Add std::format / std::formatter for win32 HKEY

src/Windows/libraries/formatters/include/CMakeLists.txt

@@ -5,6 +5,7 @@ target_sources(m_formatters PUBLIC FILE_SET HEADERS FILES
     m/formatters/FILE_ACTION.h
     m/formatters/FILE_NOTIFY_EXTENDED_INFORMATION.h
     m/formatters/FILE_NOTIFY_INFORMATION.h
+    m/formatters/HKEY.h
     m/formatters/HRESULT.h
     m/formatters/NTSTATUS.h
     m/formatters/OVERLAPPED.h

src/Windows/libraries/formatters/include/m/formatters/HKEY.h

@@ -0,0 +1,82 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+#pragma once
+
+#include <algorithm>
+#include <array>
+#include <chrono>
+#include <format>
+#include <string_view>
+
+#include <Windows.h>
+
+using namespace std::string_view_literals;
+
+template <typename CharT>
+struct std::formatter<HKEY, CharT>
+{
+    template <typename ParseContext>
+    constexpr ParseContext::iterator
+    parse(ParseContext& ctx)
+    {
+        auto       it  = ctx.begin();
+        auto const end = ctx.end();
+
+        if (it != end && *it != '}')
+            throw std::format_error("Invalid format string");
+
+        return it;
+    }
+
+    template <typename FormatContext>
+    FormatContext::iterator
+    format(HKEY hkey, FormatContext& ctx) const
+    {
+        auto out = ctx.out();
+
+        //
+        // Macros are to be hated but they are to be tolerated here.
+        //
+        // There are a number of "named" HKEY values.
+        //
+
+#pragma push_macro("X")
+
+#undef X
+#define X(p)                                                                                       \
+    case reinterpret_cast<uint64_t>(p):                                                                 \
+    {                                                                                              \
+        constexpr auto lit = #p##sv;                                                               \
+        return std::ranges::copy(lit.begin(), lit.end(), out).out;                                 \
+    }
+
+        switch (reinterpret_cast<uint64_t>(hkey))
+        {
+            X(HKEY_CURRENT_USER)
+            X(HKEY_CLASSES_ROOT)
+            X(HKEY_LOCAL_MACHINE)
+            X(HKEY_USERS)
+            X(HKEY_PERFORMANCE_DATA)
+            X(HKEY_PERFORMANCE_TEXT)
+            X(HKEY_PERFORMANCE_NLSTEXT)
+            X(HKEY_CURRENT_CONFIG)
+            X(HKEY_DYN_DATA)
+            X(HKEY_CURRENT_USER_LOCAL_SETTINGS)
+        }
+
+#pragma pop_macro("X")
+
+        if constexpr (std::is_same_v<CharT, char>)
+        {
+            return std::format_to(out, "{{hkey 0x{:x}}}", reinterpret_cast<uintptr_t>(hkey));
+        }
+        else if constexpr (std::is_same_v<CharT, wchar_t>)
+        {
+            return std::format_to(out, L"{{hkey 0x{:x}}}", reinterpret_cast<uintptr_t>(hkey));
+        }
+        else
+        {
+            throw std::runtime_error("Bad CharT");
+        }
+    }
+};

src/Windows/libraries/formatters/test/CMakeLists.txt

@@ -9,11 +9,12 @@ add_executable(${TEST_EXE_NAME}
     test_FILE_ACTION.cpp
     test_FILE_NOTIFY_EXTENDED_INFORMATION.cpp
     test_FILE_NOTIFY_INFORMATION.cpp
+    test_HKEY.cpp
     test_HRESULT.cpp
     test_NTSTATUS.cpp
     test_OVERLAPPED.cpp
     test_Win32ErrorCode.cpp
-)
+ )
 
 target_compile_features(${TEST_EXE_NAME} PUBLIC ${M_CXX_STD})
 

src/Windows/libraries/formatters/test/test_HKEY.cpp

@@ -0,0 +1,34 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+#include <gtest/gtest.h>
+
+#include <format>
+#include <string>
+#include <string_view>
+
+#include <m/formatters/HKEY.h>
+
+#include <Windows.h>
+
+using namespace std::string_literals;
+using namespace std::string_view_literals;
+
+TEST(HKEY, format_HKEY_CURRENT_USER)
+{
+    auto s = std::format(L"{}", HKEY_CURRENT_USER);
+    EXPECT_EQ(s, L"HKEY_CURRENT_USER"s);
+}
+
+TEST(HKEY, format_HKEY_LOCAL_MACHINE)
+{
+    auto s = std::format(L"{}", HKEY_LOCAL_MACHINE);
+    EXPECT_EQ(s, L"HKEY_LOCAL_MACHINE"s);
+}
+
+TEST(HKEY, format_default_hkey)
+{
+    auto s = std::format(L"{}", HKEY{});
+    EXPECT_EQ(s, L"{hkey 0x0}"s);
+}
+