Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim fileStream As New FileStream(TextBox1.Text, FileMode.Open)

Dim buffer(fileStream.Length) As Byte

fileStream.Read(buffer, 0, CInt(fileStream.Length))

fileStream.Close()

fileStream = New FileStream(TextBox1.Text & ".zip", FileMode.Create)

Dim gZipStream As New Compression.GZipStream(fileStream, CompressionMode.Compress, False)

gZipStream.Write(buffer, 0, buffer.Length)

MessageBox.Show("圧縮完了")

End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

Dim file As String = TextBox1.Text

If Path.GetExtension(file) = ".zip" Then

Dim fileStream = New FileStream(file, FileMode.Open)

Dim gZipStream = New Compression.GZipStream(fileStream, CompressionMode.Decompress)

Dim tailleOctets(4) As Byte

Dim position As Integer = System.Convert.ToInt32(fileStream.Length - 4)

fileStream.Position = position

fileStream.Read(tailleOctets, 0, 4)

fileStream.Position = 0

Dim tailleFichier As Integer = BitConverter.ToInt32(tailleOctets, 0)

Dim buffer(tailleFichier + 100) As Byte

Dim monOffset As Integer = 0

Do

Dim decompressionOctets As Integer = gZipStream.Read(buffer, monOffset, 100)

If decompressionOctets = 0 Then

Exit Do

End If

monOffset += decompressionOctets

Loop

file = Microsoft.VisualBasic.Left(file, Len(file) - 4)

fileStream = New FileStream(file, FileMode.Create)

fileStream.Write(buffer, 0, tailleFichier - 1)

fileStream.Flush()

fileStream.Close()

gZipStream.Close()

MessageBox.Show("解凍完了")

Else

MessageBox.Show("解凍できません")

End If

End Sub