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diff --git a/src/dtf/WixToolset.Dtf.Compression/IUnpackStreamContext.cs b/src/dtf/WixToolset.Dtf.Compression/IUnpackStreamContext.cs
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+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Dtf.Compression
+{
+    using System;
+    using System.IO;
+
+    /// <summary>
+    /// This interface provides the methods necessary for the <see cref="CompressionEngine"/> to open
+    /// and close streams for archives and files. The implementor of this interface can use any
+    /// kind of logic to determine what kind of streams to open and where 
+    /// </summary>
+    public interface IUnpackStreamContext
+    {
+        /// <summary>
+        /// Opens the archive stream for reading.
+        /// </summary>
+        /// <param name="archiveNumber">The zero-based index of the archive to open.</param>
+        /// <param name="archiveName">The name of the archive being opened.</param>
+        /// <param name="compressionEngine">Instance of the compression engine doing the operations.</param>
+        /// <returns>A stream from which archive bytes are read, or null to cancel extraction
+        /// of the archive.</returns>
+        /// <remarks>
+        /// When the first archive in a chain is opened, the name is not yet known, so the
+        /// provided value will be an empty string. When opening further archives, the
+        /// provided value is the next-archive name stored in the previous archive. This
+        /// name is often, but not necessarily, the same as the filename of the archive
+        /// package to be opened.
+        /// <para>If this method returns null, the archive engine will throw a
+        /// FileNotFoundException.</para>
+        /// </remarks>
+        Stream OpenArchiveReadStream(int archiveNumber, string archiveName, CompressionEngine compressionEngine);
+
+        /// <summary>
+        /// Closes a stream where an archive package was read.
+        /// </summary>
+        /// <param name="archiveNumber">The archive number of the stream to close.</param>
+        /// <param name="archiveName">The name of the archive being closed.</param>
+        /// <param name="stream">The stream that was previously returned by
+        /// <see cref="OpenArchiveReadStream"/> and is now ready to be closed.</param>
+        void CloseArchiveReadStream(int archiveNumber, string archiveName, Stream stream);
+
+        /// <summary>
+        /// Opens a stream for writing extracted file bytes.
+        /// </summary>
+        /// <param name="path">The path of the file within the archive. This is often, but
+        /// not necessarily, the same as the relative path of the file outside the archive.</param>
+        /// <param name="fileSize">The uncompressed size of the file to be extracted.</param>
+        /// <param name="lastWriteTime">The last write time of the file to be extracted.</param>
+        /// <returns>A stream where extracted file bytes are to be written, or null to skip
+        /// extraction of the file and continue to the next file.</returns>
+        /// <remarks>
+        /// The implementor may use the path, size and date information to dynamically
+        /// decide whether or not the file should be extracted.
+        /// </remarks>
+        Stream OpenFileWriteStream(string path, long fileSize, DateTime lastWriteTime);
+
+        /// <summary>
+        /// Closes a stream where an extracted file was written.
+        /// </summary>
+        /// <param name="path">The path of the file within the archive.</param>
+        /// <param name="stream">The stream that was previously returned by <see cref="OpenFileWriteStream"/>
+        /// and is now ready to be closed.</param>
+        /// <param name="attributes">The attributes of the extracted file.</param>
+        /// <param name="lastWriteTime">The last write time of the file.</param>
+        /// <remarks>
+        /// The implementor may wish to apply the attributes and date to the newly-extracted file.
+        /// </remarks>
+        void CloseFileWriteStream(string path, Stream stream, FileAttributes attributes, DateTime lastWriteTime);
+    }
+}