add FinishSizePrefixed methods to CSharp FlatBufferBuilder as well

net/FlatBuffers/FlatBufferBuilder.cs

@@ -580,6 +580,25 @@ namespace FlatBuffers
         }
         /// @endcond
 
+        /// <summary>
+        /// Finalize a buffer, pointing to the given `root_table`.
+        /// </summary>
+        /// <param name="rootTable">
+        /// An offset to be added to the buffer.
+        /// </param>
+        /// <param name="sizePrefix">
+        /// Whether to prefix the size to the buffer.
+        /// </param>
+        protected void Finish(int rootTable, bool sizePrefix)
+        {
+            Prep(_minAlign, sizeof(int) + (sizePrefix ? sizeof(int) : 0));
+            AddOffset(rootTable);
+            if (sizePrefix) {
+                AddInt(_bb.Length - _space);
+            }
+            _bb.Position = _space;
+        }
+
         /// <summary>
         /// Finalize a buffer, pointing to the given `root_table`.
         /// </summary>
@@ -588,9 +607,18 @@ namespace FlatBuffers
         /// </param>
         public void Finish(int rootTable)
         {
-            Prep(_minAlign, sizeof(int));
+            Finish(rootTable, false);
-            AddOffset(rootTable);
+        }
-            _bb.Position = _space;
+
+        /// <summary>
+        /// Finalize a buffer, pointing to the given `root_table`, with the size prefixed.
+        /// </summary>
+        /// <param name="rootTable">
+        /// An offset to be added to the buffer.
+        /// </param>
+        public void FinishSizePrefixed(int rootTable)
+        {
+            Finish(rootTable, true);
         }
 
         /// <summary>
@@ -631,9 +659,12 @@ namespace FlatBuffers
         /// A FlatBuffer file identifier to be added to the buffer before
         /// `root_table`.
         /// </param>
-         public void Finish(int rootTable, string fileIdentifier)
+        /// <param name="sizePrefix">
+        /// Whether to prefix the size to the buffer.
+        /// </param>
+        protected void Finish(int rootTable, string fileIdentifier, bool sizePrefix)
         {
-             Prep(_minAlign, sizeof(int) +
+            Prep(_minAlign, sizeof(int) + (sizePrefix ? sizeof(int) : 0) +
                             FlatBufferConstants.FileIdentifierLength);
             if (fileIdentifier.Length !=
                 FlatBufferConstants.FileIdentifierLength)
@@ -646,10 +677,38 @@ namespace FlatBuffers
             {
                AddByte((byte)fileIdentifier[i]);
             }
-             Finish(rootTable);
+            Finish(rootTable, sizePrefix);
         }
 
+        /// <summary>
+        /// Finalize a buffer, pointing to the given `rootTable`.
+        /// </summary>
+        /// <param name="rootTable">
+        /// An offset to be added to the buffer.
+        /// </param>
+        /// <param name="fileIdentifier">
+        /// A FlatBuffer file identifier to be added to the buffer before
+        /// `root_table`.
+        /// </param>
+        public void Finish(int rootTable, string fileIdentifier)
+        {
+            Finish(rootTable, fileIdentifier, false);
+        }
 
+        /// <summary>
+        /// Finalize a buffer, pointing to the given `rootTable`, with the size prefixed.
+        /// </summary>
+        /// <param name="rootTable">
+        /// An offset to be added to the buffer.
+        /// </param>
+        /// <param name="fileIdentifier">
+        /// A FlatBuffer file identifier to be added to the buffer before
+        /// `root_table`.
+        /// </param>
+        public void FinishSizePrefixed(int rootTable, string fileIdentifier)
+        {
+            Finish(rootTable, fileIdentifier, true);
+        }
     }
 }