Rename mscorlib to System.Private.Corelib (#17926)

* diff from just renaming folder mscorlib to System.Private.CoreLib

* Updating build.proj to reflect name change

Fixes: #17905

1 files changed, 38 insertions, 0 deletions

diff --git a/src/System.Private.CoreLib/shared/System/Guid.Unix.cs b/src/System.Private.CoreLib/shared/System/Guid.Unix.cs
new file mode 100644
index 0000000000..442e7f8837
--- /dev/null
+++ b/src/System.Private.CoreLib/shared/System/Guid.Unix.cs
@@ -0,0 +1,38 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+namespace System
+{
+    partial struct Guid
+    {
+        // This will create a new random guid based on the https://www.ietf.org/rfc/rfc4122.txt 
+        public static unsafe Guid NewGuid()
+        {
+            Guid g;
+            Interop.GetRandomBytes((byte*)&g, sizeof(Guid));
+            
+            const ushort VersionMask = 0xF000;
+            const ushort RandomGuidVersion = 0x4000;
+
+            const byte ClockSeqHiAndReservedMask = 0xC0;
+            const byte ClockSeqHiAndReservedValue = 0x80;
+
+            // Modify bits indicating the type of the GUID
+
+            unchecked
+            {
+                // time_hi_and_version
+                g._c = (short)((g._c & ~VersionMask) | RandomGuidVersion);
+                // clock_seq_hi_and_reserved
+                g._d = (byte)((g._d & ~ClockSeqHiAndReservedMask) | ClockSeqHiAndReservedValue);
+            }
+
+            return g;
+        }
+    }
+}
+