include/o3tl/intcmp.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #pragma once
  11
  12 #include <sal/config.h>
  13
  14 #include <type_traits>
  15 #include <utility>
  16
  17 #include <o3tl/safeint.hxx>
  18
  19 namespace o3tl
  20 {
  21 // An approximation of the C++20 integer comparison functions
  22 // (<https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p0586r2.html> "Safe integral
  23 // comparisons"), still missing from LLVM 12 libc++:
  24 #if defined __cpp_lib_integer_comparison_functions
  25
  26 using std::cmp_equal;
  27 using std::cmp_not_equal;
  28 using std::cmp_less;
  29 using std::cmp_greater;
  30 using std::cmp_less_equal;
  31 using std::cmp_greater_equal;
  32
  33 #else
  34
  35 template <typename T1, typename T2> constexpr bool cmp_equal(T1 value1, T2 value2) noexcept
  36 {
  37     // coverity[same_on_both_sides: FALSE]
  38     if constexpr (std::is_signed_v<T1> == std::is_signed_v<T2>)
  39     {
  40         return value1 == value2;
  41     }
  42     else if constexpr (std::is_signed_v<T1>)
  43     {
  44         return value1 >= 0 && o3tl::make_unsigned(value1) == value2;
  45     }
  46     else
  47     {
  48         return value2 >= 0 && value1 == o3tl::make_unsigned(value2);
  49     }
  50 }
  51
  52 template <typename T1, typename T2> constexpr bool cmp_not_equal(T1 value1, T2 value2) noexcept
  53 {
  54     return !cmp_equal(value1, value2);
  55 }
  56
  57 template <typename T1, typename T2> constexpr bool cmp_less(T1 value1, T2 value2) noexcept
  58 {
  59     if constexpr (std::is_signed_v<T1> == std::is_signed_v<T2>)
  60     {
  61         return value1 < value2;
  62     }
  63     else if constexpr (std::is_signed_v<T1>)
  64     {
  65         return value1 < 0 || o3tl::make_unsigned(value1) < value2;
  66     }
  67     else
  68     {
  69         return value2 >= 0 && value1 < o3tl::make_unsigned(value2);
  70     }
  71 }
  72
  73 template <typename T1, typename T2> constexpr bool cmp_greater(T1 value1, T2 value2) noexcept
  74 {
  75     return cmp_less(value2, value1);
  76 }
  77
  78 template <typename T1, typename T2> constexpr bool cmp_less_equal(T1 value1, T2 value2) noexcept
  79 {
  80     return !cmp_greater(value1, value2);
  81 }
  82
  83 template <typename T1, typename T2> constexpr bool cmp_greater_equal(T1 value1, T2 value2) noexcept
  84 {
  85     return !cmp_less(value1, value2);
  86 }
  87
  88 #endif
  89
  90 // A convenient operator syntax around the standard integer comparison functions:
  91 template <typename T> struct IntCmp
  92 {
  93     explicit constexpr IntCmp(T theValue)
  94         : value(theValue)
  95     {
  96     }
  97
  98     T value;
  99 };
 100
 101 template <typename T1, typename T2> constexpr bool operator==(IntCmp<T1> value1, IntCmp<T2> value2)
 102 {
 103     return o3tl::cmp_equal(value1.value, value2.value);
 104 }
 105
 106 template <typename T1, typename T2> constexpr bool operator!=(IntCmp<T1> value1, IntCmp<T2> value2)
 107 {
 108     return o3tl::cmp_not_equal(value1.value, value2.value);
 109 }
 110
 111 template <typename T1, typename T2> constexpr bool operator<(IntCmp<T1> value1, IntCmp<T2> value2)
 112 {
 113     return o3tl::cmp_less(value1.value, value2.value);
 114 }
 115
 116 template <typename T1, typename T2> constexpr bool operator>(IntCmp<T1> value1, IntCmp<T2> value2)
 117 {
 118     return o3tl::cmp_greater(value1.value, value2.value);
 119 }
 120
 121 template <typename T1, typename T2> constexpr bool operator<=(IntCmp<T1> value1, IntCmp<T2> value2)
 122 {
 123     return o3tl::cmp_less_equal(value1.value, value2.value);
 124 }
 125
 126 template <typename T1, typename T2> constexpr bool operator>=(IntCmp<T1> value1, IntCmp<T2> value2)
 127 {
 128     return o3tl::cmp_greater_equal(value1.value, value2.value);
 129 }
 130 }
 131
 132 /* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */