Is there a way of manipulating zip file contents in memory with Powershell?

Question

I\'m currently trying to write a powershell function which works with the output of the Lync powershell cmdlet \"Export-CsConfiguration -AsBytes\". When using implicit Power

Answer 1

Answering my own question here, in case it proves useful to others: (N.B. Requires .NET 4.5)

It looks like using System.IO.Compression.ZipArchive in combination with System.IO.Memorystream is the way forward. I've got this now:

Function Load-CsConfig{
  [System.Reflection.Assembly]::LoadWithPartialName('System.IO.Compression') | Out-Null

  $ZipBytes = Export-CsConfiguration -AsBytes
  $ZipStream = New-Object System.IO.Memorystream
  $ZipStream.Write($ZipBytes,0,$ZipBytes.Length)
  $ZipArchive = New-Object System.IO.Compression.ZipArchive($ZipStream)
  $ZipEntry = $ZipArchive.GetEntry('DocItemSet.xml')
  $EntryReader = New-Object System.IO.StreamReader($ZipEntry.Open())
  $DocItemSet = $EntryReader.ReadToEnd()
  return $DocItemSet
}

Which does exactly what I need.

Thanks all :)

Answer 2

Making the "Made up Powershell function" a reality:

#
#   .SYNOPSIS
#       Extract a file from a byte[] zip file
#   
#   .DESCRIPTION
#       Extracts a file from a byte[] zip file as byte[]
#   
#   .PARAMETER ByteArray
#       Byte array containing zip file
#   
#   .PARAMETER FileInsideZipIWant
#       The file inside zip I want
#   
#   .PARAMETER utf8
#       If the file is UTF-8 encoded, use this switch to get a string
#   
#   .EXAMPLE
#       PS C:\> $utf8str = Extract-FileFromInMemoryZip -ByteArray $ZipFileBytes -FileInsideZipIWant "DocItemSet.xml" -utf8
#       PS C:\> $utf8str = Extract-FileFromInMemoryZip $ZipFileBytes "DocItemSet.xml" -utf8
#       PS C:\> $bs = Extract-FileFromInMemoryZip $ZipFileBytes "DocItemSet.xml"        
#   
#   .OUTPUTS
#       string, byte[]
#   
#   .NOTES
#       Exactly as desired. You may want to change the name of the "FileInsideZipIWant" parameter.
#       Don't plan on extracting files larger than 2GB.
#
function Extract-FileFromInMemoryZip
{
    [CmdletBinding(DefaultParameterSetName = 'raw')]
    [OutputType([string], ParameterSetName = 'utf8')]
    [OutputType([byte[]], ParameterSetName = 'raw')]
    param
    (
        [Parameter(Mandatory, ValueFromPipelineByPropertyName, Position = 0,
                   HelpMessage = 'Byte array containing zip file')]
        [byte[]]$ByteArray,
        [Parameter(Mandatory, ValueFromPipelineByPropertyName, Position = 1,
                   HelpMessage = 'Single file to extract')]
        [string]$FileInsideZipIWant,
        [Parameter(ParameterSetName = 'utf8')]
        [switch]$utf8
    )

    BEGIN { Add-Type -AN System.IO.Compression -ea:Stop } # Stop on error

    PROCESS {
        $entry = (
            New-Object System.IO.Compression.ZipArchive(
                New-Object System.IO.MemoryStream ( ,$ByteArray)
            )
        ).GetEntry($FileInsideZipIWant)

        # Note ZipArchiveEntry.Length returns a long (rather than int),
        # but we can't conveniently construct arrays longer than System.Int32.MaxValue
        $b = [byte[]]::new($entry.Length)

        # Avoid StreamReader to (dramatically) improve performance
        # ...but it may be useful if the extracted file has a BOM header
        $entry.Open().Read($b, 0, $b.Length)

        write $(
            if ($utf8) { [System.Text.Encoding]::UTF8.GetString($b) }
            else { $b }
        )
    }
}

Answer 3

DotNetZip is your friend. This SO post reads from a stream, but it's C# code.

The code below is PowerShell, but is untested. However, it should hopefully be a good starting point for you. You should get intellisense on the DotNetZip objects and there is tons of help and example code on their website.

#load the DotNetZip assembly from disk and create a new zip object
[System.Reflection.Assembly]::LoadFrom("C:\Path\To\Ionic.Zip.dll")
$zipfile = New-Object Ionic.Zip.ZipFile

#your stream
$ZipFileBytes = Export-CsConfiguration -AsBytes

#your filename
$filename = "DocItemSet.xml"

$zipfile.Read($ZipFileBytes)
$file = $zipfile[$filename]

$stream = $file.OpenReader()

$buffer = New-Object Byte[] 4096
[int]$n

[string]$xmlFile = ""

cls
do {
  $n = $stream.Read($buffer,0, $buffer.Length);
  $totalBytesRead+=$n;
  $xmlFile += [System.Text.Encoding]::ASCII.GetString($buffer)
} while ($n -gt 0);

$stream.Close()
$stream.Dispose()
$zipfile.Dispose()