From 0c7cf6f6d3a85c6a5cda60d8840b3a0660eeb64d Mon Sep 17 00:00:00 2001
From: Rafal Kupiec <belliash@codingworkshop.eu.org>
Date: Wed, 21 Feb 2024 19:55:16 +0100
Subject: [PATCH] Implement RtlInfiniteDouble() and RtlNanDouble() routines

---
 xtoskrnl/includes/rtli.h |  8 +++++
 xtoskrnl/rtl/math.c      | 68 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/xtoskrnl/includes/rtli.h b/xtoskrnl/includes/rtli.h
index d6f12a7f..bd5fd51a 100644
--- a/xtoskrnl/includes/rtli.h
+++ b/xtoskrnl/includes/rtli.h
@@ -260,6 +260,10 @@ LONG
 RtlGetBaseExponent(IN DOUBLE Value,
                    OUT PDOUBLE PowerOfTen);
 
+XTCDECL
+BOOLEAN
+RtlInfiniteDouble(IN DOUBLE Value);
+
 XTCDECL
 VOID
 RtlInitializeListHead(IN PLIST_ENTRY ListHead);
@@ -286,6 +290,10 @@ XTCDECL
 BOOLEAN
 RtlListLoop(IN PLIST_ENTRY ListHead);
 
+XTCDECL
+BOOLEAN
+RtlNanDouble(IN DOUBLE Value);
+
 XTCDECL
 VOID
 RtlRemoveEntryList(IN PLIST_ENTRY Entry);
diff --git a/xtoskrnl/rtl/math.c b/xtoskrnl/rtl/math.c
index 37944d05..6261e93b 100644
--- a/xtoskrnl/rtl/math.c
+++ b/xtoskrnl/rtl/math.c
@@ -600,6 +600,40 @@ RtlGetBaseExponent(IN DOUBLE Value,
     return Exponent;
 }
 
+/**
+ * Determines whether a floating-point number is infinite.
+ *
+ * @param Value
+ *        Supplies the floating-point value to test.
+ *
+ * @return This routine returns TRUE if the argument is infinite or a NaN, or FALSE otherwise.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+BOOLEAN
+RtlInfiniteDouble(IN DOUBLE Value)
+{
+    /* DOUBLE argument in IEEE 754 standard format */
+    union
+    {
+        PDOUBLE Double;
+        struct
+        {
+            UINT MantissaLow:32;
+            UINT MantissaHigh:20;
+            UINT Exponent:11;
+            UINT Sign:1;
+        } *DoubleS;
+    } Var;
+
+    /* Convert input double value to IEEE 754 format */
+    Var.Double = &Value;
+
+    /* Return TRUE if it is infinite, or FALSE otherwise */
+    return ((Var.DoubleS->Exponent & 0x7FF) == 0x7FF);
+}
+
 /**
  * Multiplies a signed large integer by a signed integer.
  *
@@ -624,3 +658,37 @@ RtlMultiplyLargeInteger(IN LARGE_INTEGER Multiplicand,
     LargeInt.QuadPart = (LONGLONG) Multiplicand.QuadPart * Multiplier;
     return LargeInt;
 }
+
+/**
+ * Determines whether a floating-point number is a NaN ("Not a Number").
+ *
+ * @param Value
+ *        Supplies the floating-point value to test.
+ *
+ * @return This routine returns TRUE if the argument is a NaN, or FALSE otherwise.
+ *
+ * @since XT 1.0
+ */
+XTCDECL
+BOOLEAN
+RtlNanDouble(IN DOUBLE Value)
+{
+    /* DOUBLE argument in IEEE 754 standard format */
+    union
+    {
+        PDOUBLE Double;
+        struct
+        {
+            UINT MantissaLow:32;
+            UINT MantissaHigh:20;
+            UINT Exponent:11;
+            UINT Sign:1;
+        } *DoubleS;
+    } Var;
+
+    /* Convert input double value to IEEE 754 format */
+    Var.Double = &Value;
+
+    /* Return TRUE if it is NaN, or FALSE otherwise */
+    return (Var.DoubleS->Exponent == 0x7FF && (Var.DoubleS->MantissaHigh != 0 || Var.DoubleS->MantissaLow != 0));
+}