GZip解压缩

public class GZipHelper
    {
        public static void DecompressFile(string sourceFile, string destinationFile)
        {
            // make sure the source file is there
            if (File.Exists(sourceFile) == false)
                throw new FileNotFoundException();

            // Create the streams and byte arrays needed
            FileStream sourceStream = null;
            FileStream destinationStream = null;
            GZipStream decompressedStream = null;
            byte[] quartetBuffer = null;

            try
            {
                // Read in the compressed source stream
                sourceStream = new FileStream(sourceFile, FileMode.Open);

                // Create a compression stream pointing to the destiantion stream
                decompressedStream = new GZipStream(sourceStream, CompressionMode.Decompress, true);

                // Read the footer to determine the length of the destiantion file
                quartetBuffer = new byte[4];
                int position = (int)sourceStream.Length - 4;
                sourceStream.Position = position;
                sourceStream.Read(quartetBuffer, 0, 4);
                sourceStream.Position = 0;
                int checkLength = BitConverter.ToInt32(quartetBuffer, 0);

                byte[] buffer = new byte[checkLength + 100];

                int offset = 0;
                int total = 0;

                // Read the compressed data into the buffer
                while (true)
                {
                    int bytesRead = decompressedStream.Read(buffer, offset, 100);

                    if (bytesRead == 0)
                        break;

                    offset += bytesRead;
                    total += bytesRead;
                }

                // Now write everything to the destination file
                destinationStream = new FileStream(destinationFile, FileMode.Create);
                destinationStream.Write(buffer, 0, total);

                // and flush everyhting to clean out the buffer
                destinationStream.Flush();
            }
            catch (ApplicationException ex)
            {
                //MessageBox.Show(ex.Message, "解压文件时发生错误：", MessageBoxButtons.OK, MessageBoxIcon.Error);
                throw ex;
            }
            finally
            {
                // Make sure we allways close all streams
                if (sourceStream != null)
                    sourceStream.Close();

                if (decompressedStream != null)
                    decompressedStream.Close();

                if (destinationStream != null)
                    destinationStream.Close();
            }

        }

        public static void CompressFile(string sourceFile, string destinationFile)
        {
            // make sure the source file is there
            if (File.Exists(sourceFile) == false)
                throw new FileNotFoundException();

            // Create the streams and byte arrays needed
            byte[] buffer = null;
            FileStream sourceStream = null;
            FileStream destinationStream = null;
            GZipStream compressedStream = null;

            try
            {
                // Read the bytes from the source file into a byte array
                sourceStream = new FileStream(sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read);

                // Read the source stream values into the buffer
                buffer = new byte[sourceStream.Length];
                int checkCounter = sourceStream.Read(buffer, 0, buffer.Length);

                if (checkCounter != buffer.Length)
                {
                    throw new ApplicationException();
                }

                // Open the FileStream to write to
                destinationStream = new FileStream(destinationFile, FileMode.OpenOrCreate, FileAccess.Write);

                // Create a compression stream pointing to the destiantion stream
                compressedStream = new GZipStream(destinationStream, CompressionMode.Compress, true);

                // Now write the compressed data to the destination file
                compressedStream.Write(buffer, 0, buffer.Length);
            }
            catch (ApplicationException ex)
            {
                //MessageBox.Show(ex.Message, "压缩文件时发生错误：", MessageBoxButtons.OK, MessageBoxIcon.Error);
                throw ex;
            }
            finally
            {
                // Make sure we allways close all streams
                if (sourceStream != null)
                    sourceStream.Close();

                if (compressedStream != null)
                    compressedStream.Close();

                if (destinationStream != null)
                    destinationStream.Close();
            }
        }
    }