Ensure floating-point types write the exponent/significand as little-…

…endian (#68331)
dotnet · Apr 22, 2022 · 0e18cfd · Blackironman797 · Apr 22, 2022 · 0e18cfd
1 parent 9e9cfcb
commit 0e18cfd
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Showing 4 changed files with 42 additions and 2 deletions.
diff --git a/src/libraries/System.Private.CoreLib/src/System/Double.cs b/src/libraries/System.Private.CoreLib/src/System/Double.cs
@@ -11,6 +11,7 @@
 **
 ===========================================================*/
 
+using System.Buffers.Binary;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Numerics;
@@ -684,6 +685,12 @@ bool IFloatingPoint<double>.TryWriteExponentLittleEndian(Span<byte> destination,
             if (destination.Length >= sizeof(short))
             {
                 short exponent = Exponent;
+
+                if (!BitConverter.IsLittleEndian)
+                {
+                    exponent = BinaryPrimitives.ReverseEndianness(exponent);
+                }
+
                 Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), exponent);
 
                 bytesWritten = sizeof(short);
@@ -708,6 +715,12 @@ bool IFloatingPoint<double>.TryWriteSignificandLittleEndian(Span<byte> destinati
             if (destination.Length >= sizeof(ulong))
             {
                 ulong significand = Significand;
+
+                if (!BitConverter.IsLittleEndian)
+                {
+                    significand = BinaryPrimitives.ReverseEndianness(significand);
+                }
+
                 Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), significand);
 
                 bytesWritten = sizeof(ulong);

diff --git a/src/libraries/System.Private.CoreLib/src/System/Half.cs b/src/libraries/System.Private.CoreLib/src/System/Half.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Buffers.Binary;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
@@ -929,6 +930,12 @@ bool IFloatingPoint<Half>.TryWriteSignificandLittleEndian(Span<byte> destination
             if (destination.Length >= sizeof(ushort))
             {
                 ushort significand = Significand;
+
+                if (!BitConverter.IsLittleEndian)
+                {
+                    significand = BinaryPrimitives.ReverseEndianness(significand);
+                }
+
                 Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), significand);
 
                 bytesWritten = sizeof(ushort);

diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/NFloat.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/NFloat.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Buffers.Binary;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Numerics;
@@ -884,6 +885,12 @@ bool IFloatingPoint<NFloat>.TryWriteExponentLittleEndian(Span<byte> destination,
             if (destination.Length >= sizeof(NativeExponentType))
             {
                 NativeExponentType exponent = _value.Exponent;
+
+                if (!BitConverter.IsLittleEndian)
+                {
+                    exponent = BinaryPrimitives.ReverseEndianness(exponent);
+                }
+
                 Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), exponent);
 
                 bytesWritten = sizeof(NativeExponentType);
@@ -915,6 +922,12 @@ bool IFloatingPoint<NFloat>.TryWriteSignificandLittleEndian(Span<byte> destinati
             if (destination.Length >= sizeof(NativeSignificandType))
             {
                 NativeSignificandType significand = _value.Significand;
+
+                if (!BitConverter.IsLittleEndian)
+                {
+                    significand = BinaryPrimitives.ReverseEndianness(significand);
+                }
+
                 Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), significand);
 
                 bytesWritten = sizeof(NativeSignificandType);

diff --git a/src/libraries/System.Private.CoreLib/src/System/Single.cs b/src/libraries/System.Private.CoreLib/src/System/Single.cs
@@ -10,6 +10,7 @@
 **
 ===========================================================*/
 
+using System.Buffers.Binary;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Numerics;
@@ -174,9 +175,9 @@ public static unsafe bool IsNaN(float f)
             // A NaN will never equal itself so this is an
             // easy and efficient way to check for NaN.
 
-            #pragma warning disable CS1718
+#pragma warning disable CS1718
             return f != f;
-            #pragma warning restore CS1718
+#pragma warning restore CS1718
         }
 
         /// <summary>Determines whether the specified value is negative.</summary>
@@ -703,6 +704,12 @@ bool IFloatingPoint<float>.TryWriteSignificandLittleEndian(Span<byte> destinatio
             if (destination.Length >= sizeof(uint))
             {
                 uint significand = Significand;
+
+                if (!BitConverter.IsLittleEndian)
+                {
+                    significand = BinaryPrimitives.ReverseEndianness(significand);
+                }
+
                 Unsafe.WriteUnaligned(ref MemoryMarshal.GetReference(destination), significand);
 
                 bytesWritten = sizeof(uint);