/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- * vim: set ts=8 sts=4 et sw=4 tw=99: * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ #ifndef ds_BitArray_h #define ds_BitArray_h #include "mozilla/TemplateLib.h" #include <limits.h> #include "jstypes.h" namespace js { template <size_t nbits> class BitArray { private: // Use a 32 bit word to make it easier to access a BitArray from JIT code. using WordT = uint32_t; static const size_t bitsPerElement = sizeof(WordT) * CHAR_BIT; static const size_t numSlots = nbits / bitsPerElement + (nbits % bitsPerElement == 0 ? 0 : 1); static const size_t paddingBits = (numSlots * bitsPerElement) - nbits; static_assert(paddingBits < bitsPerElement, "More padding bits than expected."); static const WordT paddingMask = WordT(-1) >> paddingBits; WordT map[numSlots]; public: void clear(bool value) { memset(map, value ? 0xFF : 0, sizeof(map)); if (value) map[numSlots - 1] &= paddingMask; } inline bool get(size_t offset) const { size_t index; WordT mask; getIndexAndMask(offset, &index, &mask); return map[index] & mask; } void set(size_t offset) { size_t index; WordT mask; getIndexAndMask(offset, &index, &mask); map[index] |= mask; } void unset(size_t offset) { size_t index; WordT mask; getIndexAndMask(offset, &index, &mask); map[index] &= ~mask; } bool isAllClear() const { for (size_t i = 0; i < numSlots; i++) { if (map[i]) return false; } return true; } static void getIndexAndMask(size_t offset, size_t* indexp, WordT* maskp) { static_assert(bitsPerElement == 32, "unexpected bitsPerElement value"); *indexp = offset / bitsPerElement; *maskp = WordT(1) << (offset % bitsPerElement); } static size_t offsetOfMap() { return offsetof(BitArray<nbits>, map); } }; } /* namespace js */ #endif /* ds_BitArray_h */