Add project files.

AssetStudio/SevenZipHelper.cs

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+using System;
+using System.IO;
+using SevenZip.Compression.LZMA;
+
+
+namespace AssetStudio
+{
+    public static class SevenZipHelper
+    {
+        public static MemoryStream StreamDecompress(MemoryStream inStream)
+        {
+            var decoder = new Decoder();
+
+            inStream.Seek(0, SeekOrigin.Begin);
+            var newOutStream = new MemoryStream();
+
+            var properties = new byte[5];
+            if (inStream.Read(properties, 0, 5) != 5)
+                throw new Exception("input .lzma is too short");
+            long outSize = 0;
+            for (var i = 0; i < 8; i++)
+            {
+                var v = inStream.ReadByte();
+                if (v < 0)
+                    throw new Exception("Can't Read 1");
+                outSize |= ((long)(byte)v) << (8 * i);
+            }
+            decoder.SetDecoderProperties(properties);
+
+            var compressedSize = inStream.Length - inStream.Position;
+            decoder.Code(inStream, newOutStream, compressedSize, outSize, null);
+
+            newOutStream.Position = 0;
+            return newOutStream;
+        }
+
+        public static void StreamDecompress(Stream compressedStream, Stream decompressedStream, long compressedSize, long decompressedSize)
+        {
+            var basePosition = compressedStream.Position;
+            var decoder = new Decoder();
+            var properties = new byte[5];
+            if (compressedStream.Read(properties, 0, 5) != 5)
+                throw new Exception("input .lzma is too short");
+            decoder.SetDecoderProperties(properties);
+            decoder.Code(compressedStream, decompressedStream, compressedSize - 5, decompressedSize, null);
+            compressedStream.Position = basePosition + compressedSize;
+        }
+    }
+}