From f64f51b88de9d870c8e2a8b9898a137d3f92171f Mon Sep 17 00:00:00 2001
From: Ben Deane <ben@elbeno.com>
Date: Mon, 11 Sep 2023 16:49:33 -0600
Subject: [PATCH] :sparkles: Add UDLs for useful byte sizes

---
 docs/utility.adoc        | 17 +++++++++++++++++
 include/stdx/utility.hpp | 28 ++++++++++++++++++++++++++++
 test/udls.cpp            | 14 ++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/docs/utility.adoc b/docs/utility.adoc
index 80dd9bf..39cabbe 100644
--- a/docs/utility.adoc
+++ b/docs/utility.adoc
@@ -45,3 +45,20 @@ using my_type_without_X = my_type<"X"_false>;
 using my_type_with_X_alt = my_type<"X"_b>;
 using my_type_without_X_alt = my_type<not "X"_b>;
 ----
+
+And some UDLs that are useful when specifying sizes in bytes:
+
+[source,cpp]
+----
+using namespace stdx::literals;
+
+// decimal SI prefixes
+constexpr auto a = 1_k;  // 1,000
+constexpr auto b = 1_M;  // 1,000,000
+constexpr auto c = 1_G;  // 1,000,000,000
+
+// binary equivalents
+constexpr auto d = 1_ki; // 1,024
+constexpr auto e = 1_Mi; // 1,048,567
+constexpr auto f = 1_Gi; // 1,073,741,824
+----
diff --git a/include/stdx/utility.hpp b/include/stdx/utility.hpp
index c710fb8..4e64b35 100644
--- a/include/stdx/utility.hpp
+++ b/include/stdx/utility.hpp
@@ -23,6 +23,34 @@ CONSTEVAL auto operator""_true(char const *, std::size_t) -> bool {
 CONSTEVAL auto operator""_false(char const *, std::size_t) -> bool {
     return false;
 }
+
+// NOLINTBEGIN(google-runtime-int)
+CONSTEVAL auto operator""_k(unsigned long long int n)
+    -> unsigned long long int {
+    return n * 1'000u;
+}
+CONSTEVAL auto operator""_M(unsigned long long int n)
+    -> unsigned long long int {
+    return n * 1'000'000u;
+}
+CONSTEVAL auto operator""_G(unsigned long long int n)
+    -> unsigned long long int {
+    return n * 1'000'000'000u;
+}
+
+CONSTEVAL auto operator""_ki(unsigned long long int n)
+    -> unsigned long long int {
+    return n * 1'024u;
+}
+CONSTEVAL auto operator""_Mi(unsigned long long int n)
+    -> unsigned long long int {
+    return n * 1'024ull * 1'024ull;
+}
+CONSTEVAL auto operator""_Gi(unsigned long long int n)
+    -> unsigned long long int {
+    return n * 1'024ull * 1'024ull * 1'024ull;
+}
+// NOLINTEND(google-runtime-int)
 } // namespace literals
 
 [[noreturn]] inline auto unreachable() -> void { __builtin_unreachable(); }
diff --git a/test/udls.cpp b/test/udls.cpp
index af6ac13..775fcce 100644
--- a/test/udls.cpp
+++ b/test/udls.cpp
@@ -10,3 +10,17 @@ TEST_CASE("compile-time named bools", "[utility]") {
     static_assert("variable"_true);
     static_assert(not "variable"_false);
 }
+
+TEST_CASE("decimal units", "[units]") {
+    using namespace stdx::literals;
+    static_assert(1_k == 1'000ull);
+    static_assert(1_M == 1'000'000ull);
+    static_assert(1_G == 1'000'000'000ull);
+}
+
+TEST_CASE("binary units", "[units]") {
+    using namespace stdx::literals;
+    static_assert(1_ki == 1'024ull);
+    static_assert(1_Mi == 1'024ull * 1'024ull);
+    static_assert(1_Gi == 1'024ull * 1'024ull * 1'024ull);
+}