Victor Maceda’s Technical Blog

Imports System.IO
Imports System.IO.Compression

Public Class ZipUtil

    Public Sub CompressFile(ByVal sourceFile As String, ByVal destinationFile As String)

        ' make sure the source file is there
        If File.Exists(sourceFile) = False Then
            Throw New FileNotFoundException
        End If

        ' Create the streams and byte arrays needed
        Dim buffer As Byte() = Nothing
        Dim sourceStream As FileStream = Nothing
        Dim destinationStream As FileStream = Nothing
        Dim compressedStream As GZipStream = Nothing

        Try
            ' Read the bytes from the source file into a byte array
            sourceStream = New FileStream(sourceFile, FileMode.Open, FileAccess.Read, FileShare.Read)

            ' Read the source stream values into the buffer
            buffer = New Byte(sourceStream.Length) {}
            Dim checkCounter As Integer = sourceStream.Read(buffer, 0, buffer.Length)

            ' Open the FileStream to write to
            destinationStream = New FileStream(destinationFile, FileMode.OpenOrCreate, FileAccess.Write)

            ' Create a compression stream pointing to the destiantion stream
            compressedStream = New GZipStream(destinationStream, CompressionMode.Compress, True)

            'Now write the compressed data to the destination file
            compressedStream.Write(buffer, 0, buffer.Length)

        Catch ex As ApplicationException
            MessageBox.Show(ex.Message, "An Error occured during compression", MessageBoxButtons.OK, MessageBoxIcon.Error)
        Finally
            ' Make sure we allways close all streams
            If Not (sourceStream Is Nothing) Then
                sourceStream.Close()
            End If
            If Not (compressedStream Is Nothing) Then
                compressedStream.Close()
            End If
            If Not (destinationStream Is Nothing) Then
                destinationStream.Close()
            End If
        End Try

    End Sub

    Public Sub DecompressFile(ByVal sourceFile As String, ByVal destinationFile As String)

        ' make sure the source file is there
        If File.Exists(sourceFile) = False Then
            Throw New FileNotFoundException
        End If

        ' Create the streams and byte arrays needed
        Dim sourceStream As FileStream = Nothing
        Dim destinationStream As FileStream = Nothing
        Dim decompressedStream As GZipStream = Nothing
        Dim quartetBuffer As Byte() = Nothing

        Try
            ' Read in the compressed source stream
            sourceStream = New FileStream(sourceFile, FileMode.Open)

            ' Create a compression stream pointing to the destiantion stream
            decompressedStream = New GZipStream(sourceStream, CompressionMode.Decompress, True)

            ' Read the footer to determine the length of the destiantion file
            quartetBuffer = New Byte(4) {}
            Dim position As Integer = CType(sourceStream.Length, Integer) - 4
            sourceStream.Position = position
            sourceStream.Read(quartetBuffer, 0, 4)
            sourceStream.Position = 0
            Dim checkLength As Integer = BitConverter.ToInt32(quartetBuffer, 0)

            Dim buffer(checkLength + 100) As Byte
            Dim offset As Integer = 0
            Dim total As Integer = 0

            ' Read the compressed data into the buffer
            While True
                Dim bytesRead As Integer = decompressedStream.Read(buffer, offset, 100)
                If bytesRead = 0 Then
                    Exit While
                End If
                offset += bytesRead
                total += bytesRead
            End While

            ' Now write everything to the destination file
            destinationStream = New FileStream(destinationFile, FileMode.Create)
            destinationStream.Write(buffer, 0, total)

            ' and flush everyhting to clean out the buffer
            destinationStream.Flush()

        Catch ex As ApplicationException
            MessageBox.Show(ex.Message, "An Error occured during compression", MessageBoxButtons.OK, MessageBoxIcon.Error)
        Finally
            ' Make sure we allways close all streams
            If Not (sourceStream Is Nothing) Then
                sourceStream.Close()
            End If
            If Not (decompressedStream Is Nothing) Then
                decompressedStream.Close()
            End If
            If Not (destinationStream Is Nothing) Then
                destinationStream.Close()
            End If
        End Try

    End Sub

End Class