceeded in fixedallocator.h") ;
}
return ((pointer) (m_Data + byteCount (slot))) ;
}
void deallocate (pointer what, unsigned char nItems)
{
if (((unsigned char *) what >= m_Data) && ((unsigned char *) what < m_Data + sizeof (T) * MaxElements))
{
unsigned char slot = ((unsigned char *) what - m_Data) / sizeof (T) ;
if (m_Headers [slot].allocated && m_Headers [slot].nItems == nItems)
{
m_Headers [slot].allocated = false ;
if (m_FirstFreeBlock > slot)
{
m_FirstFreeBlock = slot ;
assert (m_Headers [slot].nItems > 0) ;
}
unsigned char next = slot + nItems ;
while (next < MaxElements && m_Headers [next].allocated == false)
{
m_Headers [slot].nItems += m_Headers [next].nItems ;
m_Headers [next].nItems = 0 ;
next = slot + m_Headers [slot].nItems ;
}
}
}
}
private:
unsigned char m_FirstFreeBlock ;
unsigned char m_Data [sizeof (T) * MaxElements] ;
BlockHeader m_Headers [MaxElements] ;
} ;
template <typename T>
class MallocAllocator
{
public:
typedef T value_type ;
typedef size_t size_type ;
typedef ptrdiff_t difference_type;
typedef T& reference ;
typedef const T& const_reference ;
typedef T *pointer ;
typedef const T *const_pointer ;
public:
// construct an allocator for the supplied new type.
template <typename N>
struct rebind { typedef MallocAllocator<N> other ; } ;
size_type max_size() const { return (0xffffffff) ; }
pointer address (reference what) const { return (&what) ; }
const_pointer address (const_reference what) const { return (&what) ; }
MallocAllocator () { }
~MallocAllocator () { }
void construct (pointer where, T const& what) { new (where) T (what) ; }
void destroy (pointer what) { what->~T() ; }
pointer allocate (size_type nItems, std::allocator<void>::const_pointer hint = 0)
{
return ((pointer) malloc (sizeof (T) * nItems)) ;
}
void deallocate (pointer what, size_type nItems)
{
free (what) ;
}
} ;
} // end namespace pov
#endif
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