1 //===-- Memory Size ---------------------------------------------*- 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_MEMORY_SIZE_H
10 #define LLVM_LIBC_SRC___SUPPORT_MEMORY_SIZE_H
11
12 #include "src/__support/CPP/bit.h" // has_single_bit
13 #include "src/__support/CPP/limits.h"
14 #include "src/__support/CPP/type_traits.h"
15 #include "src/__support/macros/attributes.h"
16 #include "src/__support/macros/optimization.h"
17 #include "src/string/memory_utils/utils.h"
18
19 namespace LIBC_NAMESPACE {
20 namespace internal {
mul_overflow(T a,T b,T * res)21 template <class T> LIBC_INLINE bool mul_overflow(T a, T b, T *res) {
22 #if __has_builtin(__builtin_mul_overflow)
23 return __builtin_mul_overflow(a, b, res);
24 #else
25 T max = cpp::numeric_limits<T>::max();
26 T min = cpp::numeric_limits<T>::min();
27 bool overflow = (b > 0 && (a > max / b || a < min / b)) ||
28 (b < 0 && (a < max / b || a > min / b));
29 if (!overflow)
30 *res = a * b;
31 return overflow;
32 #endif
33 }
34 // Limit memory size to the max of ssize_t
35 class SafeMemSize {
36 private:
37 using type = cpp::make_signed_t<size_t>;
38 type value;
SafeMemSize(type value)39 LIBC_INLINE explicit SafeMemSize(type value) : value(value) {}
40
41 public:
42 LIBC_INLINE_VAR static constexpr size_t MAX_MEM_SIZE =
43 static_cast<size_t>(cpp::numeric_limits<type>::max());
44
SafeMemSize(size_t value)45 LIBC_INLINE explicit SafeMemSize(size_t value)
46 : value(value <= MAX_MEM_SIZE ? static_cast<type>(value) : -1) {}
47
offset_to(size_t val,size_t align)48 LIBC_INLINE static constexpr size_t offset_to(size_t val, size_t align) {
49 return (-val) & (align - 1);
50 }
51
size_t()52 LIBC_INLINE operator size_t() { return static_cast<size_t>(value); }
53
valid()54 LIBC_INLINE bool valid() { return value >= 0; }
55
56 LIBC_INLINE SafeMemSize operator+(const SafeMemSize &other) {
57 type result;
58 if (LIBC_UNLIKELY((value | other.value) < 0)) {
59 result = -1;
60 } else {
61 result = value + other.value;
62 }
63 return SafeMemSize{result};
64 }
65
66 LIBC_INLINE SafeMemSize operator*(const SafeMemSize &other) {
67 type result;
68 if (LIBC_UNLIKELY((value | other.value) < 0))
69 result = -1;
70 if (LIBC_UNLIKELY(mul_overflow(value, other.value, &result)))
71 result = -1;
72 return SafeMemSize{result};
73 }
74
align_up(size_t alignment)75 LIBC_INLINE SafeMemSize align_up(size_t alignment) {
76 if (!cpp::has_single_bit(alignment) || alignment > MAX_MEM_SIZE || !valid())
77 return SafeMemSize{type{-1}};
78
79 type offset = offset_to(value, alignment);
80
81 if (LIBC_UNLIKELY(offset > static_cast<type>(MAX_MEM_SIZE) - value))
82 return SafeMemSize{type{-1}};
83
84 return SafeMemSize{value + offset};
85 }
86 };
87 } // namespace internal
88 } // namespace LIBC_NAMESPACE
89
90 #endif // LLVM_LIBC_SRC___SUPPORT_MEMORY_SIZE_H
91