povray/source/backend/support/simplevector.h

/*******************************************************************************
 * simplevector.h
 *
 * Very simple, basic vector-like classes containing just enough functionality
 * for their intended uses within POV. Flexibility is sacrificed for performance
 * as these classes will typically be used in places where they may constructed
 * and destroyed many millions of times per render. (For example, mediasky.pov
 * rendered at only 160x120 with no AA results in over 16 million instances of
 * construction of a FixedSimpleVector).
 *
 * These classes were added after extensive profiling pointed to a number of
 * instances of our use of std::vector causing slowdowns, particularly when
 * multiple threads were in use (due to locks in the RTL memory management used
 * to prevent heap corruption). Experiments with non-heap-based allocators (e.g.
 * refpools or thread-local storage) did improve the situation somewhat but weren't
 * enough, hence this file. At the time of writing we get about a 10% improvement
 * as compared to the old code.
 *
 * NOTE NOTE NOTE NOTE
 * -------------------
 * Be aware that these classes do NOT run destructors on contained objects.
 * This is intentional as we currently do not store any objects in them that
 * require this functionality.
 *
 * 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/simplevector.h $
 * $Revision: #1 $
 * $Change: 6069 $
 * $DateTime: 2013/11/06 11:59:40 $
 * $Author: chrisc $
 *******************************************************************************/

#ifndef __SIMPLEVECTOR__
#define __SIMPLEVECTOR__

#include <stdexcept>
#include "base/pov_err.h"

namespace pov
{

////////////////////////////////////////////////////////////////////////////
// Works like std::vector in some ways, but very limited and not at all as
// flexible. Does not implement all the methods of std::vector (just what
// is needed in POV). Has different allocation behaviour, which will probably
// need to be tweaked over time for best performance.
//
// Be aware that this class does NOT run destructors on contained objects.
// This is intentional as we currently do not store any objects in it that
// require this functionality. // TODO FIXME
////////////////////////////////////////////////////////////////////////////
template<class ContainerType, class Allocator = std::allocator<ContainerType> >
class SimpleVector
{
public:
	typedef SimpleVector<ContainerType> MyType;
	typedef size_t size_type;
	typedef size_t difference_type;
	typedef ContainerType *pointer;
	typedef ContainerType& reference;
	typedef ContainerType value_type;
	typedef const ContainerType *const_pointer;
	typedef const ContainerType& const_reference;
	typedef const ContainerType *const_iterator;
	typedef ContainerType *iterator;
	typedef Allocator allocator;
	typedef std::reverse_iterator<iterator> reverse_iterator;
	typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

	SimpleVector()
	{
		m_First = m_Last = m_End = NULL;
	}

	SimpleVector(size_type nItems, const ContainerType& InitialVal)
	{
		m_First = m_Last = m_End = NULL;
		if (nItems)
			allocate (nItems, InitialVal);
	}

	SimpleVector(const MyType& RHS)
	{
		if (RHS.m_First != RHS.m_Last)
		{
			allocate (RHS.capacity());
			for (pointer p = RHS.m_First ; p != RHS.m_Last ; )
				*m_Last++ = *p++;
		}
		else
			m_First = m_Last = m_End = NULL;
	}

	~SimpleVector()
	{
		// we don't call destructors, even if they exist
		if (m_First != NULL)
			deallocate ();
	}

	MyType& operator=(const MyType& RHS)
	{
		if (RHS.size() > capacity())
		{
			if (m_First != NULL)
				deallocate ();
			allocate (RHS.size());
		}
		m_Last = m_First;
		for (pointer p = RHS.m_First ; p != RHS.m_Last ; )
			*m_Last++ = *p++;
		return (*this);
	}

	size_type capacity() const
	{
		return (m_End - m_First);
	}

	iterator begin()
	{
		return (m_First);
	}

	const_iterator begin() const
	{
		return (m_First);
	}

	iterator end()
	{
		return (m_Last);
	}

	const_iterator end() const
	{
		return (m_Last);
	}

	reverse_iterator rbegin()
	{
		return (reverse_iterator (m_Last));
	}

	const_reverse_iterator rbegin() const
	{
		return (const_reverse_iterator (m_Last));
	}

	reverse_iterator rend()
	{
		return (reverse_iterator (m_First));
	}

	const_reverse_iterator rend() const
	{
		return (const_reverse_iterator (m_First));
	}

	size_type size() const
	{
		return (m_Last - m_First);
	}

	size_type max_size() const
	{
		return (alloc.max_size ());
	}

	bool empty() const
	{
		return (m_First == m_Last);
	}

	const_reference at(size_type Index) const
	{
		if (Index > size())
			throw std::out_of_range ("index out of range in SimpleVector::at");
		return (m_First [Index]);
	}

	reference at(size_type Index)
	{
		if (Index > size())
			throw std::out_of_range ("index out of range in SimpleVector::at");
		return (m_First [Index]);
	}

	const_reference operator[](size_type Index) const
	{
		return (m_First [Index]);
	}

	reference operator[](size_type Index)
	{
		return (m_First [Index]);
	}

	reference front()
	{
		return (*m_First);
	}

	const_reference front() const
	{
		return (*m_First);
	}

	reference back()
	{
		return (*(m_Last - 1));
	}

	const_reference back() const
	{
		return (*(m_Last - 1));
	}

	void push_back(const ContainerType& NewVal)
	{
		if (m_Last < m_End)
		{
			*m_Last++ = NewVal;
			return;
		}
		insert(m_Last, NewVal);
	}

	void pop_back()
	{
		if (m_Last > m_First)
			--m_Last;
	}

	iterator insert(iterator Where, const ContainerType& NewVal)
	{
		size_type Index = 0;

		if (m_Last > m_First)
			Index = Where - m_First;

		if (m_Last == m_End)
		{
			size_type c = size() + 1;
			size_type n = capacity();
			size_type nc = n * 2;
			if (nc < 8)
				nc = 8;
			pointer p = alloc.allocate (nc);
			p [Index] = NewVal;
			for (size_type i = 0 ; i < Index ; i++)
				p [i] = m_First [i];
			for (size_type i = Index + 1 ; i < c ; i++)
				p [i] = m_First [i];
			if (m_First != NULL)
				alloc.deallocate (m_First, n);
			m_First = p;
			m_End = m_First + nc;
			m_Last = m_First + c;
			return (m_First + Index);
		}

		if (Index == size())
		{
			*m_Last = NewVal;
			return (m_Last++);
		}

		for (size_type i = size() ; i > Index ; i--)
			m_First [i] = m_First [i - 1];
		m_Last++;
		m_First [Index] = NewVal;
		return (m_First + Index);
	}

	iterator erase(iterator What)
	{
		size_type Index = What - begin();

		if (What == m_Last - 1)
			return (m_Last--);

		for (pointer p1 = What, p2 = What + 1 ; p2 < m_Last ; )
			*p1++ = *p2++;
		m_Last--;
		return (++What);
	}

	void clear()
	{
		m_Last = m_First;
	}

private:
	void allocate (size_type nItems)
	{
		m_Last = m_First = alloc.allocate (nItems);
		m_End = m_First + nItems;
	}

	void allocate (size_type nItems, const ContainerType& InitialVal)
	{
		m_Last = m_First = alloc.allocate (nItems);
		m_End = m_First + nItems;
		while (nItems--)
			*m_Last++ = InitialVal;
	}

	void deallocate ()
	{
		alloc.deallocate (m_First, m_End - m_First);
	}

	allocator alloc;
	pointer m_First;
	pointer m_End;
	pointer m_Last;
};

////////////////////////////////////////////////////////////////////////////
// This template class requires a maximum size (ElementCount) and maintains
// its storage internally (typically therefore this will end up on the stack
// rather than being allocated upon request). The up side to this behaviour
// is that no time is spent obtaining memory from a pool, or for that matter
// copying data if a reallocation is needed. The down side is that firstly
// it cannot expand beyond the maximum size specified, and secondly that
// binary copies of the object take longer because they contain the entire
// storage (even if no entries are allocated).
//
// Be aware that this class does NOT run destructors on contained objects.
// This is intentional as we currently do not store any objects in it that
// require this functionality.
////////////////////////////////////////////////////////////////////////////
template<class ContainerType, int ElementCount>
class FixedSimpleVector
{
public:
	typedef FixedSimpleVector<ContainerType, ElementCount> MyType;
	typedef size_t size_type;
	typedef size_t difference_type;
	typedef ContainerType *pointer;
	typedef ContainerType& reference;
	typedef ContainerType value_type;
	typedef const ContainerType *const_pointer;
	typedef const ContainerType& const_reference;
	typedef const ContainerType *const_iterator;
	typedef ContainerType *iterator;
	typedef std::reverse_iterator<iterator> reverse_iterator;
	typedef std::reverse_iterator<const_iterator> const_reverse_iterator;

	FixedSimpleVector() :
		m_Last ((pointer) m_Data),
		m_End (pointer (m_Data) + ElementCount)
	{
	}

	FixedSimpleVector(size_type nItems, const ContainerType& InitialVal) :
		m_Last ((pointer) m_Data),
		m_End (pointer (m_Data) + ElementCount)
	{
		if (nItems > ElementCount)
			throw POV_EXCEPTION(pov_base::kInternalLimitErr, "Internal limit exceeded in FixedSimpleVector");
		while (nItems--)
			*m_Last++ = InitialVal;
	}

	FixedSimpleVector(const MyType& RHS) :
		m_Last ((pointer) m_Data),
		m_End (pointer (m_Data) + ElementCount)
	{
		for (pointer p = pointer (RHS.m_Data) ; p != RHS.m_Last ; )
			*m_Last++ = *p++;
	}

	~FixedSimpleVector()
	{
		// we don't call destructors, even if they exist
	}

	MyType& operator=(const MyType& RHS)
	{
		if (RHS.size() > ElementCount)
			throw POV_EXCEPTION(pov_base::kInternalLimitErr, "Internal limit exceeded in FixedSimpleVector");
		m_Last = pointer (m_Data);
		for (pointer p = pointer (RHS.m_Data) ; p != RHS.m_Last ; )
			*m_Last++ = *p++;
		return (*this);
	}

	size_type capacity() const
	{
		return (ElementCount);
	}

	iterator begin()
	{
		return (reinterpret_cast<pointer>(&(m_Data[0])));
	}

	const_iterator begin() const
	{
		return (reinterpret_cast<const_pointer>(&(m_Data[0])));
	}

	iterator end()
	{
		return (m_Last);
	}

	const_iterator end() const
	{
		return (m_Last);
	}

	reverse_iterator rbegin()
	{
		return (reverse_iterator (m_Last));
	}

	const_reverse_iterator rbegin() const
	{
		return (const_reverse_iterator (m_Last));
	}

	reverse_iterator rend()
	{
		return (reverse_iterator (pointer (m_Data)));
	}

	const_reverse_iterator rend() const
	{
		return (const_reverse_iterator (pointer (m_Data)));
	}

	size_type size() const
	{
		return (m_Last - const_pointer (m_Data));
	}

	size_type max_size() const
	{
		return (ElementCount);
	}

	bool empty() const
	{
		return (const_pointer (m_Data) == m_Last);
	}

	const_reference at(size_type Index) const
	{
		if (Index > size())
			throw std::out_of_range ("index out of range in FixedSimpleVector::at");
		return (pointer (m_Data) [Index]);
	}

	reference at(size_type Index)
	{
		if (Index > size())
			throw std::out_of_range ("index out of range in FixedSimpleVector::at");
		return (pointer (m_Data) [Index]);
	}

	const_reference operator[](size_type Index) const
	{
		return (pointer (m_Data) [Index]);
	}

	reference operator[](size_type Index)
	{
		return (pointer (m_Data) [Index]);
	}

	reference front()
	{
		return (*pointer (m_Data));
	}

	const_reference front() const
	{
		return (*pointer (m_Data));
	}

	reference back()
	{
		return (*(m_Last - 1));
	}

	const_reference back() const
	{
		return (*(m_Last - 1));
	}

	void push_back(const ContainerType& NewVal)
	{
		if (m_Last == m_End)
			throw POV_EXCEPTION(pov_base::kInternalLimitErr, "Internal limit exceeded in FixedSimpleVector");
		*m_Last++ = NewVal;
	}

	void pop_back()
	{
		if (m_Last > pointer (m_Data))
			--m_Last;
	}

	iterator insert(iterator Where, const ContainerType& NewVal)
	{
		if (m_Last == m_End)
			throw POV_EXCEPTION(pov_base::kInternalLimitErr, "Internal limit exceeded in FixedSimpleVector");
		for (pointer p1 = Where, p2 = Where + 1 ; p1 < m_Last ; )
			*p2++ = *p1++;
		m_Last++;
		*Where = NewVal;
		return (Where);
	}

	iterator erase(iterator Where)
	{
		if (Where == m_End)
			throw POV_EXCEPTION(pov_base::kInternalLimitErr, "Attempt to erase past end of vector");
		if (Where == m_Last - 1)
			return (m_Last--);
		for (pointer p1 = Where, p2 = Where + 1 ; p2 < m_Last ; )
			*p1++ = *p2++;
		m_Last--;
		return (++Where);
	}

	void clear()
	{
		m_Last = pointer (m_Data);
	}

private:
	unsigned char m_Data [sizeof (value_type) * ElementCount];
	const pointer m_End;
	pointer m_Last;
};

}

#endif