javascript中base64和Gzip的使用

一般的使用流程（4步）：

服务器端将字符串Gzip压缩为 字节数组——>通过base64转为字符串（后传递到客户端）——>解码base64字符串为字节数组——>Gzip解码字节数组为可用字符串。

第一步：服务器端压缩（本人使用的是C#)

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Json;
using System.Text;
using System.Web;
using ICSharpCode.SharpZipLib.BZip2;
using ICSharpCode.SharpZipLib.GZip;
using ICSharpCode.SharpZipLib.Zip;


namespace amtioth5.Helper
{
    public enum CompressionType
    {
        /// <summary>
        /// GZip 压缩格式
        /// </summary>
        GZip,
        /// <summary>
        /// BZip2 压缩格式
        /// </summary>
        BZip2,
        /// <summary>
        /// Zip 压缩格式
        /// </summary>
        Zip
    }

    public class CompressHelper
    {
        public static CompressionType CompressionProvider = CompressionType.GZip;

        #region Public methods

        /// <summary>
        /// 从原始字节数组生成已压缩的字节数组。
        /// </summary>
        /// <param name="bytesToCompress">原始字节数组。</param>
        /// <returns>返回已压缩的字节数组</returns>
        public static byte[] Compress(byte[] bytesToCompress)
        {
            MemoryStream ms = new MemoryStream();
            Stream s = OutputStream(ms);
            s.Write(bytesToCompress, 0, bytesToCompress.Length);
            s.Close();
            return ms.ToArray();
        }

        /// <summary>
        /// 从原始字符串生成已压缩的字符串。
        /// </summary>
        /// <param name="stringToCompress">原始字符串。</param>
        /// <returns>返回已压缩的字符串。</returns>
        public static string Compress(string stringToCompress)
        {
            byte[] compressedData = CompressToByte(stringToCompress);
            string strOut = Convert.ToBase64String(compressedData);
            return strOut;
        }

        /// <summary>
        /// 从原始字符串生成已压缩的字节数组。
        /// </summary>
        /// <param name="stringToCompress">原始字符串。</param>
        /// <returns>返回已压缩的字节数组。</returns>
        public static byte[] CompressToByte(string stringToCompress)
        {
            byte[] bytData = Encoding.UTF8.GetBytes(stringToCompress);
            return Compress(bytData);
        }

        /// <summary>
        /// 从已压缩的字符串生成原始字符串。
        /// </summary>
        /// <param name="stringToDecompress">已压缩的字符串。</param>
        /// <returns>返回原始字符串。</returns>
        public static string DeCompress(string stringToDecompress)
        {
            string outString = string.Empty;
            if (stringToDecompress == null)
            {
                throw new ArgumentNullException("stringToDecompress", "You tried to use an empty string");
            }

            try
            {
                byte[] inArr = Convert.FromBase64String(stringToDecompress.Trim());
                byte[] deArr = DeCompress(inArr);
                outString = Encoding.UTF8.GetString(deArr, 0, deArr.Length);
            }
            catch (NullReferenceException nEx)
            {
                return nEx.Message;
            }

            return outString;
        }

        /// <summary>
        /// 从已压缩的字节数组生成原始字节数组。
        /// </summary>
        /// <param name="bytesToDecompress">已压缩的字节数组。</param>
        /// <returns>返回原始字节数组。</returns>
        public static byte[] DeCompress(byte[] bytesToDecompress)
        {
            byte[] writeData = new byte[4096];
            Stream s2 = InputStream(new MemoryStream(bytesToDecompress));
            MemoryStream outStream = new MemoryStream();

            while (true)
            {
                int size = s2.Read(writeData, 0, writeData.Length);
                if (size > 0)
                {
                    outStream.Write(writeData, 0, size);
                }
                else
                {
                    break;
                }
            }
            s2.Close();
            byte[] outArr = outStream.ToArray();
            outStream.Close();
            return outArr;
        }

        #endregion

        #region Private methods

        /// <summary>
        /// 从给定的流生成压缩输出流。
        /// </summary>
        /// <param name="inputStream">原始流。</param>
        /// <returns>返回压缩输出流。</returns>
        private static Stream OutputStream(Stream inputStream)
        {
            switch (CompressionProvider)
            {
                case CompressionType.BZip2:
                    return new BZip2OutputStream(inputStream);

                case CompressionType.GZip:
                    return new GZipOutputStream(inputStream);

                case CompressionType.Zip:
                    return new ZipOutputStream(inputStream);

                default:
                    return new GZipOutputStream(inputStream);
            }
        }

        /// <summary>
        /// 从给定的流生成压缩输入流。
        /// </summary>
        /// <param name="inputStream">原始流。</param>
        /// <returns>返回压缩输入流。</returns>
        private static Stream InputStream(Stream inputStream)
        {
            switch (CompressionProvider)
            {
                case CompressionType.BZip2:
                    return new BZip2InputStream(inputStream);

                case CompressionType.GZip:
                    return new GZipInputStream(inputStream);

                case CompressionType.Zip:
                    return new ZipInputStream(inputStream);

                default:
                    return new GZipInputStream(inputStream);
            }
        }

        #endregion

        public static T FromJsonTo<T>(string jsonString)
        {

            DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(T));

            MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(jsonString));

            T jsonObject = (T)ser.ReadObject(ms);

            ms.Close();

            return jsonObject;
        }

        public static string ToJsonString(object item)
        {
            DataContractJsonSerializer serializer = new DataContractJsonSerializer(item.GetType());

            using (MemoryStream ms = new MemoryStream())
            {
                serializer.WriteObject(ms, item);

                StringBuilder sb = new StringBuilder();

                byte[] bytes = ms.ToArray();

                sb.Append(Encoding.UTF8.GetString(bytes, 0, bytes.Length));

                return sb.ToString();
            }
        }
    }
}

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