From 59c55e003e706ec9ccd7df80dcdc2b96eb0e3226 Mon Sep 17 00:00:00 2001
From: Timo Kreuzer <timo.kreuzer@reactos.org>
Date: Fri, 15 Nov 2024 16:53:39 +0200
Subject: [PATCH] [UCRT:MATH] Implement _dclass, _fdclass

---
 sdk/lib/ucrt/math/_dclass.c  | 48 ++++++++++++++++++++++++++++++++++++
 sdk/lib/ucrt/math/_fdclass.c | 48 ++++++++++++++++++++++++++++++++++++
 sdk/lib/ucrt/math/math.cmake |  2 ++
 3 files changed, 98 insertions(+)
 create mode 100644 sdk/lib/ucrt/math/_dclass.c
 create mode 100644 sdk/lib/ucrt/math/_fdclass.c

diff --git a/sdk/lib/ucrt/math/_dclass.c b/sdk/lib/ucrt/math/_dclass.c
new file mode 100644
index 00000000000..aeeff8ccde0
--- /dev/null
+++ b/sdk/lib/ucrt/math/_dclass.c
@@ -0,0 +1,48 @@
+//
+// _dclass.c
+//
+//      Copyright (c) 2024 Timo Kreuzer
+//
+// Implementation of _dclass.
+//
+// SPDX-License-Identifier: MIT
+//
+
+#include <math.h>
+#include <stdint.h>
+
+#ifdef _MSC_VER
+#pragma function(_dclass)
+#endif
+
+//
+// Returns the floating-point classification of _X.
+//
+//     FP_NAN - A quiet, signaling, or indeterminate NaN
+//     FP_INFINITE - A positive or negative infinity
+//     FP_NORMAL - A positive or negative normalized non-zero value
+//     FP_SUBNORMAL - A positive or negative subnormal (denormalized) value
+//     FP_ZERO - A positive or negative zero value
+//
+_Check_return_
+short
+__cdecl
+_dclass(_In_ double _X)
+{
+    union { double f; uint64_t ui64; } u = { _X };
+    uint64_t e = u.ui64 & 0x7FF0000000000000ull;
+    uint64_t m = u.ui64 & 0x000FFFFFFFFFFFFFull;
+
+    if (e == 0x7FF0000000000000ull)
+    {
+        return m ? FP_NAN : FP_INFINITE;
+    }
+    else if (e == 0)
+    {
+        return m ? FP_SUBNORMAL : FP_ZERO;
+    }
+    else
+    {
+        return FP_NORMAL;
+    }
+}
diff --git a/sdk/lib/ucrt/math/_fdclass.c b/sdk/lib/ucrt/math/_fdclass.c
new file mode 100644
index 00000000000..4714a9d6664
--- /dev/null
+++ b/sdk/lib/ucrt/math/_fdclass.c
@@ -0,0 +1,48 @@
+//
+// _fdclass.c
+//
+//      Copyright (c) 2024 Timo Kreuzer
+//
+// Implementation of _fdclass.
+//
+// SPDX-License-Identifier: MIT
+//
+
+#include <math.h>
+#include <stdint.h>
+
+#ifdef _MSC_VER
+#pragma function(_fdclass)
+#endif
+
+//
+// Returns the floating-point classification of _X.
+//
+//     FP_NAN - A quiet, signaling, or indeterminate NaN
+//     FP_INFINITE - A positive or negative infinity
+//     FP_NORMAL - A positive or negative normalized non-zero value
+//     FP_SUBNORMAL - A positive or negative subnormal (denormalized) value
+//     FP_ZERO - A positive or negative zero value
+//
+_Check_return_
+short
+__cdecl
+_fdclass(_In_ float _X)
+{
+    union { float f; uint32_t ui32; } u = { _X };
+    uint32_t e = u.ui32 & 0x7F800000u;
+    uint32_t m = u.ui32 & 0x007FFFFFu;
+
+    if (e == 0x7F800000u)
+    {
+        return m ? FP_NAN : FP_INFINITE;
+    }
+    else if (e == 0)
+    {
+        return m ? FP_SUBNORMAL : FP_ZERO;
+    }
+    else
+    {
+        return FP_NORMAL;
+    }
+}
diff --git a/sdk/lib/ucrt/math/math.cmake b/sdk/lib/ucrt/math/math.cmake
index 4eadd9f107d..69f213e743f 100644
--- a/sdk/lib/ucrt/math/math.cmake
+++ b/sdk/lib/ucrt/math/math.cmake
@@ -1,4 +1,6 @@
 
 list(APPEND UCRT_MATH_SOURCES
+    math/_dclass.c
+    math/_fdclass.c
     math/matherr.cpp
 )