GZipStream 压缩问题(丢失字节)

问题描述

我在使用 GZip Serializer 时遇到了一些奇怪的问题.

I've got some strange problem with GZip Serializer.

尝试序列化包含数据的对象.

Trying serializing object with data in it.

以下代码给出结果(在调试中的 POINT1):ms.Length = 100028 和 uncompressedStream.Length=100027

Following code give results(at POINT1 in debug): ms.Length = 100028 and uncompressedStream.Length=100027

在 POINT1 之后出现异常在解析完成之前遇到流结束."，我认为这是丢失字节的结果.

After POINT1 there is exception "End of Stream encountered before parsing was completed.", which i think is result of this lost byte.

我使用的是 .net 4.0.

I am using .net 4.0.

        //generating data
        int length = 100000;
        byte[] data = new byte[length];
        for (int i = 0; i < length; i++)
        {
            data[i] = System.Convert.ToByte(i % 100 + i % 50);
        }


        //serialization into memory stream
        IFormatter formatter = new BinaryFormatter();
        var ms = new MemoryStream();
        formatter.Serialize(ms, data);
        ms.Seek(0, SeekOrigin.Begin);

        //GZip zip
        MemoryStream compressedStream = new MemoryStream();
        var Compress = new GZipStream(compressedStream, CompressionMode.Compress);
        ms.CopyTo(Compress);  
        compressedStream.Seek(0, SeekOrigin.Begin);

        //GZip Unzip
        MemoryStream uncompressedStream = new MemoryStream();
        var Decompress = new GZipStream(compressedStream, CompressionMode.Decompress);
        Decompress.CopyTo(uncompressedStream);
        uncompressedStream.Seek(0, SeekOrigin.Begin);

        //deserialization from memory stream
        //POINT1
        var oo = formatter.Deserialize(uncompressedStream);
        var o = (byte[])oo;

        //checking
        Assert.AreEqual(data.Length, o.Length);
        for (int i = 0; i < data.Length; i++)
            Assert.AreEqual(data[i], o[i]);

推荐答案

压缩流在关闭之前不会刷新(并且无法正确刷新).您需要关闭 GZipStream.告诉它不要关闭底层流(构造函数参数之一)将使这更容易.

Compression streams don't flush (and can't properly flush) until they are closed. You will need to close the GZipStream. Telling it not to close the underlying stream (one of the constructor arguments) will make this easier.

        //generating data
        int length = 100000;
        byte[] data = new byte[length];
        for (int i = 0; i < length; i++)
        {
            data[i] = System.Convert.ToByte(i % 100 + i % 50);
        }

        byte[] o;
        //serialization into memory stream
        IFormatter formatter = new BinaryFormatter();
        using (var ms = new MemoryStream())
        {
            formatter.Serialize(ms, data);
            ms.Seek(0, SeekOrigin.Begin);

            //GZip zip
            using(MemoryStream compressedStream = new MemoryStream())
            {
                using (var Compress = new GZipStream(compressedStream, CompressionMode.Compress, true))
                {
                    ms.CopyTo(Compress);
                }
                compressedStream.Seek(0, SeekOrigin.Begin);
                //GZip Unzip
                using (MemoryStream uncompressedStream = new MemoryStream())
                {
                    using (var Decompress = new GZipStream(compressedStream, CompressionMode.Decompress, true))
                    {
                        Decompress.CopyTo(uncompressedStream);
                    }
                    uncompressedStream.Seek(0, SeekOrigin.Begin);
                    var oo = formatter.Deserialize(uncompressedStream);
                    o = (byte[])oo;
                }
            }
            //deserialization from memory stream
            //POINT1

        }
        //checking
        Debug.Assert(data.Length == o.Length);
        for (int i = 0; i < data.Length; i++)
            Debug.Assert(data[i] == o[i]);