geodesic_memory.h

//Copyright (C) 2008 Danil Kirsanov, MIT License
#ifndef _GEODESIC_MEMORY_20071231
#define _GEODESIC_MEMORY_20071231

//two fast and simple memory allocators

#include <vector>
#include <assert.h>
#include <math.h>
#include <memory>

namespace geodesic{

template<class T>			//quickly allocates multiple elements of a given type; no deallocation
class SimlpeMemoryAllocator
{
public:
	typedef T* pointer;

	SimlpeMemoryAllocator(unsigned block_size = 0, 
						  unsigned max_number_of_blocks = 0)
	{
		reset(block_size, 
			  max_number_of_blocks);
	};

	~SimlpeMemoryAllocator(){};

	void reset(unsigned block_size, 
			   unsigned max_number_of_blocks)
	{
		m_block_size = block_size;
		m_max_number_of_blocks = max_number_of_blocks;


		m_current_position = 0;

		m_storage.reserve(max_number_of_blocks);
		m_storage.resize(1);
		m_storage[0].resize(block_size);
	};

	pointer allocate(unsigned const n)		//allocate n units
	{
		assert(n < m_block_size);

		if(m_current_position + n >= m_block_size)
		{
			m_storage.push_back( std::vector<T>() );
			m_storage.back().resize(m_block_size);
			m_current_position = 0;
		}
		pointer result = & m_storage.back()[m_current_position];
		m_current_position += n;

		return result;
	};
private:
	std::vector<std::vector<T> > m_storage;	
	unsigned m_block_size;				//size of a single block
	unsigned m_max_number_of_blocks;		//maximum allowed number of blocks
	unsigned m_current_position;			//first unused element inside the current block
};


template<class T>		//quickly allocates and deallocates single elements of a given type
class MemoryAllocator
{
public:
	typedef T* pointer;

	MemoryAllocator(unsigned block_size = 1024, 
				    unsigned max_number_of_blocks = 1024)
	{
		reset(block_size, 
			  max_number_of_blocks);
	};

	~MemoryAllocator(){};

	void clear()
	{
		reset(m_block_size, 
			  m_max_number_of_blocks);
	}

	void reset(unsigned block_size, 
			   unsigned max_number_of_blocks)
	{
		m_block_size = block_size;
		m_max_number_of_blocks = max_number_of_blocks;

		assert(m_block_size > 0);
		assert(m_max_number_of_blocks > 0);

		m_current_position = 0;

		m_storage.reserve(max_number_of_blocks);
		m_storage.resize(1);
		m_storage[0].resize(block_size);

		m_deleted.clear();
		m_deleted.reserve(2*block_size);
	};

	pointer allocate()		//allocates single unit of memory
	{
		pointer result;
		if(m_deleted.empty())
		{
			if(m_current_position + 1 >= m_block_size)
			{
				m_storage.push_back( std::vector<T>() );
				m_storage.back().resize(m_block_size);
				m_current_position = 0;
			}
			result = & m_storage.back()[m_current_position];
			++m_current_position;
		}
		else
		{
			result = m_deleted.back();
			m_deleted.pop_back();
		}

		return result;
	};

	void deallocate(pointer p)		//allocate n units
	{
		if(m_deleted.size() < m_deleted.capacity())
		{
			m_deleted.push_back(p);
		}
	};

private:
	std::vector<std::vector<T> > m_storage;
	unsigned m_block_size;				//size of a single block
	unsigned m_max_number_of_blocks;		//maximum allowed number of blocks
	unsigned m_current_position;			//first unused element inside the current block

	std::vector<pointer> m_deleted;			//pointers to deleted elemets
};


class OutputBuffer
{
public:
	OutputBuffer():
		m_num_bytes(0)
	{}

	void clear()
	{
		m_num_bytes = 0;
		m_buffer = std::unique_ptr<double>();
	}

	template<class T>
	T* allocate(unsigned n)
	{
		double wanted = n*sizeof(T);
		if(wanted > m_num_bytes)
		{
			unsigned new_size = (unsigned) ceil(wanted / (double)sizeof(double));
			m_buffer = std::unique_ptr<double>(new double[new_size]);
			m_num_bytes = new_size*sizeof(double);
		}

		return (T*)m_buffer.get();
	}

	template <class T>
	T* get()
	{
		return (T*)m_buffer.get();
	}

	template<class T>
	unsigned capacity()
	{
		return (unsigned)floor((double)m_num_bytes/(double)sizeof(T));
	};

private:

	std::unique_ptr<double> m_buffer;
	unsigned m_num_bytes;
};


} //geodesic

#endif	//_GEODESIC_MEMORY_20071231