?using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.IO.Compression;

namespace zip
{
    public static class zip
    {
        //static 才能被類直接引用，而不需要實例化對象
        public static  byte[] Compress(byte[] data)
        {
            MemoryStream ms = new MemoryStream();
            Stream zipStream;
            zipStream = new GZipStream(ms, CompressionMode.Compress, true);
            zipStream.Write(data, 0, data.Length);   //將數據data壓縮后引進了ms中
            zipStream.Close();

            byte[] compress_data = new byte[ms.Length];
            ms.Read(compress_data, 0, int.Parse(ms.Length.ToString())); //將ms中的流讀到compress_data中
            ms.Close();
            return compress_data;

        }

        /// <summary>
        /// Decompresses the specified data.
        /// </summary>
        /// <param name="data">The data.</param>
        /// <returns></returns>
        public static byte[] Decompress(byte[] data)
        {
            try
            {
                MemoryStream ms = new MemoryStream(data);
                Stream zipStream = null;
                zipStream = new GZipStream(ms, CompressionMode.Decompress);
                byte[] dc_data = null;
                dc_data = EtractBytesFormStream(zipStream, data.Length);
                return dc_data;
            }
            catch
            {
                return null;
            }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="zipStream"></param>
        /// <param name="dataBlock">接受data.length</param>
        /// <returns></returns>
        public static byte[] EtractBytesFormStream(Stream zipStream, int dataBlock)
        {
            try
            {
                byte[] data = null;
                int totalBytesRead = 0;
                while (true)
                {
                    Array.Resize(ref data, totalBytesRead + dataBlock + 1);
                    int bytesRead = zipStream.Read(data, totalBytesRead, dataBlock);
                    if (bytesRead == 0)
                    {
                        break;
                    }
                    totalBytesRead += bytesRead;
                }
                Array.Resize(ref data, totalBytesRead);
                return data;
            }
            catch
            {
                return null;
            }
        }
    }
}