kstd: introduce basic offset type

1 files changed, 45 insertions, 1 deletions

diff --git a/libs/kstd/kstd/units.hpp b/libs/kstd/kstd/units.hpp
index e3868aa7..61224336 100644
--- a/libs/kstd/kstd/units.hpp
+++ b/libs/kstd/kstd/units.hpp
@@ -2,6 +2,8 @@
 #define KSTD_UNITS_HPP
 
 #include <kstd/bits/basic_unit.hpp>
+#include <kstd/result.hpp>
+#include <kstd/system_error.hpp>
 
 #include <concepts>
 #include <cstddef>
@@ -11,6 +13,8 @@ namespace kstd
 
   using bytes = basic_unit<std::size_t, struct bytes_tag>;
 
+  using offset = basic_unit<std::ptrdiff_t, struct byte_offset_tag>;
+
   // NOLINTNEXTLINE(readability-identifier-naming)
   constexpr auto KiB(std::unsigned_integral auto value) noexcept -> bytes
   {
@@ -30,11 +34,31 @@ namespace kstd
   }
 
   template<typename ValueType>
-  constexpr auto operator+(ValueType * pointer, bytes offset) -> ValueType *
+  constexpr auto operator+(ValueType * pointer, bytes offset) noexcept -> ValueType *
   {
     return pointer + offset.value;
   }
 
+  constexpr auto operator+(bytes value, offset offset) noexcept -> result<bytes>
+  {
+    if (offset.value < 0 && value.value < static_cast<bytes::value_type>(-offset.value))
+    {
+      return failure(make_error_code(errc::argument_out_of_domain));
+    }
+    value.value += offset.value;
+    return value;
+  }
+
+  constexpr auto operator-(bytes value, offset offset) noexcept -> result<bytes>
+  {
+    if (offset.value > 0 && value.value < static_cast<bytes::value_type>(offset.value))
+    {
+      return failure(make_error_code(errc::argument_out_of_domain));
+    }
+    value.value -= offset.value;
+    return value;
+  }
+
   inline namespace literals
   {
     inline namespace units_literals
@@ -59,6 +83,26 @@ namespace kstd
         return GiB(value);
       }
 
+      constexpr auto operator""_B_off(unsigned long long value) noexcept -> offset
+      {
+        return offset{static_cast<offset::value_type>(value)};
+      }
+
+      constexpr auto operator""_KiB_off(unsigned long long value) noexcept -> offset
+      {
+        return offset{static_cast<offset::value_type>(value * 1024)};
+      }
+
+      constexpr auto operator""_MiB_off(unsigned long long value) noexcept -> offset
+      {
+        return offset{static_cast<offset::value_type>(value * 1024 * 1024)};
+      }
+
+      constexpr auto operator""_GiB_off(unsigned long long value) noexcept -> offset
+      {
+        return offset{static_cast<offset::value_type>(value * 1024 * 1024 * 1024)};
+      }
+
     }  // namespace units_literals
   }  // namespace literals