crown-engine/engine/core/containers/id_table.h

/*
Copyright (c) 2013 Daniele Bartolini, Michele Rossi
Copyright (c) 2012 Daniele Bartolini, Simone Boscaratto

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
*/

#pragma once

#include "assert.h"
#include "allocator.h"
#include "types.h"

namespace crown
{

/// Table of Ids.
///
/// @ingroup Containers
template <uint32_t MAX>
struct IdTable
{
	/// Creates the table for tracking exactly @a MAX - 1 unique Ids.
	IdTable();

	// The index of the first unused id.
	uint16_t m_freelist;

	// Next available unique id.
	uint16_t m_next_id;
	uint16_t m_size;

	// Table of ids.
	// The last valid id is reserved and cannot be used to
	// refer to Ids from the outside.
	Id m_ids[MAX];
};

/// Functions to manipulate IdTable.
///
/// @ingroup Containers
namespace id_table
{
	/// Creates a new Id in the table @a a and returns its value.
	template <uint32_t MAX> Id create(IdTable<MAX>& a);

	/// Destroys the @a id in the table @a a.
	template <uint32_t MAX> void destroy(IdTable<MAX>& a, Id id);

	/// Returns whether the table @a a has the given @a id.
	template <uint32_t MAX> bool has(const IdTable<MAX>& a, Id id);

	/// Returns the number of ids in the table @a a.
	template <uint32_t MAX> uint16_t size(const IdTable<MAX>& a);

	template <uint32_t MAX> const Id* begin(const IdTable<MAX>& a);
	template <uint32_t MAX> const Id* end(const IdTable<MAX>& a);
} // namespace id_table

namespace id_table
{
	//-----------------------------------------------------------------------------
	template <uint32_t MAX>
	inline Id create(IdTable<MAX>& a)
	{
		// Obtain a new id
		Id id;
		id.id = a.m_next_id++;

		// Recycle slot if there are any
		if (a.m_freelist != INVALID_ID)
		{
			id.index = a.m_freelist;
			a.m_freelist = a.m_ids[a.m_freelist].index;
		}
		else
		{
			id.index = a.m_size;
		}

		a.m_ids[id.index] = id;
		a.m_size++;

		return id;
	}

	//-----------------------------------------------------------------------------
	template <uint32_t MAX>
	inline void destroy(IdTable<MAX>& a, Id id)
	{
		CE_ASSERT(has(a, id), "IdTable does not have ID: %d,%d", id.id, id.index);

		a.m_ids[id.index].id = INVALID_ID;
		a.m_ids[id.index].index = a.m_freelist;
		a.m_freelist = id.index;
		a.m_size--;
	}

	//-----------------------------------------------------------------------------
	template <uint32_t MAX>
	inline bool has(const IdTable<MAX>& a, Id id)
	{
		return id.index < MAX && a.m_ids[id.index].id == id.id;
	}

	//-----------------------------------------------------------------------------
	template <uint32_t MAX>
	inline uint16_t size(const IdTable<MAX>& a)
	{
		return a.m_size;
	}

	//-----------------------------------------------------------------------------
	template <uint32_t MAX>
	inline const Id* begin(const IdTable<MAX>& a)
	{
		return a.m_ids;
	}

	//-----------------------------------------------------------------------------
	template <uint32_t MAX>
	inline const Id* end(const IdTable<MAX>& a)
	{
		return a.m_ids + MAX;
	}
} // namespace id_table

//-----------------------------------------------------------------------------
template <uint32_t MAX>
inline IdTable<MAX>::IdTable()
	: m_freelist(INVALID_ID)
	, m_next_id(0)
	, m_size(0)
{
	for (uint32_t i = 0; i < MAX; i++)
	{
		m_ids[i].id = INVALID_ID;
	}
}

} // namespace crown