1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
|
// Copyright 2017 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
#define BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
#include <stddef.h>
#include <stdint.h>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdlib>
#include <limits>
#include <type_traits>
#include "base/numerics/safe_conversions.h"
#ifdef __asmjs__
// Optimized safe math instructions are incompatible with asmjs.
#define BASE_HAS_OPTIMIZED_SAFE_MATH (0)
// Where available use builtin math overflow support on Clang and GCC.
#elif !defined(__native_client__) && \
((defined(__clang__) && \
((__clang_major__ > 3) || \
(__clang_major__ == 3 && __clang_minor__ >= 4))) || \
(defined(__GNUC__) && __GNUC__ >= 5))
#include "base/numerics/safe_math_clang_gcc_impl.h"
#define BASE_HAS_OPTIMIZED_SAFE_MATH (1)
#else
#define BASE_HAS_OPTIMIZED_SAFE_MATH (0)
#endif
namespace base {
namespace internal {
// These are the non-functioning boilerplate implementations of the optimized
// safe math routines.
#if !BASE_HAS_OPTIMIZED_SAFE_MATH
template <typename T, typename U>
struct CheckedAddFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr bool Do(T, U, V*) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<bool>();
}
};
template <typename T, typename U>
struct CheckedSubFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr bool Do(T, U, V*) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<bool>();
}
};
template <typename T, typename U>
struct CheckedMulFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr bool Do(T, U, V*) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<bool>();
}
};
template <typename T, typename U>
struct ClampedAddFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr V Do(T, U) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<V>();
}
};
template <typename T, typename U>
struct ClampedSubFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr V Do(T, U) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<V>();
}
};
template <typename T, typename U>
struct ClampedMulFastOp {
static const bool is_supported = false;
template <typename V>
static constexpr V Do(T, U) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<V>();
}
};
template <typename T>
struct ClampedNegFastOp {
static const bool is_supported = false;
static constexpr T Do(T) {
// Force a compile failure if instantiated.
return CheckOnFailure::template HandleFailure<T>();
}
};
#endif // BASE_HAS_OPTIMIZED_SAFE_MATH
#undef BASE_HAS_OPTIMIZED_SAFE_MATH
// This is used for UnsignedAbs, where we need to support floating-point
// template instantiations even though we don't actually support the operations.
// However, there is no corresponding implementation of e.g. SafeUnsignedAbs,
// so the float versions will not compile.
template <typename Numeric,
bool IsInteger = std::is_integral<Numeric>::value,
bool IsFloat = std::is_floating_point<Numeric>::value>
struct UnsignedOrFloatForSize;
template <typename Numeric>
struct UnsignedOrFloatForSize<Numeric, true, false> {
using type = typename std::make_unsigned<Numeric>::type;
};
template <typename Numeric>
struct UnsignedOrFloatForSize<Numeric, false, true> {
using type = Numeric;
};
// Wrap the unary operations to allow SFINAE when instantiating integrals versus
// floating points. These don't perform any overflow checking. Rather, they
// exhibit well-defined overflow semantics and rely on the caller to detect
// if an overflow occured.
template <typename T,
typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
constexpr T NegateWrapper(T value) {
using UnsignedT = typename std::make_unsigned<T>::type;
// This will compile to a NEG on Intel, and is normal negation on ARM.
return static_cast<T>(UnsignedT(0) - static_cast<UnsignedT>(value));
}
template <
typename T,
typename std::enable_if<std::is_floating_point<T>::value>::type* = nullptr>
constexpr T NegateWrapper(T value) {
return -value;
}
template <typename T,
typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
constexpr typename std::make_unsigned<T>::type InvertWrapper(T value) {
return ~value;
}
template <typename T,
typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
constexpr T AbsWrapper(T value) {
return static_cast<T>(SafeUnsignedAbs(value));
}
template <
typename T,
typename std::enable_if<std::is_floating_point<T>::value>::type* = nullptr>
constexpr T AbsWrapper(T value) {
return value < 0 ? -value : value;
}
template <template <typename, typename, typename> class M,
typename L,
typename R>
struct MathWrapper {
using math = M<typename UnderlyingType<L>::type,
typename UnderlyingType<R>::type,
void>;
using type = typename math::result_type;
};
// These variadic templates work out the return types.
// TODO(jschuh): Rip all this out once we have C++14 non-trailing auto support.
template <template <typename, typename, typename> class M,
typename L,
typename R,
typename... Args>
struct ResultType;
template <template <typename, typename, typename> class M,
typename L,
typename R>
struct ResultType<M, L, R> {
using type = typename MathWrapper<M, L, R>::type;
};
template <template <typename, typename, typename> class M,
typename L,
typename R,
typename... Args>
struct ResultType {
using type =
typename ResultType<M, typename ResultType<M, L, R>::type, Args...>::type;
};
// The following macros are just boilerplate for the standard arithmetic
// operator overloads and variadic function templates. A macro isn't the nicest
// solution, but it beats rewriting these over and over again.
#define BASE_NUMERIC_ARITHMETIC_VARIADIC(CLASS, CL_ABBR, OP_NAME) \
template <typename L, typename R, typename... Args> \
constexpr CLASS##Numeric< \
typename ResultType<CLASS##OP_NAME##Op, L, R, Args...>::type> \
CL_ABBR##OP_NAME(const L lhs, const R rhs, const Args... args) { \
return CL_ABBR##MathOp<CLASS##OP_NAME##Op, L, R, Args...>(lhs, rhs, \
args...); \
}
#define BASE_NUMERIC_ARITHMETIC_OPERATORS(CLASS, CL_ABBR, OP_NAME, OP, CMP_OP) \
/* Binary arithmetic operator for all CLASS##Numeric operations. */ \
template <typename L, typename R, \
typename std::enable_if<Is##CLASS##Op<L, R>::value>::type* = \
nullptr> \
constexpr CLASS##Numeric< \
typename MathWrapper<CLASS##OP_NAME##Op, L, R>::type> \
operator OP(const L lhs, const R rhs) { \
return decltype(lhs OP rhs)::template MathOp<CLASS##OP_NAME##Op>(lhs, \
rhs); \
} \
/* Assignment arithmetic operator implementation from CLASS##Numeric. */ \
template <typename L> \
template <typename R> \
constexpr CLASS##Numeric<L>& CLASS##Numeric<L>::operator CMP_OP( \
const R rhs) { \
return MathOp<CLASS##OP_NAME##Op>(rhs); \
} \
/* Variadic arithmetic functions that return CLASS##Numeric. */ \
BASE_NUMERIC_ARITHMETIC_VARIADIC(CLASS, CL_ABBR, OP_NAME)
} // namespace internal
} // namespace base
#endif // BASE_NUMERICS_SAFE_MATH_SHARED_IMPL_H_
|
