//压缩字节

//1.创建压缩的数据流

//2.设定compressStream为存放被压缩的文件流,并设定为压缩模式

//3.将需要压缩的字节写到被压缩的文件流

public static byte[] CompressBytes(byte[] bytes)

{

    using(MemoryStream compressStream = new MemoryStream())

    {

        using(var zipStream = new GZipStream(compressStream, CompressMode.ComPress))

            zipStream.Write(bytes, , bytes.Length);

        return compressStream.ToArray();

    }

}

//解压缩字节

//1.创建被压缩的数据流

//2.创建zipStream对象，并传入解压的文件流

//3.创建目标流

//4.zipStream拷贝到目标流

//5.返回目标流输出字节

public static byte[] Decompress(byte[] bytes)

{

    using(var compressStream = new MemoryStream(bytes))

    {

        using(var zipStream = new GZipStream(compressStream, CompressMode.DeCompress))

        {

            using(var resultStream = new MemoryStream())

            {

                zipStream.CopyTo(resultStream);

                return resultStream.ToArray();

            }

        }

    }

}

class Program

    {

        public static int ReadAllBytesFromStream(Stream stream, byte[] buffer)

        {

            int offset = ;

            int totalCount = ;

            while (true)

            {

                int bytesRead = stream.Read(buffer, offset, );

                if (bytesRead == )

                {

                    break;

                }

                offset += bytesRead;

                totalCount += bytesRead;

            }

            return totalCount;

        }

        public static bool CompareData(byte[] buf1, int len1, byte[] buf2, int len2)

        {

            if (len1 != len2)

            {

                Console.WriteLine("Number of bytes in two buffer are diffreent {0}：{1}", len1, len2);

                return false;

            }

            for (int i = ; i < len1; i++)

            {

                if (buf1[i] != buf2[i])

                {

                    Console.WriteLine("byte {0} is different {1}{2}", i, buf1[i], buf2[i]);

                    return false;

                }

            }

            Console.WriteLine("All byte compare true");

            return true;

        }

        public static void GZipCompressDecompress(string fileName)

        {

            Console.WriteLine("Test compresssion and decompression on file {0}", fileName);

            FileStream infile;

            try

            {

                //Comopress

                infile = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);

                byte[] buffer = new byte[infile.Length];

                int count = infile.Read(buffer, , buffer.Length);

                if (count != buffer.Length)

                {

                    infile.Close();

                    infile.Dispose();

                    Console.WriteLine("Test Failed: Unable to read data from file");

                    return;

                }

                infile.Close();

                MemoryStream ms = new MemoryStream();

                GZipStream compressGZipStream = new GZipStream(ms, CompressionMode.Compress, true);

                Console.WriteLine("Compression");

                compressGZipStream.Write(buffer, , buffer.Length);    //从指定字节数组中将压缩的字节写入基础流

                compressGZipStream.Close();

                Console.WriteLine("Original size:{0}, Compressed size:{1}", buffer.Length, ms.ToArray().Length);

                //DeCompress

                ms.Position = ;

                GZipStream deCompressGZipStream = new GZipStream(ms, CompressionMode.Decompress);

                Console.WriteLine("Decompression");

                byte[] decompressedBuffer = new byte[buffer.Length + ];

                int totalCount = ReadAllBytesFromStream(deCompressGZipStream, decompressedBuffer);

                Console.WriteLine("Decompressed {0} bytes", totalCount);

                if (!CompareData(buffer, buffer.Length, decompressedBuffer, decompressedBuffer.Length))

                {

                    Console.WriteLine("Error. The two buffers did not compare.");

                }

                deCompressGZipStream.Dispose();

            }

            catch (ArgumentNullException)

            {

                Console.WriteLine("ArgumentNullException:{0}", "Error: The path is null.");

            }

            catch (ArgumentException)

            {

                Console.WriteLine("ArgumentException:{0}", "Error: path is a zero-length string, contains an empty string or one more invlaid characters");

            }

            catch (NotSupportedException)

            {

                Console.WriteLine("NotSupportedException:{0}", "Cite no file, such as 'con:'、'com1'、'lpt1' in NTFS");

            }

            catch (FileNotFoundException)

            {

                Console.WriteLine("FileNotFoundException:{0]", "Find no file");

            }

            catch (IOException)

            {

                Console.WriteLine("IOException:{0}", "Occur I/O error");

            }

            catch (System.Security.SecurityException)

            {

                Console.WriteLine("System.Security.SecurityException{0}:", "The calls has no permission");

            }

            catch (UnauthorizedAccessException)

            {

                Console.WriteLine("UnauthorizedAccessException：{0}", "path specified a file that is read-only, the path is a directory, " +

                    "or caller does not have the required permissions");

            }

        }

        static void Main(string[] args)

        {

            GZipCompressDecompress(@"D:\config.ini");

        }

    }