maintenance expiration vs build date checking code

server/AyaNova/util/FileUtil.cs

@@ -8,6 +8,7 @@ using Microsoft.Extensions.Logging;
 using Microsoft.EntityFrameworkCore;
 using AyaNova.Models;
 using AyaNova.Biz;
+using System.Reflection;
 
 namespace AyaNova.Util
 {
@@ -481,7 +482,7 @@ namespace AyaNova.Util
                 AttachToAType = attachToObject.AType,
                 LastModified = lastModified,
                 Size = FileSize,
-                AttachedByUserId=attachedByUserId
+                AttachedByUserId = attachedByUserId
 
             };
 
@@ -828,7 +829,7 @@ namespace AyaNova.Util
             {
                 return string.Empty;
             }
-           
+
             //Linux ~ home folder special handling here
             if (path.Contains('~'))
             {
@@ -841,6 +842,34 @@ namespace AyaNova.Util
         }
         #endregion general utilities
 
+
+        #region licensing related utility to qualify upgradability
+        //https://www.meziantou.net/getting-the-date-of-build-of-a-dotnet-assembly-at-runtime.htm
+        public static DateTime GetLinkerTimestampUtc(Assembly assembly)
+        {
+            var location = assembly.Location;
+            return GetLinkerTimestampUtc(location);
+        }
+
+        public static DateTime GetLinkerTimestampUtc(string filePath)
+        {
+            const int peHeaderOffset = 60;
+            const int linkerTimestampOffset = 8;
+            var bytes = new byte[2048];
+
+            using (var file = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
+            {
+                file.Read(bytes, 0, bytes.Length);
+            }
+
+            var headerPos = BitConverter.ToInt32(bytes, peHeaderOffset);
+            var secondsSince1970 = BitConverter.ToInt32(bytes, headerPos + linkerTimestampOffset);
+            var dt = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+            return dt.AddSeconds(secondsSince1970);
+        }
+        #endregion
+
+
     }//eoc
 
 }//eons