DoorKeeper/include/doorkeeper/implem/saltedid.hpp

/* Copyright 2015, Michele Santullo
 * This file is part of DoorKeeper.
 *
 * DoorKeeper is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * DoorKeeper 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with DoorKeeper.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef id440C878EF94C4468948A57610C7C9B5A
#define id440C878EF94C4468948A57610C7C9B5A

#include "doorkeeper/primitivetypes.hpp"
#include "doorkeeper/implem/dktypes.hpp"
#include <ciso646>

namespace dk {
	namespace implem {
		template <unsigned int S>
		struct uint_t {
			typedef typename int_t<S / CHAR_BIT, false>::type type;
		};

		template <unsigned int N, unsigned int M=8*CHAR_BIT, bool=(N>=M) or (N%CHAR_BIT==0)>
		struct RoundToInt {
		private:
			enum {
				v = (N < M ? (N < CHAR_BIT ? CHAR_BIT : N) : M)
			};
			static_assert(v > 0, "v must be greater than 0");

		public:
			enum {
				value = ((((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) | ((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) >> 4)) | (((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) | ((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) >> 4)) >> 8)) | ((((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) | ((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) >> 4)) | (((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) | ((((v - 1) | ((v - 1) >> 1)) | (((v - 1) | ((v - 1) >> 1)) >> 2)) >> 4)) >> 8)) >> 16)) + 1
			};
			static_assert(value <= M, "value must be smaller than M");
			static_assert(value and not (value bitand (value - 1)), "value must be a power of two");
		};

		template <unsigned int B>
		struct FillBits;
		template <unsigned int B>
		struct FillBits {
			enum { value = 1 bitor (FillBits<B - 1>::value << 1) };
		};
		template <>
		struct FillBits<0> {
			enum { value = 0 };
		};

	} //namespace implem

	template <unsigned int Salt, unsigned int Indx>
	class SaltedID {
		static_assert(Salt + Indx <= 64, "Only indices up to 64 bits are currently supported");
	public:
		enum {
			bit_size = implem::RoundToInt<Salt + Indx>::value,
			max_index = implem::FillBits<Indx>::value,
			max_salt = implem::FillBits<Salt>::value
		};
	private:

		typedef typename implem::uint_t<bit_size>::type compound_type;
	public:
		typedef typename implem::uint_t<implem::RoundToInt<Salt>::value>::type salt_type;
		typedef typename implem::uint_t<implem::RoundToInt<Indx>::value>::type index_type;

		SaltedID ( void ) { }
		SaltedID ( index_type parIndex, salt_type parSalt ) :
			m_data(pack_index_salt(parIndex, parSalt))
		{
			DK_ASSERT(index() == parIndex);
			DK_ASSERT(salt() == parSalt);
		}

		salt_type salt ( void ) const;
		index_type index ( void ) const;

		SaltedID& operator+= ( index_type parOther ) { m_data = pack_index_salt(index() + parOther, salt()); return *this; }
		SaltedID& operator-= ( index_type parOther ) { m_data = pack_index_salt(index() - parOther, salt()); return *this; }

	private:
		static compound_type pack_index_salt ( index_type parIndex, salt_type parSalt );

		compound_type m_data;
	};

	template <unsigned int Salt, unsigned int Indx>
	auto SaltedID<Salt, Indx>::salt() const -> salt_type {
		return static_cast<salt_type>(m_data bitand implem::FillBits<Salt>::value);
	}

	template <unsigned int Salt, unsigned int Indx>
	auto SaltedID<Salt, Indx>::index() const -> index_type {
		return static_cast<index_type>(m_data >> Salt);
	}

	template <unsigned int Salt, unsigned int Indx>
	auto SaltedID<Salt, Indx>::pack_index_salt (index_type parIndex, salt_type parSalt) -> compound_type {
		DK_ASSERT(parIndex <= max_index);
		DK_ASSERT(parSalt <= max_salt);
		return (static_cast<compound_type>(parIndex) << Salt) bitor parSalt;
	}

	template <unsigned int Salt, unsigned int Indx>
	inline bool operator< (const SaltedID<Salt, Indx>& parLeft, const SaltedID<Salt, Indx>& parRight) {
		return parLeft.index() < parRight.index();
	}

	template <unsigned int Salt, unsigned int Indx>
	inline SaltedID<Salt, Indx> operator+ (SaltedID<Salt, Indx> parLeft, typename SaltedID<Salt, Indx>::index_type parRight) {
		return (parLeft += parRight);
	}

	template <unsigned int Salt, unsigned int Indx>
	inline SaltedID<Salt, Indx> operator+ (typename SaltedID<Salt, Indx>::index_type parLeft, SaltedID<Salt, Indx> parRight) {
		return (parRight += parLeft);
	}

	template <unsigned int Salt, unsigned int Indx>
	inline SaltedID<Salt, Indx> operator- (SaltedID<Salt, Indx> parLeft, typename SaltedID<Salt, Indx>::index_type parRight) {
		return (parLeft -= parRight);
	}

	template <unsigned int Salt, unsigned int Indx>
	inline SaltedID<Salt, Indx> operator- (typename SaltedID<Salt, Indx>::index_type parLeft, SaltedID<Salt, Indx> parRight) {
		return (parRight -= parLeft);
	}
} //namespace dk

#endif