1 files changed, 132 insertions, 0 deletions
diff --git a/include/o3tl/intcmp.hxx b/include/o3tl/intcmp.hxx
new file mode 100644
index 0000000000..dbc10d9052
--- /dev/null
+++ b/include/o3tl/intcmp.hxx
@@ -0,0 +1,132 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <sal/config.h>
+
+#include <type_traits>
+#include <utility>
+
+#include <o3tl/safeint.hxx>
+
+namespace o3tl
+{
+// An approximation of the C++20 integer comparison functions
+// (<https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p0586r2.html> "Safe integral
+// comparisons"), still missing from LLVM 12 libc++:
+#if defined __cpp_lib_integer_comparison_functions
+
+using std::cmp_equal;
+using std::cmp_not_equal;
+using std::cmp_less;
+using std::cmp_greater;
+using std::cmp_less_equal;
+using std::cmp_greater_equal;
+
+#else
+
+template <typename T1, typename T2> constexpr bool cmp_equal(T1 value1, T2 value2) noexcept
+{
+    // coverity[same_on_both_sides: FALSE]
+    if constexpr (std::is_signed_v<T1> == std::is_signed_v<T2>)
+    {
+        return value1 == value2;
+    }
+    else if constexpr (std::is_signed_v<T1>)
+    {
+        return value1 >= 0 && o3tl::make_unsigned(value1) == value2;
+    }
+    else
+    {
+        return value2 >= 0 && value1 == o3tl::make_unsigned(value2);
+    }
+}
+
+template <typename T1, typename T2> constexpr bool cmp_not_equal(T1 value1, T2 value2) noexcept
+{
+    return !cmp_equal(value1, value2);
+}
+
+template <typename T1, typename T2> constexpr bool cmp_less(T1 value1, T2 value2) noexcept
+{
+    if constexpr (std::is_signed_v<T1> == std::is_signed_v<T2>)
+    {
+        return value1 < value2;
+    }
+    else if constexpr (std::is_signed_v<T1>)
+    {
+        return value1 < 0 || o3tl::make_unsigned(value1) < value2;
+    }
+    else
+    {
+        return value2 >= 0 && value1 < o3tl::make_unsigned(value2);
+    }
+}
+
+template <typename T1, typename T2> constexpr bool cmp_greater(T1 value1, T2 value2) noexcept
+{
+    return cmp_less(value2, value1);
+}
+
+template <typename T1, typename T2> constexpr bool cmp_less_equal(T1 value1, T2 value2) noexcept
+{
+    return !cmp_greater(value1, value2);
+}
+
+template <typename T1, typename T2> constexpr bool cmp_greater_equal(T1 value1, T2 value2) noexcept
+{
+    return !cmp_less(value1, value2);
+}
+
+#endif
+
+// A convenient operator syntax around the standard integer comparison functions:
+template <typename T> struct IntCmp
+{
+    explicit constexpr IntCmp(T theValue)
+        : value(theValue)
+    {
+    }
+
+    T value;
+};
+
+template <typename T1, typename T2> constexpr bool operator==(IntCmp<T1> value1, IntCmp<T2> value2)
+{
+    return o3tl::cmp_equal(value1.value, value2.value);
+}
+
+template <typename T1, typename T2> constexpr bool operator!=(IntCmp<T1> value1, IntCmp<T2> value2)
+{
+    return o3tl::cmp_not_equal(value1.value, value2.value);
+}
+
+template <typename T1, typename T2> constexpr bool operator<(IntCmp<T1> value1, IntCmp<T2> value2)
+{
+    return o3tl::cmp_less(value1.value, value2.value);
+}
+
+template <typename T1, typename T2> constexpr bool operator>(IntCmp<T1> value1, IntCmp<T2> value2)
+{
+    return o3tl::cmp_greater(value1.value, value2.value);
+}
+
+template <typename T1, typename T2> constexpr bool operator<=(IntCmp<T1> value1, IntCmp<T2> value2)
+{
+    return o3tl::cmp_less_equal(value1.value, value2.value);
+}
+
+template <typename T1, typename T2> constexpr bool operator>=(IntCmp<T1> value1, IntCmp<T2> value2)
+{
+    return o3tl::cmp_greater_equal(value1.value, value2.value);
+}
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */