压缩和编码字符串丢弃最后两个字节答案

【问题标题】：Compress and encode string dropping last two bytes压缩和编码字符串丢弃最后两个字节
【发布时间】：2016-09-30 18:25:05
【问题描述】：

我有一个 VB.NET 应用程序，它生成一个 XML 文档，我需要将它发布到 Web 应用程序。在发布 XML 之前，我需要压缩 XML 并对其进行 base64 编码。下面我有一个代码 sn-p，我在其中获取一个 XML 字符串，使用 gzip 压缩，然后使用 base64 编码。为了确保我所做的事情是正确的，我将解码 base64，然后 gzip 解压缩。解压后，原始 XML 比我测试的 XML 长 2 个字节。我正在某处删除最后 2 个字节。他们去哪儿了？

    Dim xml As String = ds.ToXMLString()

    ' compress and encode
    Dim ceb() As Byte = System.Text.Encoding.UTF8.GetBytes(xml)
    Dim cems As New System.IO.MemoryStream()
    Dim cegz As New System.IO.Compression.GZipStream(cems, IO.Compression.CompressionMode.Compress)
    cegz.Write(ceb, 0, ceb.Length)
    Dim cees As String = System.Convert.ToBase64String(cems.ToArray())

    ' i want to make sure everything is working,
    ' decode and decompress and make sure it matches
    Dim ddb() As Byte = System.Convert.FromBase64String(cees)
    Dim ddms As New System.IO.MemoryStream(ddb)
    Dim ddgz As New System.IO.Compression.GZipStream(ddms, IO.Compression.CompressionMode.Decompress)
    Dim ddms2 As New System.IO.MemoryStream()
    ddgz.CopyTo(ddms2)

    Dim xmlRestored As String = System.Text.Encoding.UTF8.GetString(ddms2.ToArray())

    Assert.AreEqual(xml.Substring(0, xmlRestored.Length), xmlRestored) ' <-- SUCCESS
    Assert.AreEqual(xml.Length, xmlRestored.Length) ' <-- FAILS; xml.length=147802; xmlRestored.length=147800;

【问题讨论】：

标签： .net vb.net

【解决方案1】：

没关系。我没有关闭我的压缩流。应该是这样的：

Dim xml As String = ds.ToXMLString()

' compress and encode
Dim ceb() As Byte = System.Text.Encoding.UTF8.GetBytes(xml)
Dim cems As New System.IO.MemoryStream()
Dim cegz As New System.IO.Compression.GZipStream(cems, IO.Compression.CompressionMode.Compress)
cegz.Write(ceb, 0, ceb.Length)

' i was missing the closing of the gzip stream
cegz.Close()

Dim cees As String = System.Convert.ToBase64String(cems.ToArray())

' i want to make sure everything is working,
' decode and decompress and make sure it matches
Dim ddb() As Byte = System.Convert.FromBase64String(cees)
Dim ddms As New System.IO.MemoryStream(ddb)
Dim ddgz As New System.IO.Compression.GZipStream(ddms, IO.Compression.CompressionMode.Decompress)
Dim ddms2 As New System.IO.MemoryStream()
ddgz.CopyTo(ddms2)

Dim xmlRestored As String = System.Text.Encoding.UTF8.GetString(ddms2.ToArray())

Assert.AreEqual(xml, xmlRestored) ' <-- SUCCESS
Assert.AreEqual(xml.Length, xmlRestored.Length) ' <-- SUCCESS

【讨论】：