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Imports System
Imports System.Collections.Generic
Imports System.IO
Imports System.IO.Compression
' 此类是一个读取器，它会读取文件基底数据流以便一个接着一个取得压缩文件中项目。
' 压缩文件项目内含文件名称、大小、压缩后的大小、CRC...等信息。
' 它同时支持 GZIP 与 DEFLATE 这两种压缩方式。
Public Class ZipReader '更多.net源码和教程，来自[乐博网 www.lob.cn]
' 此封存数据流会在每一次操作之后被初始化与关闭。
Private zipStream As Stream
' 封存的名称。
Private zipName As String
' 被读取之标头与压缩数据的数据流。
Private baseStream As Stream
Private numberOfFiles As Int16
Private thisMethod As Byte
Private md5 As System.Security.Cryptography.MD5CryptoServiceProvider
' 用于检查 CRC 。
' 建立一个新的封存输入数据流，读取一个压缩文件。
Public Sub New(ByVal fileStream As Stream, ByVal name As String)
zipName = name
baseStream = fileStream
numberOfFiles = -1
thisMethod = 255
md5 = New System.Security.Cryptography.MD5CryptoServiceProvider()
End Sub 'New
' 读取超标头。
' 超标头结构：
' 文件的数目 - 2 字节
' 压缩的方式 - 1 字节
Private Sub ReadSuperHeader()
numberOfFiles = ReadLeInt16()
thisMethod = ReadLeByte()
If Method <> ZipConstants.DEFLATE AndAlso Method <> ZipConstants.GZIP Then
Throw New ArgumentOutOfRangeException()
End If
End Sub 'ReadSuperHeader
Private Function ReadBuf(ByVal outBuf() As Byte, ByVal length As Integer) As Integer
Return baseStream.Read(outBuf, 0, length)
End Function 'ReadBuf
' 从 baseStream 读取一个字节。
Private Function ReadLeByte() As Byte
Return System.Convert.ToByte(baseStream.ReadByte() And &HFF)
End Function 'ReadLeByte
' 以小尾序（Little-Endian）字节顺序来读取一个不带符号的 short 基础数据流。
Private Function ReadLeInt16() As Int16
Dim i As Int16 = CType(ReadLeByte(), Int16)
Dim j As Int16 = CType(ReadLeByte(), Int16)
Return (i Or (j << 8))
End Function 'ReadLeInt16
' 以小尾序（Little-Endian）字节顺序来读取一个 int 基底数据流。
Private Function ReadLeInt32() As Int32
Dim ui As Int32
Dim uj As Int32
ui = CType(ReadLeInt16(), Int32)
uj = CType(ReadLeInt16(), Int32)
If (ui < 0) Then
ui = System.Math.Pow(2, 16) + ui
End If
Return (ui Or (uj << 16))
End Function 'ReadLeInt32
Private Function ConvertToString(ByVal data() As Byte) As String
Return System.Text.Encoding.ASCII.GetString(data, 0, data.Length)
End Function 'ConvertToString
' 从压缩文件读取下一个项目并返回其描述。
Private Function GetNextEntry() As ZipEntry
Dim currentEntry As ZipEntry = Nothing
Try
Dim size As Int32 = ReadLeInt32()
If size = -1 Then
Return New ZipEntry(String.Empty)
End If
Dim csize As Int32 = ReadLeInt32()
Dim crc(15) As Byte
ReadBuf(crc, crc.Length)
Dim dostime As Int32 = ReadLeInt32()
Dim nameLength As Int16 = ReadLeInt16()
Dim buffer(nameLength - 1) As Byte
ReadBuf(buffer, nameLength)
Dim name As String = ConvertToString(buffer)
currentEntry = New ZipEntry(name)
currentEntry.Size = size
currentEntry.CompressedSize = csize
currentEntry.SetCrc(crc)
currentEntry.DosTime = dostime
Catch ex As ArgumentException
ZipConstants.ShowError(ZipConstants.ArgumentError)
Catch ex As ObjectDisposedException
ZipConstants.ShowError(ZipConstants.CloseError)
End Try
Return currentEntry
End Function 'GetNextEntry
' 将未压缩数据写入项目中的文件名称。
' 它会初始化一个内存数据流来作为暂存处，并且使用 Gzip 数据流
' 或 Deflate 数据流来解压缩它。
Private Sub WriteUncompressedFile(ByVal entry As ZipEntry, ByVal completePath As String)
Dim ms As New MemoryStream()
Try
Dim b(entry.CompressedSize - 1) As Byte
baseStream.Read(b, 0, CType(entry.CompressedSize, Integer))
If CheckCRC(entry.GetCrc(), b) Then
ms.Write(b, 0, b.Length)
End If
ms.Seek(0, SeekOrigin.Begin)
If Method = ZipConstants.DEFLATE Then
zipStream = New DeflateStream(ms, CompressionMode.Decompress, False)
ElseIf Method = ZipConstants.GZIP Then
zipStream = New GZipStream(ms, CompressionMode.Decompress, False)
End If
Dim index As Integer = entry.Name.LastIndexOf(ZipConstants.BackSlash)
Dim name As String = completePath + entry.Name.Substring(index + 1)
Dim rewrite As New FileStream(name, FileMode.Create)
b = New Byte(entry.Size - 1) {}
zipStream.Read(b, 0, CType(entry.Size, Integer))
rewrite.Write(b, 0, CType(entry.Size, Integer))
rewrite.Close()
Catch ex As IOException
ZipConstants.ShowError(ZipConstants.IOError)
Catch ex As ArgumentException
ZipConstants.ShowError(ZipConstants.ArgumentError)
Finally
zipStream.Close()
ms.Close()
End Try
End Sub 'WriteUncompressedFile
' 解压缩清单中的所有项目。
' 清单可能是空的。
Public Sub ExtractAll(ByVal zipEntries As List(Of ZipEntry), _
ByVal startPath As String)
Try
Dim dir As New DirectoryInfo(startPath + zipName)
If Not dir.Exists Then
dir.Create()
End If
Dim jump As Integer = 3
baseStream.Seek(jump, SeekOrigin.Begin)
Dim entry As ZipEntry
For Each entry In zipEntries
Dim index1 As Integer = entry.Name.IndexOf(ZipConstants.BackSlash)
Dim index2 As Integer = entry.Name.LastIndexOf(ZipConstants.BackSlash)
Dim relPath As String = entry.Name.Substring(index1 + 1, index2 - index1)
If index1 = 0 Then
relPath = String.Empty
End If
If relPath.Length <> 0 Then
dir.CreateSubdirectory(relPath)
End If
jump = ZipConstants.FixedHeaderSize + entry.NameLength
baseStream.Seek(jump, SeekOrigin.Current)
WriteUncompressedFile(entry, startPath + zipName + ZipConstants.BackSlash + relPath)
Next entry
CH2_DemoForm002.statusMessage = String.Format(System.Threading.Thread.CurrentThread.CurrentUICulture, ZipConstants.ExtractMessage, startPath + zipName + ZipConstants.BackSlash)
Catch ex As IOException
ZipConstants.ShowError(ZipConstants.IOError)
Catch ex As OutOfMemoryException
ZipConstants.ShowError(ZipConstants.MemoryError)
End Try
End Sub
' 解压缩指定的项目。
Public Sub Extract(ByVal entry As ZipEntry, ByVal jump As Long, ByVal startPath As String)
Try
Dim dir As New DirectoryInfo(startPath + zipName)
If Not dir.Exists Then
dir.Create()
End If
Dim index1 As Integer = entry.Name.IndexOf(ZipConstants.BackSlash)
Dim index2 As Integer = entry.Name.LastIndexOf(ZipConstants.BackSlash)
Dim relPath As String = entry.Name.Substring(index1 + 1, index2 - index1)
If index1 = 0 Then
relPath = String.Empty
End If
If relPath.Length <> 0 Then
dir.CreateSubdirectory(relPath)
End If
baseStream.Seek(jump, SeekOrigin.Begin)
jump = ZipConstants.FixedHeaderSize + entry.NameLength
baseStream.Seek(jump, SeekOrigin.Current)
WriteUncompressedFile(entry, startPath + zipName + ZipConstants.BackSlash + relPath)
CH2_DemoForm002.statusMessage = String.Format(System.Threading.Thread.CurrentThread.CurrentUICulture, ZipConstants.ExtractMessage, startPath + zipName + ZipConstants.BackSlash)
Catch ex As IOException
ZipConstants.ShowError(ZipConstants.IOError)
Catch ex As OutOfMemoryException
ZipConstants.ShowError(ZipConstants.MemoryError)
End Try
End Sub
' 取得文件中的所有项目。
Public Function GetAllEntries() As List(Of ZipEntry)
Dim headers As List(Of ZipEntry)
headers = Nothing
Try
If thisMethod = 255 OrElse numberOfFiles = -1 Then
baseStream.Seek(0, SeekOrigin.Begin)
ReadSuperHeader()
End If
headers = New List(Of ZipEntry)(numberOfFiles)
baseStream.Seek(3, SeekOrigin.Begin)
Dim i As Integer
While i < numberOfFiles
Dim entry As ZipEntry = GetNextEntry()
headers.Add(entry)
baseStream.Seek(entry.CompressedSize, SeekOrigin.Current)
i += 1
End While
Catch ex As IOException
ZipConstants.ShowError(ZipConstants.IOError)
End Try
Return headers
End Function
' 取得封存档的压缩方式。
Public ReadOnly Property Method() As Byte
Get
Return thisMethod
End Get
End Property '更多.net源码和教程，来自[乐博网 www.lob.cn]
' 检查字节数组的 CRC。
Private Function CheckCRC(ByVal crc As Byte(), ByVal data As Byte()) As Boolean
Dim newCrc As Byte() = md5.ComputeHash(data)
Dim i As Integer
While i < crc.Length
If crc(i) <> newCrc(i) Then
Return False
End If
i += 1
End While
Return True
End Function 'CheckCRC
End Class 'ZipReader
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