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();
            }
        }
    }
}

http://icsharpcode.github.io/SharpZipLib/  (需要一个依赖库是开源的）

第二步：使用base64将压缩后的字节变为base64字符串 （Convert.ToBase64String();）

此转换为.net平台里面自带的函数。

第三部：客户端在Javascript中利用zip.js将base64字符串解码为压缩字节

var bytes = Base64.decodeToBytes(base_ut8);///important

上面代码将base_ut8变量中的字符串转为字节数组。

第四部：解压第三步得到的字节数组

// compressed = Array.<number> or Uint8Array
var gunzip = new Zlib.Gunzip(compressed);
var plain = gunzip.decompress();

下面我写的一个流程

document.write("<script src='../Gzip/base64.js'></script>");
document.write("<script src='../Gzip/zlib_and_gzip.min.js'></script>");
document.write("<script src='../Gzip/encoding-indexes.js'></script>");
document.write("<script src='../Gzip/encoding.js'></script>");
var GzipHelper={
    DeCompressGzip:function(base64str){
        if(base64str===null||base64str==='') return '';
        var bytes =  Base64.decodeToBytes(base64str);
        var  gunzip  =  new  Zlib.Gunzip ( bytes );
        var plain = gunzip.decompress();
        var asciistring = new TextDecoder("utf-8").decode(plain);
        return asciistring;
        
    },
    CompressGzip:function(jsonstr){        
    }
}

 相关文件下载链接: http://pan.baidu.com/s/1jING8Hw 密码: erap

base64的转码和解码

/**
* UTF16和UTF8转换对照表
* U+00000000 – U+0000007F   0xxxxxxx
* U+00000080 – U+000007FF   110xxxxx 10xxxxxx
* U+00000800 – U+0000FFFF   1110xxxx 10xxxxxx 10xxxxxx
* U+00010000 – U+001FFFFF   11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
* U+00200000 – U+03FFFFFF   111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
* U+04000000 – U+7FFFFFFF   1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
*/
var Base64 = {
    // 转码表
    table : [
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
            'I', 'J', 'K', 'L', 'M', 'N', 'O' ,'P',
            'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
            'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
            'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
            'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
            'w', 'x', 'y', 'z', '0', '1', '2', '3',
            '4', '5', '6', '7', '8', '9', '+', '/',
        '='
    ],
    UTF16ToUTF8 : function(str) {
        var res = [], len = str.length;
        for (var i = 0; i < len; i++) {
            var code = str.charCodeAt(i);
            if (code > 0x0000 && code <= 0x007F) {
                // 单字节，这里并不考虑0x0000，因为它是空字节
                // U+00000000 – U+0000007F  0xxxxxxx
                res.push(str.charAt(i));
            } else if (code >= 0x0080 && code <= 0x07FF) {
                // 双字节
                // U+00000080 – U+000007FF  110xxxxx 10xxxxxx
                // 110xxxxx
                var byte1 = 0xC0 | ((code >> 6) & 0x1F);
                // 10xxxxxx
                var byte2 = 0x80 | (code & 0x3F);
                res.push(
                    String.fromCharCode(byte1), 
                    String.fromCharCode(byte2)
                );
            } else if (code >= 0x0800 && code <= 0xFFFF) {
                // 三字节
                // U+00000800 – U+0000FFFF  1110xxxx 10xxxxxx 10xxxxxx
                // 1110xxxx
                var byte1 = 0xE0 | ((code >> 12) & 0x0F);
                // 10xxxxxx
                var byte2 = 0x80 | ((code >> 6) & 0x3F);
                // 10xxxxxx
                var byte3 = 0x80 | (code & 0x3F);
                res.push(
                    String.fromCharCode(byte1), 
                    String.fromCharCode(byte2), 
                    String.fromCharCode(byte3)
                );
            } else if (code >= 0x00010000 && code <= 0x001FFFFF) {
                // 四字节
                // U+00010000 – U+001FFFFF  11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else if (code >= 0x00200000 && code <= 0x03FFFFFF) {
                // 五字节
                // U+00200000 – U+03FFFFFF  111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else /** if (code >= 0x04000000 && code <= 0x7FFFFFFF)*/ {
                // 六字节
                // U+04000000 – U+7FFFFFFF  1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            }
        }
 
        return res.join('');
    },
    UTF8ToUTF16 : function(str) {
        var res = [], len = str.length;
        var i = 0;
        for (var i = 0; i < len; i++) {
            var code = str.charCodeAt(i);
            // 对第一个字节进行判断
            if (((code >> 7) & 0xFF) == 0x0) {
                // 单字节
                // 0xxxxxxx
                res.push(str.charAt(i));
            } else if (((code >> 5) & 0xFF) == 0x6) {
                // 双字节
                // 110xxxxx 10xxxxxx
                var code2 = str.charCodeAt(++i);
                var byte1 = (code & 0x1F) << 6;
                var byte2 = code2 & 0x3F;
                var utf16 = byte1 | byte2;
                res.push(Sting.fromCharCode(utf16));
            } else if (((code >> 4) & 0xFF) == 0xE) {
                // 三字节
                // 1110xxxx 10xxxxxx 10xxxxxx
                var code2 = str.charCodeAt(++i);
                var code3 = str.charCodeAt(++i);
                var byte1 = (code << 4) | ((code2 >> 2) & 0x0F);
                var byte2 = ((code2 & 0x03) << 6) | (code3 & 0x3F);
                var utf16 = ((byte1 & 0x00FF) << 8) | byte2
                res.push(String.fromCharCode(utf16));
            } else if (((code >> 3) & 0xFF) == 0x1E) {
                // 四字节
                // 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else if (((code >> 2) & 0xFF) == 0x3E) {
                // 五字节
                // 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else /** if (((code >> 1) & 0xFF) == 0x7E)*/ {
                // 六字节
                // 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            }
        }
 
        return res.join('');
    },
    encode : function(str) {
        if (!str) {
            return '';
        }
        var utf8    = this.UTF16ToUTF8(str); // 转成UTF8
        var i = 0; // 遍历索引
        var len = utf8.length;
        var res = [];
        while (i < len) {
            var c1 = utf8.charCodeAt(i++) & 0xFF;
            res.push(this.table[c1 >> 2]);
            // 需要补2个=
            if (i == len) {
                res.push(this.table[(c1 & 0x3) << 4]);
                res.push('==');
                break;
            }
            var c2 = utf8.charCodeAt(i++);
            // 需要补1个=
            if (i == len) {
                res.push(this.table[((c1 & 0x3) << 4) | ((c2 >> 4) & 0x0F)]);
                res.push(this.table[(c2 & 0x0F) << 2]);
                res.push('=');
                break;
            }
            var c3 = utf8.charCodeAt(i++);
            res.push(this.table[((c1 & 0x3) << 4) | ((c2 >> 4) & 0x0F)]);
            res.push(this.table[((c2 & 0x0F) << 2) | ((c3 & 0xC0) >> 6)]);
            res.push(this.table[c3 & 0x3F]);
        }
 
        return res.join('');
    },
    decode : function(str) {
        if (!str) {
            return '';
        }
 
        var len = str.length;
        var i   = 0;
        var res = [];
 
        while (i < len) {
            code1 = this.table.indexOf(str.charAt(i++));
            code2 = this.table.indexOf(str.charAt(i++));
            code3 = this.table.indexOf(str.charAt(i++));
            code4 = this.table.indexOf(str.charAt(i++));
 
            c1 = (code1 << 2) | (code2 >> 4);
            c2 = ((code2 & 0xF) << 4) | (code3 >> 2);
            c3 = ((code3 & 0x3) << 6) | code4;
 
            res.push(String.fromCharCode(c1));
 
            if (code3 != 64) {
                res.push(String.fromCharCode(c2));
            }
            if (code4 != 64) {
                res.push(String.fromCharCode(c3));
            }
 
        }
 
        return this.UTF8ToUTF16(res.join(''));
    },
    decodeToBytes : function(str) {
        if (!str) {
            return '';
        }
 
        var len = str.length;
        var i   = 0;
        var res = [];
 
        while (i < len) {
            code1 = this.table.indexOf(str.charAt(i++));
            code2 = this.table.indexOf(str.charAt(i++));
            code3 = this.table.indexOf(str.charAt(i++));
            code4 = this.table.indexOf(str.charAt(i++));
 
            c1 = (code1 << 2) | (code2 >> 4);
            c2 = ((code2 & 0xF) << 4) | (code3 >> 2);
            c3 = ((code3 & 0x3) << 6) | code4; 
            res.push(c1);
            if (code2 != 64) {
                res.push(c2);
            }
            if (code3 != 64) {
                res.push(c3);
            }        
             
        }
        res.pop();
 
        return res;
    }
};
 

Gzip的转码和解码（zlib.js库）

https://github.com/imaya/zlib.js/blob/master/README.en.md

附带一个编码转换库（text-encoding）

https://github.com/inexorabletash/text-encoding