using System.IO;
using System.IO.Compression;

namespace AllBase
{
    public static class ZipHelper
    {
        /// <summary>
        /// GZip压缩
        /// </summary>
        /// <param name="rawData"></param>
        /// <returns></returns>
        public static byte[] Compress(byte[] rawData)
        {
            if (rawData == null || rawData.Length < 1000)
                return rawData;
            MemoryStream ms = new MemoryStream();
            GZipStream compressedzipStream = new GZipStream(ms, CompressionMode.Compress, true);
            compressedzipStream.Write(rawData, 0, rawData.Length);
            compressedzipStream.Close();
            return ms.ToArray();
        }

        /// <summary>
        /// ZIP解压
        /// </summary>
        /// <param name="zippedData"></param>
        /// <returns></returns>
        public static byte[] Decompress(byte[] zippedData)
        {
            if (zippedData == null || zippedData.Length == 0)
                return null;
            if (zippedData.Length < 100)
                return zippedData;
            if (zippedData[2] != 0x8 || zippedData[3] != 0x0 || zippedData[4] != 0x0 
                || zippedData[5] != 0x0 || zippedData[6] != 0x0 || zippedData[7] != 0x0
                || zippedData[0] != 31 || zippedData[1] != 139)//软加速判断头尾是否正确
                return zippedData;
            try
            {
                MemoryStream ms = new MemoryStream(zippedData);
                GZipStream compressedzipStream = new GZipStream(ms, CompressionMode.Decompress);
                MemoryStream outBuffer = new MemoryStream();
                byte[] block = new byte[1024];
                while (true)
                {
                    int bytesRead = compressedzipStream.Read(block, 0, block.Length);
                    if (bytesRead < 1)
                        break;
                    outBuffer.Write(block, 0, bytesRead);
                }
                compressedzipStream.Close();
                return outBuffer.ToArray();
            }
            catch
            {
            }
            return zippedData;
        }
    }
}