Create and using PauseEntryRebuilding for adding large numbers of ent…

src/SharpCompress/Archives/AbstractWritableArchive.cs

@@ -12,11 +12,28 @@ public abstract class AbstractWritableArchive<TEntry, TVolume> : AbstractArchive
         where TEntry : IArchiveEntry
         where TVolume : IVolume
     {
+        private class RebuildPauseDisposable: IDisposable
+        {
+            private readonly AbstractWritableArchive<TEntry, TVolume> archive;
+
+            public RebuildPauseDisposable(AbstractWritableArchive<TEntry, TVolume> archive)
+            {
+                this.archive = archive;
+                archive.pauseRebuilding = true;
+            }
+
+            public void Dispose()
+            {
+                archive.pauseRebuilding = false;
+                archive.RebuildModifiedCollection();
+            }
+        }
         private readonly List<TEntry> newEntries = new List<TEntry>();
         private readonly List<TEntry> removedEntries = new List<TEntry>();
 
         private readonly List<TEntry> modifiedEntries = new List<TEntry>();
         private bool hasModifications;
+        private bool pauseRebuilding;
 
         internal AbstractWritableArchive(ArchiveType type)
             : base(type)
@@ -47,8 +64,17 @@ public override ICollection<TEntry> Entries
             }
         }
 
+        public IDisposable PauseEntryRebuilding()
+        {
+            return new RebuildPauseDisposable(this);
+        }
+
         private void RebuildModifiedCollection()
         {
+            if (pauseRebuilding)
+            {
+                return;
+            }
             hasModifications = true;
             newEntries.RemoveAll(v => removedEntries.Contains(v));
             modifiedEntries.Clear();

src/SharpCompress/Archives/IWritableArchive.cs

@@ -11,5 +11,11 @@ public interface IWritableArchive : IArchive
         IArchiveEntry AddEntry(string key, Stream source, bool closeStream, long size = 0, DateTime? modified = null);
 
         void SaveTo(Stream stream, WriterOptions options);
+
+        /// <summary>
+        /// Use this to pause entry rebuilding when adding large collections of entries.  Dispose when complete.  A  using statement is recommended.
+        /// </summary>
+        /// <returns>IDisposeable to resume entry rebuilding</returns>
+        IDisposable PauseEntryRebuilding();
     }
 }

src/SharpCompress/Archives/IWritableArchiveExtensions.cs

@@ -39,15 +39,21 @@ public static void SaveTo(this IWritableArchive writableArchive, FileInfo fileIn
             this IWritableArchive writableArchive,
             string filePath, string searchPattern = "*.*", SearchOption searchOption = SearchOption.AllDirectories)
         {
+            using (writableArchive.PauseEntryRebuilding())
+            {
 #if NET35
-            foreach (var path in Directory.GetFiles(filePath, searchPattern, searchOption))
+                foreach (var path in Directory.GetFiles(filePath, searchPattern, searchOption))
 #else
-            foreach (var path in Directory.EnumerateFiles(filePath, searchPattern, searchOption))
+                foreach (var path in Directory.EnumerateFiles(filePath, searchPattern, searchOption))
 #endif
-            {
-                var fileInfo = new FileInfo(path);
-                writableArchive.AddEntry(path.Substring(filePath.Length), fileInfo.OpenRead(), true, fileInfo.Length,
-                                         fileInfo.LastWriteTime);
+                {
+                    var fileInfo = new FileInfo(path);
+                    writableArchive.AddEntry(path.Substring(filePath.Length),
+                                             fileInfo.OpenRead(),
+                                             true,
+                                             fileInfo.Length,
+                                             fileInfo.LastWriteTime);
+                }
             }
         }
         public static IArchiveEntry AddEntry(this IWritableArchive writableArchive, string key, FileInfo fileInfo)