Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Compilation/TimeStampChecker.cs

@@ -0,0 +1,99 @@
+//------------------------------------------------------------------------------
+// <copyright file="TimeStampChecker.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+namespace System.Web.Compilation {
+
+    using System;
+    using System.Collections;
+    using System.IO;
+    using System.Web;
+    using System.Web.Hosting;
+    using Debug = System.Web.Util.Debug;
+
+    internal class TimeStampChecker {
+        internal const String CallContextSlotName = "TSC";
+
+        private Hashtable _timeStamps = new Hashtable(StringComparer.OrdinalIgnoreCase);
+
+        private static TimeStampChecker Current {
+            get {
+                TimeStampChecker tsc = (TimeStampChecker)System.Runtime.Remoting.Messaging.CallContext.GetData(
+                    CallContextSlotName) as TimeStampChecker;
+
+                // Create it on demand
+                if (tsc == null) {
+                    tsc = new TimeStampChecker();
+                    Debug.Trace("TimeStampChecker", "Creating new TimeStampChecker");
+                    System.Runtime.Remoting.Messaging.CallContext.SetData(CallContextSlotName, tsc);
+                }
+
+                return tsc;
+            }
+        }
+
+        internal static void AddFile(string virtualPath, string path) {
+            Current.AddFileInternal(virtualPath, path);
+        }
+
+        private void AddFileInternal(string virtualPath, string path) {
+            DateTime lastWriteTimeUtc = File.GetLastWriteTimeUtc(path);
+
+            if (_timeStamps.Contains(virtualPath)) {
+                DateTime storedValue = (DateTime)_timeStamps[virtualPath];
+
+                // Already found to have changed before
+                if (storedValue == DateTime.MaxValue) {
+                    Debug.Trace("TimeStampChecker", "AddFileInternal: Same time stamp (" + path + ")");
+                    return;
+                }
+
+                // If it's different, set it to MaxValue as marker of being invalid
+                if (storedValue != lastWriteTimeUtc) {
+                    _timeStamps[virtualPath] = DateTime.MaxValue;
+                    Debug.Trace("TimeStampChecker", "AddFileInternal: Changed time stamp (" + path + ")");
+                }
+            }
+            else {
+                // New path: just add it
+                _timeStamps[virtualPath] = lastWriteTimeUtc;
+                Debug.Trace("TimeStampChecker", "AddFileInternal: New path (" + path + ")");
+            }
+        }
+
+        internal static bool CheckFilesStillValid(string key, ICollection virtualPaths) {
+            if (virtualPaths == null)
+                return true;
+
+            return Current.CheckFilesStillValidInternal(key, virtualPaths);
+        }
+
+        private bool CheckFilesStillValidInternal(string key, ICollection virtualPaths) {
+            Debug.Trace("TimeStampChecker", "CheckFilesStillValidInternal (" + key + ")");
+
+            foreach (string virtualPath in virtualPaths) {
+
+                if (!_timeStamps.Contains(virtualPath))
+                    continue;
+
+                string path = HostingEnvironment.MapPath(virtualPath);
+
+                DateTime lastWriteTimeUtc = File.GetLastWriteTimeUtc(path);
+                DateTime storedValue = (DateTime)_timeStamps[virtualPath];
+
+                // If it changed, then it's not valid
+                if (lastWriteTimeUtc != storedValue) {
+                    Debug.Trace("TimeStampChecker", "CheckFilesStillValidInternal: File (" + path + ") has changed!");
+
+                    return false;
+                }
+            }
+
+            Debug.Trace("TimeStampChecker", "CheckFilesStillValidInternal (" + key + ") is still valid");
+            return true;
+        }
+    }
+}
+