src/cpp-common/bt2c/safe-ops.hpp

   1 /*
   2  * Copyright (c) 2022 Philippe Proulx <pproulx@efficios.com>
   3  *
   4  * SPDX-License-Identifier: MIT
   5  */
   6
   7 #ifndef BABELTRACE_CPP_COMMON_BT2C_SAFE_OPS_HPP
   8 #define BABELTRACE_CPP_COMMON_BT2C_SAFE_OPS_HPP
   9
  10 #include <limits>
  11 #include <type_traits>
  12
  13 #include "common/assert.h"
  14
  15 namespace bt2c {
  16
  17 template <typename T>
  18 constexpr bool safeToMul(const T a, const T b)
  19 {
  20     static_assert(std::is_unsigned<T>::value, "`T` is an unsigned type.");
  21
  22     return a == 0 || b == 0 || a < std::numeric_limits<T>::max() / b;
  23 }
  24
  25 template <typename T>
  26 T safeMul(const T a, const T b) noexcept
  27 {
  28     static_assert(std::is_unsigned<T>::value, "`T` is an unsigned type.");
  29
  30     BT_ASSERT_DBG(safeToMul(a, b));
  31     return a * b;
  32 }
  33
  34 template <typename T>
  35 constexpr bool safeToAdd(const T a, const T b)
  36 {
  37     static_assert(std::is_unsigned<T>::value, "`T` is an unsigned type.");
  38
  39     return a <= std::numeric_limits<T>::max() - b;
  40 }
  41
  42 template <typename T>
  43 T safeAdd(const T a, const T b) noexcept
  44 {
  45     static_assert(std::is_unsigned<T>::value, "`T` is an unsigned type.");
  46
  47     BT_ASSERT_DBG(safeToAdd(a, b));
  48     return a + b;
  49 }
  50
  51 template <typename T>
  52 constexpr bool safeToSub(const T a, const T b)
  53 {
  54     static_assert(std::is_unsigned<T>::value, "`T` is an unsigned type.");
  55
  56     return a >= b;
  57 }
  58
  59 template <typename T>
  60 T safeSub(const T a, const T b) noexcept
  61 {
  62     static_assert(std::is_unsigned<T>::value, "`T` is an unsigned type.");
  63
  64     BT_ASSERT_DBG(safeToSub(a, b));
  65     return a - b;
  66 }
  67
  68 } /* namespace bt2c */
  69
  70 #endif /* BABELTRACE_CPP_COMMON_BT2C_SAFE_OPS_HPP */