implement WriteTag wipeout and shrinking options

src/Id3.Net/Id3/Id3Handler.cs

@@ -89,7 +89,7 @@ internal string GetFrameIdFromFrame(Id3Frame frame)
         internal abstract byte[] GetTagBytes(Stream stream);
         internal abstract bool HasTag(Stream stream);
         internal abstract Id3Tag ReadTag(Stream stream, out object additionalData);
-        internal abstract bool WriteTag(Stream stream, Id3Tag tag);
+        internal abstract bool WriteTag(Stream stream, Id3Tag tag, WriteTagOptions options);
         #endregion
 
         #region ID3 tag properties for the handler

src/Id3.Net/Id3/v1/Id3v1Handler.cs

@@ -98,7 +98,7 @@ internal override Id3Tag ReadTag(Stream stream, out object additionalData)
             return tag;
         }
 
-        internal override bool WriteTag(Stream stream, Id3Tag tag)
+        internal override bool WriteTag(Stream stream, Id3Tag tag, WriteTagOptions options)
         {
             Encoding encoding = TextEncodingHelper.GetDefaultEncoding();
 

src/Id3.Net/Id3/v2/Id3v23Handler.cs

@@ -1,4 +1,4 @@
-#region --- License & Copyright Notice ---
+    #region --- License & Copyright Notice ---
 /*
 Copyright (c) 2005-2019 Jeevan James
 All rights reserved.
@@ -156,7 +156,7 @@ internal override Id3Tag ReadTag(Stream stream, out object additionalData)
             return tag;
         }
 
-        internal override bool WriteTag(Stream stream, Id3Tag tag)
+        internal override bool WriteTag(Stream stream, Id3Tag tag, WriteTagOptions options)
         {
             byte[] tagBytes = GetTagBytes(tag);
             int requiredTagSize = tagBytes.Length;
@@ -165,7 +165,13 @@ internal override bool WriteTag(Stream stream, Id3Tag tag)
                 int currentTagSize = GetTagSize(stream);
                 if (requiredTagSize > currentTagSize)
                     MakeSpaceForTag(stream, currentTagSize, requiredTagSize);
-            } else
+                else if (requiredTagSize < currentTagSize)
+                    if (options.ShrinkFile && (currentTagSize - requiredTagSize) > options.ShrinkFileThreshold)
+                        ShrinkSpaceForTag(stream, currentTagSize, requiredTagSize);
+                    else if (options.WipeOut)
+                        WipeOutRemainingSpace(stream, currentTagSize, requiredTagSize);
+            }
+            else
                 MakeSpaceForTag(stream, 0, requiredTagSize);
 
             stream.Seek(0, SeekOrigin.Begin);
@@ -310,6 +316,39 @@ private static void MakeSpaceForTag(Stream stream, int currentTagSize, int requi
             }
         }
 
-        private const int BufferSize = 8192;
+        private static void ShrinkSpaceForTag(Stream stream, int currentTagSize, int requiredTagSize)
+        {
+            if (currentTagSize < requiredTagSize)
+                return;
+
+            int streamLength = (int)stream.Length;
+            var readPos = currentTagSize;
+            int writePos = requiredTagSize;
+
+            var buffer = new byte[BufferSize];
+            while (readPos < streamLength)
+            {
+                int bytesToRead = (readPos + BufferSize > streamLength) ? streamLength - readPos : BufferSize;
+                stream.Seek(readPos, SeekOrigin.Begin);
+                stream.Read(buffer, 0, bytesToRead);
+                stream.Seek(writePos, SeekOrigin.Begin);
+                stream.Write(buffer, 0, bytesToRead);
+                readPos += bytesToRead;
+                writePos += bytesToRead;
+            }
+            stream.SetLength(writePos);
+        }
+
+        private static void WipeOutRemainingSpace(Stream stream, int currentTagSize, int requiredTagSize)
+        {
+            if (currentTagSize < requiredTagSize)
+                return;
+
+            var remainingSize = currentTagSize - requiredTagSize;
+            stream.Seek(requiredTagSize, SeekOrigin.Begin);
+            stream.Write(new byte[remainingSize], 0, remainingSize);
+        }
+
+        private const int BufferSize = 512 * 1024;    // 8192 - memory is no big issue today, so reduce the seeking efforts
     }
 }

src/Id3.Net/Mp3/Mp3.cs

@@ -272,10 +272,26 @@ public bool HasTagOfVersion(Id3Version version) =>
         #region Tag writing methods
         public bool UpdateTag(Id3Tag tag)
         {
-            return WriteTag(tag, WriteConflictAction.Replace);
+            return WriteTag(tag, new WriteTagOptions() { ConflictAction = WriteConflictAction.Replace });
         }
 
         public bool WriteTag(Id3Tag tag, WriteConflictAction conflictAction = WriteConflictAction.NoAction)
+        {
+            return WriteTag(tag, new WriteTagOptions() { ConflictAction = conflictAction });
+        }
+
+        public bool WriteTag(Id3Tag tag, Id3Version version, WriteConflictAction conflictAction = WriteConflictAction.NoAction)
+        {
+            return WriteTag(tag, version, new WriteTagOptions() { ConflictAction = conflictAction });
+        }
+
+        public bool WriteTag(Id3Tag tag, Id3Version version, WriteTagOptions options)
+        {
+            tag.Version = version;
+            return WriteTag(tag, options);
+        }
+
+        public bool WriteTag(Id3Tag tag, WriteTagOptions options)
         {
             if (tag == null)
                 throw new ArgumentNullException(nameof(tag));
@@ -290,9 +306,9 @@ public bool WriteTag(Id3Tag tag, WriteConflictAction conflictAction = WriteConfl
                 Id3Handler handler = familyHandler;
                 if (handler.Version != tag.Version)
                 {
-                    if (conflictAction == WriteConflictAction.NoAction)
+                    if (options.ConflictAction == WriteConflictAction.NoAction)
                         return false;
-                    if (conflictAction == WriteConflictAction.Replace)
+                    if (options.ConflictAction == WriteConflictAction.Replace)
                     {
                         Id3Handler handlerCopy = handler; //TODO: Why did we need a copy of the handler?
                         handlerCopy.DeleteTag(Stream);
@@ -302,18 +318,11 @@ public bool WriteTag(Id3Tag tag, WriteConflictAction conflictAction = WriteConfl
 
             //Write the tag to the file. The handler will know how to overwrite itself.
             Id3Handler writeHandler = Id3Handler.GetHandler(tag.Version);
-            bool writeSuccessful = writeHandler.WriteTag(Stream, tag);
+            bool writeSuccessful = writeHandler.WriteTag(Stream, tag, options);
             if (writeSuccessful)
                 InvalidateExistingHandlers();
             return writeSuccessful;
         }
-
-        public bool WriteTag(Id3Tag tag, Id3Version version,
-            WriteConflictAction conflictAction = WriteConflictAction.NoAction)
-        {
-            tag.Version = version;
-            return WriteTag(tag, conflictAction);
-        }
         #endregion
 
         #region Audio stream members

src/Id3.Net/Mp3/WriteTagOptions.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Id3
+{
+    public class WriteTagOptions
+    {
+        public WriteConflictAction ConflictAction { get; set; } = WriteConflictAction.NoAction;
+
+        public bool WipeOut { get; set; } = true;
+
+        public bool ShrinkFile { get; set; } = true;
+
+        public int ShrinkFileThreshold { get; set; } = 0;
+    }
+}