解码Base64和Inflate Zlib压缩XML

时间:2013-03-12 01:00:08

标签: c# json base64 zlib

对于这篇长篇文章感到抱歉,我会尽量缩短篇幅。

我正在使用json API(当然没有文档),它会返回如下内容:

{
uncompressedlength: 743637,
compressedlength: 234532,
compresseddata: "lkhfdsbjhfgdsfgjhsgfjgsdkjhfgj"
}

压缩数据(在这种情况下为xml),然后压缩我尝试提取的base64编码数据。我所拥有的只是用perl编写的演示代码来解码它:

use Compress::Zlib qw(uncompress);
use MIME::Base64  qw(decode_base64);
my $uncompresseddata = uncompress(decode_base64($compresseddata));

看起来很简单。

我尝试了很多方法来解码base64:

 private string DecodeFromBase64(string encodedData)
    {
        byte[] encodedDataAsBytes = System.Convert.FromBase64String(encodedData);
        string returnValue = System.Text.Encoding.Unicode.GetString(encodedDataAsBytes);
        return returnValue;
    }

    public string base64Decode(string data)
    {
        try
        {
            System.Text.UTF8Encoding encoder = new System.Text.UTF8Encoding();
            System.Text.Decoder utf8Decode = encoder.GetDecoder();

            byte[] todecode_byte = Convert.FromBase64String(data);
            int charCount = utf8Decode.GetCharCount(todecode_byte, 0, todecode_byte.Length);
            char[] decoded_char = new char[charCount];
            utf8Decode.GetChars(todecode_byte, 0, todecode_byte.Length, decoded_char, 0);
            string result = new String(decoded_char);
            return result;
        }
        catch (Exception e)
        {
            throw new Exception("Error in base64Decode" + e.Message);
        }
    }

我尝试过使用Ionic.Zip.dll(DotNetZip?)和zlib.net来扩充Zlib压缩。但是一切都错了。我试图找出问题的来源。它是base64解码还是Inflate?

使用zlib进行充气时总是出错:使用zlib.net时出现错误的Magic Number错误,使用DotNetZip时出现“Bad state(存储块长度无效)”:

string decoded = DecodeFromBase64(compresseddata);
string decompressed = UnZipStr(GetBytes(decoded));


 public static string UnZipStr(byte[] input)
    {

        using (MemoryStream inputStream = new MemoryStream(input))
        {
            using (Ionic.Zlib.DeflateStream zip =
              new Ionic.Zlib.DeflateStream(inputStream, Ionic.Zlib.CompressionMode.Decompress))
            {
                using (StreamReader reader =
                  new StreamReader(zip, System.Text.Encoding.UTF8))
                {
                    return reader.ReadToEnd();
                }
            }
        }
    }

看完之后: http://george.chiramattel.com/blog/2007/09/deflatestream-block-length-does-not-match.html 并听取其中一条评论。我将代码更改为:

MemoryStream memStream = new MemoryStream(Convert.FromBase64String(compresseddata));
memStream.ReadByte();
memStream.ReadByte();
DeflateStream deflate = new DeflateStream(memStream, CompressionMode.Decompress);
string doc = new StreamReader(deflate, System.Text.Encoding.UTF8).ReadToEnd();

它工作正常。

2 个答案:

答案 0 :(得分:3)

这是罪魁祸首:

http://george.chiramattel.com/blog/2007/09/deflatestream-block-length-does-not-match.html

通过跳过前两个字节,我可以将其简化为:

MemoryStream memStream = new MemoryStream(Convert.FromBase64String(compresseddata));
memStream.ReadByte();
memStream.ReadByte();
DeflateStream deflate = new DeflateStream(memStream, CompressionMode.Decompress);
string doc = new StreamReader(deflate, System.Text.Encoding.UTF8).ReadToEnd();

答案 1 :(得分:1)

首先,使用System.IO.Compression.DeflateStream重新充气数据。您应该能够使用MemoryStream作为输入流。您可以使用byte[]的{​​{1}}结果创建一个MemoryStream。

您可能会在尝试将base64结果转换为给定编码时遇到各种麻烦;直接使用原始数据进行Deflate。