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Diffstat (limited to 'chilbert/BitVecMask.hpp')
-rw-r--r-- | chilbert/BitVecMask.hpp | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/chilbert/BitVecMask.hpp b/chilbert/BitVecMask.hpp new file mode 100644 index 0000000..af98894 --- /dev/null +++ b/chilbert/BitVecMask.hpp @@ -0,0 +1,72 @@ +/* + Copyright (C) 2018 David Robillard <d@drobilla.net> + Copyright (C) 2006-2007 Chris Hamilton <chamilton@cs.dal.ca> + + This program 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 2 of the License, or (at your option) any later + version. + + This program 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 + this program. If not, see <https://www.gnu.org/licenses/>. +*/ + +#ifndef CHILBERT_BITVECMASK_HPP +#define CHILBERT_BITVECMASK_HPP + +#include <climits> +#include <cstddef> + +namespace chilbert { + +/** Mask for a bit that can be incremented like an index. + * + * This enables fast iteration while setting or resetting bits since it is + * internally stored as a mask which avoids repeated index math. + */ +template <class Rack> +struct BitVecMask +{ + static constexpr size_t bits_per_rack = sizeof(Rack) * CHAR_BIT; + + BitVecMask(const size_t index) + : rack{index / bits_per_rack} + , mask{Rack{1} << (index - rack * bits_per_rack)} + { + } + + void operator++() + { + if ((mask <<= 1) == 0) { + mask = 1; + ++rack; + } + } + + void operator--() + { + if ((mask >>= 1) == 0) { + mask = Rack{1} << (bits_per_rack - 1); + --rack; + } + } + + bool operator==(const BitVecMask& rhs) const + { + return rack == rhs.rack && mask == rhs.mask; + } + + bool operator!=(const BitVecMask& rhs) const { return !operator==(rhs); } + + size_t rack; + Rack mask; +}; + +} // namespace chilbert + +#endif |