Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 1 | // Copyright 2017 The Chromium Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef COMPONENTS_ZUCCHINI_ALGORITHM_H_ |
| 6 | #define COMPONENTS_ZUCCHINI_ALGORITHM_H_ |
| 7 | |
| 8 | #include <stddef.h> |
| 9 | |
| 10 | #include <algorithm> |
Etienne Pierre-doray | aff4086 | 2021-09-14 17:31:51 +0000 | [diff] [blame] | 11 | #include <deque> |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 12 | #include <type_traits> |
| 13 | #include <vector> |
| 14 | |
Hans Wennborg | d5ccca8 | 2020-06-24 13:46:35 +0000 | [diff] [blame] | 15 | #include "base/check_op.h" |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 16 | |
| 17 | // Collection of simple utilities used in for low-level computation. |
| 18 | |
| 19 | namespace zucchini { |
| 20 | |
| 21 | // Safely determines whether |[begin, begin + size)| is in |[0, bound)|. Note: |
| 22 | // The special case |[bound, bound)| is not considered to be in |[0, bound)|. |
| 23 | template <typename T> |
| 24 | bool RangeIsBounded(T begin, T size, size_t bound) { |
| 25 | static_assert(std::is_unsigned<T>::value, "Value type must be unsigned."); |
| 26 | return begin < bound && size <= bound - begin; |
| 27 | } |
| 28 | |
| 29 | // Safely determines whether |value| lies in |[begin, begin + size)|. Works |
| 30 | // properly even if |begin + size| overflows -- although such ranges are |
| 31 | // considered pathological, and should fail validation elsewhere. |
| 32 | template <typename T> |
| 33 | bool RangeCovers(T begin, T size, T value) { |
| 34 | static_assert(std::is_unsigned<T>::value, "Value type must be unsigned."); |
| 35 | return begin <= value && value - begin < size; |
| 36 | } |
| 37 | |
| 38 | // Returns the integer in inclusive range |[lo, hi]| that's closest to |value|. |
| 39 | // This departs from the usual usage of semi-inclusive ranges, but is useful |
| 40 | // because (1) sentinels can use this, (2) a valid output always exists. It is |
| 41 | // assumed that |lo <= hi|. |
| 42 | template <class T> |
| 43 | T InclusiveClamp(T value, T lo, T hi) { |
| 44 | static_assert(std::is_unsigned<T>::value, "Value type must be unsigned."); |
| 45 | DCHECK_LE(lo, hi); |
| 46 | return value <= lo ? lo : (value >= hi ? hi : value); |
| 47 | } |
| 48 | |
| 49 | // Returns the minimum multiple of |m| that's no less than |x|. Assumes |m > 0| |
| 50 | // and |x| is sufficiently small so that no overflow occurs. |
| 51 | template <class T> |
Samuel Huang | 607ce60 | 2018-06-13 17:47:39 +0000 | [diff] [blame] | 52 | constexpr T AlignCeil(T x, T m) { |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 53 | static_assert(std::is_unsigned<T>::value, "Value type must be unsigned."); |
| 54 | return T((x + m - 1) / m) * m; |
| 55 | } |
| 56 | |
Samuel Huang | 156a6f2 | 2019-03-15 21:08:23 +0000 | [diff] [blame] | 57 | // Specialized alignment helpers that returns the increment to |pos| to get the |
| 58 | // next n-aligned value, where n is in {2, 4}. This is useful for aligning |
| 59 | // iterators relative to a base iterator using: |
| 60 | // it += IncrementForAlignCeil2(it - base); |
| 61 | template <class T> |
| 62 | inline int IncrementForAlignCeil2(T pos) { |
| 63 | return static_cast<int>(pos & 1); // Optimized from (-pos) & 1. |
| 64 | } |
| 65 | |
| 66 | template <class T> |
| 67 | inline int IncrementForAlignCeil4(T pos) { |
| 68 | return static_cast<int>((-pos) & 3); |
| 69 | } |
| 70 | |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 71 | // Sorts values in |container| and removes duplicates. |
| 72 | template <class T> |
Etienne Pierre-doray | aff4086 | 2021-09-14 17:31:51 +0000 | [diff] [blame] | 73 | void SortAndUniquify(std::deque<T>* container) { |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 74 | std::sort(container->begin(), container->end()); |
| 75 | container->erase(std::unique(container->begin(), container->end()), |
| 76 | container->end()); |
| 77 | container->shrink_to_fit(); |
| 78 | } |
| 79 | |
Samuel Huang | 607ce60 | 2018-06-13 17:47:39 +0000 | [diff] [blame] | 80 | // Extracts a single bit at |pos| from integer |v|. |
| 81 | template <int pos, typename T> |
| 82 | constexpr T GetBit(T v) { |
| 83 | return (v >> pos) & 1; |
| 84 | } |
| 85 | |
| 86 | // Extracts bits in inclusive range [|lo|, |hi|] from integer |v|, and returns |
| 87 | // the sign-extend result. For example, let the (MSB-first) bits in a 32-bit int |
| 88 | // |v| be: |
| 89 | // xxxxxxxx xxxxxSii iiiiiiii iyyyyyyy, |
| 90 | // hi^ lo^ => lo = 7, hi = 18 |
| 91 | // To extract "Sii iiiiiiii i", calling |
| 92 | // GetSignedBits<7, 18>(v); |
| 93 | // produces the sign-extended result: |
| 94 | // SSSSSSSS SSSSSSSS SSSSSiii iiiiiiii. |
| 95 | template <int lo, int hi, typename T> |
| 96 | constexpr typename std::make_signed<T>::type GetSignedBits(T v) { |
| 97 | constexpr int kNumBits = sizeof(T) * 8; |
| 98 | using SignedType = typename std::make_signed<T>::type; |
| 99 | // Assumes 0 <= |lo| <= |hi| < |kNumBits|. |
| 100 | // How this works: |
| 101 | // (1) Shift-left by |kNumBits - 1 - hi| to clear "left" bits. |
| 102 | // (2) Shift-right by |kNumBits - 1 - hi + lo| to clear "right" bits. The |
| 103 | // input is casted to a signed type to perform sign-extension. |
| 104 | return static_cast<SignedType>(v << (kNumBits - 1 - hi)) >> |
| 105 | (kNumBits - 1 - hi + lo); |
| 106 | } |
| 107 | |
| 108 | // Similar to GetSignedBits(), but returns the zero-extended result. For the |
| 109 | // above example, calling |
| 110 | // GetUnsignedBits<7, 18>(v); |
| 111 | // results in: |
| 112 | // 00000000 00000000 0000Siii iiiiiiii. |
| 113 | template <int lo, int hi, typename T> |
| 114 | constexpr typename std::make_unsigned<T>::type GetUnsignedBits(T v) { |
| 115 | constexpr int kNumBits = sizeof(T) * 8; |
| 116 | using UnsignedType = typename std::make_unsigned<T>::type; |
| 117 | return static_cast<UnsignedType>(v << (kNumBits - 1 - hi)) >> |
| 118 | (kNumBits - 1 - hi + lo); |
| 119 | } |
| 120 | |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 121 | // Copies bits at |pos| in |v| to all higher bits, and returns the result as the |
| 122 | // same int type as |v|. |
| 123 | template <typename T> |
| 124 | constexpr T SignExtend(int pos, T v) { |
| 125 | int kNumBits = sizeof(T) * 8; |
| 126 | int kShift = kNumBits - 1 - pos; |
| 127 | return static_cast<typename std::make_signed<T>::type>(v << kShift) >> kShift; |
| 128 | } |
| 129 | |
| 130 | // Optimized version where |pos| becomes a template parameter. |
| 131 | template <int pos, typename T> |
| 132 | constexpr T SignExtend(T v) { |
| 133 | constexpr int kNumBits = sizeof(T) * 8; |
| 134 | constexpr int kShift = kNumBits - 1 - pos; |
| 135 | return static_cast<typename std::make_signed<T>::type>(v << kShift) >> kShift; |
| 136 | } |
| 137 | |
Samuel Huang | 607ce60 | 2018-06-13 17:47:39 +0000 | [diff] [blame] | 138 | // Determines whether |v|, if interpreted as a signed integer, is representable |
| 139 | // using |digs| bits. |1 <= digs <= sizeof(T)| is assumed. |
| 140 | template <int digs, typename T> |
| 141 | constexpr bool SignedFit(T v) { |
| 142 | return v == SignExtend<digs - 1, T>(v); |
| 143 | } |
| 144 | |
Samuel Huang | 06f1ae9 | 2018-03-13 18:19:34 +0000 | [diff] [blame] | 145 | } // namespace zucchini |
| 146 | |
| 147 | #endif // COMPONENTS_ZUCCHINI_ALGORITHM_H_ |