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| 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 BASE_NUMERICS_CLAMPED_MATH_IMPL_H_ |
| 6 #define BASE_NUMERICS_CLAMPED_MATH_IMPL_H_ |
| 7 |
| 8 #include <stddef.h> |
| 9 #include <stdint.h> |
| 10 |
| 11 #include <climits> |
| 12 #include <cmath> |
| 13 #include <cstdlib> |
| 14 #include <limits> |
| 15 #include <type_traits> |
| 16 |
| 17 #include "base/numerics/checked_math.h" |
| 18 #include "base/numerics/safe_conversions.h" |
| 19 #include "base/numerics/safe_math_shared_impl.h" |
| 20 |
| 21 namespace base { |
| 22 namespace internal { |
| 23 |
| 24 // This provides a small optimization that generates more compact code when one |
| 25 // of the components in an operation is a compile-time constant. |
| 26 template <typename T> |
| 27 constexpr bool IsValueConstantAndNegative(const T v) { |
| 28 #if defined(__clang__) || defined(__GNUC__) |
| 29 return __builtin_constant_p(v) ? IsValueNegative(v) : false; |
| 30 #else |
| 31 return false; |
| 32 #endif |
| 33 } |
| 34 |
| 35 template <typename T, typename U, class Enable = void> |
| 36 struct ClampedAddOp {}; |
| 37 |
| 38 template <typename T, typename U> |
| 39 struct ClampedAddOp<T, |
| 40 U, |
| 41 typename std::enable_if<std::is_integral<T>::value && |
| 42 std::is_integral<U>::value>::type> { |
| 43 using result_type = typename MaxExponentPromotion<T, U>::type; |
| 44 template <typename V = result_type> |
| 45 static V Do(T x, U y) { |
| 46 V result; |
| 47 return CheckedAddOp<T, U>::Do(x, y, &result) |
| 48 ? result |
| 49 : (as_unsigned(std::numeric_limits<V>::max()) + |
| 50 (IsValueConstantAndNegative(x) || IsValueNegative(y))); |
| 51 } |
| 52 }; |
| 53 |
| 54 template <typename T, typename U, class Enable = void> |
| 55 struct ClampedSubOp {}; |
| 56 |
| 57 template <typename T, typename U> |
| 58 struct ClampedSubOp<T, |
| 59 U, |
| 60 typename std::enable_if<std::is_integral<T>::value && |
| 61 std::is_integral<U>::value>::type> { |
| 62 using result_type = typename MaxExponentPromotion<T, U>::type; |
| 63 template <typename V = result_type> |
| 64 static V Do(T x, U y) { |
| 65 V result; |
| 66 return CheckedSubOp<T, U>::Do(x, y, &result) |
| 67 ? result |
| 68 : (as_unsigned(std::numeric_limits<V>::max()) + |
| 69 (IsValueConstantAndNegative(x) || !IsValueNegative(y))); |
| 70 } |
| 71 }; |
| 72 |
| 73 template <typename T, typename U, class Enable = void> |
| 74 struct ClampedMulOp {}; |
| 75 |
| 76 template <typename T, typename U> |
| 77 struct ClampedMulOp<T, |
| 78 U, |
| 79 typename std::enable_if<std::is_integral<T>::value && |
| 80 std::is_integral<U>::value>::type> { |
| 81 using result_type = typename MaxExponentPromotion<T, U>::type; |
| 82 template <typename V = result_type> |
| 83 static V Do(T x, U y) { |
| 84 V result; |
| 85 return CheckedMulOp<T, U>::Do(x, y, &result) |
| 86 ? result |
| 87 : as_unsigned(std::numeric_limits<V>::max()) + |
| 88 (IsValueNegative(x) ^ IsValueNegative(y)); |
| 89 } |
| 90 }; |
| 91 |
| 92 template <typename T, typename U, class Enable = void> |
| 93 struct ClampedDivOp {}; |
| 94 |
| 95 template <typename T, typename U> |
| 96 struct ClampedDivOp<T, |
| 97 U, |
| 98 typename std::enable_if<std::is_integral<T>::value && |
| 99 std::is_integral<U>::value>::type> { |
| 100 using result_type = typename MaxExponentPromotion<T, U>::type; |
| 101 template <typename V = result_type> |
| 102 static V Do(T x, U y) { |
| 103 V result; |
| 104 return CheckedDivOp<T, U>::Do(x, y, &result) |
| 105 ? result |
| 106 : as_unsigned(std::numeric_limits<V>::max()) + |
| 107 (IsValueNegative(x) ^ IsValueNegative(y)); |
| 108 } |
| 109 }; |
| 110 |
| 111 template <typename T, typename U, class Enable = void> |
| 112 struct ClampedModOp {}; |
| 113 |
| 114 template <typename T, typename U> |
| 115 struct ClampedModOp<T, |
| 116 U, |
| 117 typename std::enable_if<std::is_integral<T>::value && |
| 118 std::is_integral<U>::value>::type> { |
| 119 using result_type = typename MaxExponentPromotion<T, U>::type; |
| 120 template <typename V = result_type> |
| 121 static V Do(T x, U y) { |
| 122 V result; |
| 123 return CheckedModOp<T, U>::Do(x, y, &result) ? result : x; |
| 124 } |
| 125 }; |
| 126 |
| 127 template <typename T, typename U, class Enable = void> |
| 128 struct ClampedLshOp {}; |
| 129 |
| 130 // Left shift. Non-zero values saturate in the direction of the sign. A zero |
| 131 // shifted by any value always results in zero. |
| 132 // Note: This class template supports left shifting negative values. |
| 133 template <typename T, typename U> |
| 134 struct ClampedLshOp<T, |
| 135 U, |
| 136 typename std::enable_if<std::is_integral<T>::value && |
| 137 std::is_integral<U>::value>::type> { |
| 138 using result_type = T; |
| 139 template <typename V = result_type> |
| 140 static V Do(T x, U shift) { |
| 141 static_assert(!std::is_signed<U>::value, "Shift value must be unsigned."); |
| 142 V result = x; |
| 143 return CheckedLshOp<T, U>::Do(x, shift, &result) |
| 144 ? result |
| 145 : as_unsigned(std::numeric_limits<V>::max()) + |
| 146 IsValueNegative(x); |
| 147 } |
| 148 }; |
| 149 |
| 150 template <typename T, typename U, class Enable = void> |
| 151 struct ClampedRshOp {}; |
| 152 |
| 153 // Right shift. Negative values saturate to -1. Positive or 0 saturates to 0. |
| 154 template <typename T, typename U> |
| 155 struct ClampedRshOp<T, |
| 156 U, |
| 157 typename std::enable_if<std::is_integral<T>::value && |
| 158 std::is_integral<U>::value>::type> { |
| 159 using result_type = T; |
| 160 template <typename V = result_type> |
| 161 static V Do(T x, U shift) { |
| 162 static_assert(!std::is_signed<U>::value, "Shift value must be unsigned."); |
| 163 V result = x; |
| 164 return CheckedRshOp<T, U>::Do(x, shift, &result) |
| 165 ? result |
| 166 : as_unsigned(V(0)) - IsValueNegative(x); |
| 167 } |
| 168 }; |
| 169 |
| 170 template <typename T, typename U, class Enable = void> |
| 171 struct ClampedAndOp {}; |
| 172 |
| 173 template <typename T, typename U> |
| 174 struct ClampedAndOp<T, |
| 175 U, |
| 176 typename std::enable_if<std::is_integral<T>::value && |
| 177 std::is_integral<U>::value>::type> { |
| 178 using result_type = typename std::make_unsigned< |
| 179 typename MaxExponentPromotion<T, U>::type>::type; |
| 180 template <typename V> |
| 181 static constexpr V Do(T x, U y) { |
| 182 return static_cast<result_type>(x) & static_cast<result_type>(y); |
| 183 } |
| 184 }; |
| 185 |
| 186 template <typename T, typename U, class Enable = void> |
| 187 struct ClampedOrOp {}; |
| 188 |
| 189 // For simplicity we promote to unsigned integers. |
| 190 template <typename T, typename U> |
| 191 struct ClampedOrOp<T, |
| 192 U, |
| 193 typename std::enable_if<std::is_integral<T>::value && |
| 194 std::is_integral<U>::value>::type> { |
| 195 using result_type = typename std::make_unsigned< |
| 196 typename MaxExponentPromotion<T, U>::type>::type; |
| 197 template <typename V> |
| 198 static constexpr V Do(T x, U y) { |
| 199 return static_cast<result_type>(x) | static_cast<result_type>(y); |
| 200 } |
| 201 }; |
| 202 |
| 203 template <typename T, typename U, class Enable = void> |
| 204 struct ClampedXorOp {}; |
| 205 |
| 206 // For simplicity we support only unsigned integers. |
| 207 template <typename T, typename U> |
| 208 struct ClampedXorOp<T, |
| 209 U, |
| 210 typename std::enable_if<std::is_integral<T>::value && |
| 211 std::is_integral<U>::value>::type> { |
| 212 using result_type = typename std::make_unsigned< |
| 213 typename MaxExponentPromotion<T, U>::type>::type; |
| 214 template <typename V> |
| 215 static constexpr V Do(T x, U y) { |
| 216 return static_cast<result_type>(x) ^ static_cast<result_type>(y); |
| 217 } |
| 218 }; |
| 219 |
| 220 template <typename T, typename U, class Enable = void> |
| 221 struct ClampedMaxOp {}; |
| 222 |
| 223 template <typename T, typename U> |
| 224 struct ClampedMaxOp< |
| 225 T, |
| 226 U, |
| 227 typename std::enable_if<std::is_arithmetic<T>::value && |
| 228 std::is_arithmetic<U>::value>::type> { |
| 229 using result_type = typename MaxExponentPromotion<T, U>::type; |
| 230 template <typename V = result_type> |
| 231 static constexpr V Do(T x, U y) { |
| 232 return IsGreater<T, U>::Test(x, y) ? saturated_cast<V>(x) |
| 233 : saturated_cast<V>(y); |
| 234 } |
| 235 }; |
| 236 |
| 237 template <typename T, typename U, class Enable = void> |
| 238 struct ClampedMinOp {}; |
| 239 |
| 240 template <typename T, typename U> |
| 241 struct ClampedMinOp< |
| 242 T, |
| 243 U, |
| 244 typename std::enable_if<std::is_arithmetic<T>::value && |
| 245 std::is_arithmetic<U>::value>::type> { |
| 246 using result_type = typename LowestValuePromotion<T, U>::type; |
| 247 template <typename V = result_type> |
| 248 static constexpr V Do(T x, U y) { |
| 249 return IsLess<T, U>::Test(x, y) ? saturated_cast<V>(x) |
| 250 : saturated_cast<V>(y); |
| 251 } |
| 252 }; |
| 253 |
| 254 // This is just boilerplate that wraps the standard floating point arithmetic. |
| 255 // A macro isn't the nicest solution, but it beats rewriting these repeatedly. |
| 256 #define BASE_FLOAT_ARITHMETIC_OPS(NAME, OP) \ |
| 257 template <typename T, typename U> \ |
| 258 struct Clamped##NAME##Op< \ |
| 259 T, U, \ |
| 260 typename std::enable_if<std::is_floating_point<T>::value || \ |
| 261 std::is_floating_point<U>::value>::type> { \ |
| 262 using result_type = typename MaxExponentPromotion<T, U>::type; \ |
| 263 template <typename V = result_type> \ |
| 264 static constexpr V Do(T x, U y) { \ |
| 265 return saturated_cast<V>(x OP y); \ |
| 266 } \ |
| 267 }; |
| 268 |
| 269 BASE_FLOAT_ARITHMETIC_OPS(Add, +) |
| 270 BASE_FLOAT_ARITHMETIC_OPS(Sub, -) |
| 271 BASE_FLOAT_ARITHMETIC_OPS(Mul, *) |
| 272 BASE_FLOAT_ARITHMETIC_OPS(Div, /) |
| 273 |
| 274 #undef BASE_FLOAT_ARITHMETIC_OPS |
| 275 |
| 276 } // namespace internal |
| 277 } // namespace base |
| 278 |
| 279 #endif // BASE_NUMERICS_CLAMPED_MATH_IMPL_H_ |
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