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| 1 | //===-- A self contained equivalent of std::bitset --------------*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_BITSET_H |
| 10 | #define LLVM_LIBC_SRC___SUPPORT_CPP_BITSET_H |
| 11 | |
| 12 | #include "src/__support/macros/attributes.h" |
| 13 | #include "src/__support/macros/config.h" |
| 14 | #include <stddef.h> // For size_t. |
| 15 | |
| 16 | namespace LIBC_NAMESPACE_DECL { |
| 17 | namespace cpp { |
| 18 | |
| 19 | template <size_t NumberOfBits> struct bitset { |
| 20 | static_assert(NumberOfBits != 0, |
| 21 | "Cannot create a LIBC_NAMESPACE::cpp::bitset of size 0."); |
| 22 | |
| 23 | LIBC_INLINE constexpr void set(size_t Index) { |
| 24 | Data[Index / BITS_PER_UNIT] |= mask(Index); |
| 25 | } |
| 26 | |
| 27 | LIBC_INLINE constexpr void reset() { |
| 28 | for (size_t i = 0; i < NUMBER_OF_UNITS; ++i) |
| 29 | Data[i] = 0; |
| 30 | } |
| 31 | |
| 32 | LIBC_INLINE constexpr bool test(size_t Index) const { |
| 33 | return Data[Index / BITS_PER_UNIT] & mask(Index); |
| 34 | } |
| 35 | |
| 36 | LIBC_INLINE constexpr void flip() { |
| 37 | for (size_t i = 0; i < NUMBER_OF_UNITS; ++i) |
| 38 | Data[i] = ~Data[i]; |
| 39 | } |
| 40 | |
| 41 | // This function sets all bits in the range from Start to End (inclusive) to |
| 42 | // true. It assumes that Start <= End. |
| 43 | LIBC_INLINE constexpr void set_range(size_t Start, size_t End) { |
| 44 | size_t start_index = Start / BITS_PER_UNIT; |
| 45 | size_t end_index = End / BITS_PER_UNIT; |
| 46 | |
| 47 | if (start_index == end_index) { |
| 48 | // The reason the left shift is split into two parts (instead of just left |
| 49 | // shifting by End - Start + 1) is because when a number is shifted left |
| 50 | // by 64 then it wraps around to doing nothing, but shifting by 63 and the |
| 51 | // shifting by 1 correctly shifts away all of the bits. |
| 52 | size_t bit_mask = (((size_t(1) << (End - Start)) << 1) - 1) |
| 53 | << (Start - (start_index * BITS_PER_UNIT)); |
| 54 | Data[start_index] |= bit_mask; |
| 55 | } else { |
| 56 | size_t low_bit_mask = |
| 57 | ~((size_t(1) << (Start - (start_index * BITS_PER_UNIT))) - 1); |
| 58 | Data[start_index] |= low_bit_mask; |
| 59 | |
| 60 | for (size_t i = start_index + 1; i < end_index; ++i) |
| 61 | Data[i] = ~size_t(0); |
| 62 | |
| 63 | // Same as above, by splitting the shift the behavior is more consistent. |
| 64 | size_t high_bit_mask = |
| 65 | ((size_t(1) << (End - (end_index * BITS_PER_UNIT))) << 1) - 1; |
| 66 | Data[end_index] |= high_bit_mask; |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | LIBC_INLINE constexpr bool |
| 71 | operator==(const bitset<NumberOfBits> &other) const { |
| 72 | for (size_t i = 0; i < NUMBER_OF_UNITS; ++i) { |
| 73 | if (Data[i] != other.Data[i]) |
| 74 | return false; |
| 75 | } |
| 76 | return true; |
| 77 | } |
| 78 | |
| 79 | private: |
| 80 | static constexpr size_t BITS_PER_BYTE = 8; |
| 81 | static constexpr size_t BITS_PER_UNIT = BITS_PER_BYTE * sizeof(size_t); |
| 82 | static constexpr size_t NUMBER_OF_UNITS = |
| 83 | (NumberOfBits + BITS_PER_UNIT - 1) / BITS_PER_UNIT; |
| 84 | |
| 85 | LIBC_INLINE static constexpr size_t mask(size_t Index) { |
| 86 | return size_t{1} << (Index % BITS_PER_UNIT); |
| 87 | } |
| 88 | size_t Data[NUMBER_OF_UNITS] = {0}; |
| 89 | }; |
| 90 | |
| 91 | } // namespace cpp |
| 92 | } // namespace LIBC_NAMESPACE_DECL |
| 93 | |
| 94 | #endif // LLVM_LIBC_SRC___SUPPORT_CPP_BITSET_H |
| 95 |
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