ForwardOrReverse

# TODO: Use buffering to see if performance can be improved.
function Gzip-FileSimple
{
    param
    (
        [String]$inFile = $(throw "Gzip-File: No filename specified"),
        [String]$outFile = $($inFile + ".gz"),
        [switch]$delete # Delete the original file
    )
 
    trap
    {
        Write-Host "Received an exception: $_.  Exiting."
        break
    }
 
    if (! (Test-Path $inFile))
    {
        "Input file $inFile does not exist."
        exit 1
    }
 
    Write-Host "Compressing $inFile to $outFile."
 
    $input = New-Object System.IO.FileStream $inFile, ([IO.FileMode]::Open), ([IO.FileAccess]::Read), ([IO.FileShare]::Read)
 
    $buffer = New-Object byte[]($input.Length)
    $byteCount = $input.Read($buffer, 0, $input.Length)
 
    if ($byteCount -ne $input.Length)
    {
        $input.Close()
        Write-Host "Failure reading $inFile."
        exit 2
    }
    $input.Close()
 
    $output = New-Object System.IO.FileStream $outFile, ([IO.FileMode]::Create), ([IO.FileAccess]::Write), ([IO.FileShare]::None)
    $gzipStream = New-Object System.IO.Compression.GzipStream $output, ([IO.Compression.CompressionMode]::Compress)
 
    $gzipStream.Write($buffer, 0, $buffer.Length)
    $gzipStream.Close()
 
    $output.Close()
 
    if ($delete)
    {
        Remove-Item $inFile
    }
}

Get-VM | ForEach-Object {
    $vmname = $_.Name
    $_.HardDisks | Select-Object @{Name="VM"; Expression={$vmname}}, Filename, Persistence
}

# Find the date of a previous weekday.  Originally conceived to export performance
# from a give day of the week no matter when it was called.
function Get-PreviousWeekdayDate
{
    param
    (
        [DateTime]$date = $(Get-Date),
        [System.DayOfWeek]$weekDay = $([System.DayOfWeek]::Sunday),  # Full weekday names work here.
        [switch]$fullWeek # The return date must be a full week ago.
    )
 
    Set-Variable -Name DAYS_IN_WEEK -Value 7 -Option Constant
 
    $dayDelta = 0 # The difference in days between $date and the target day.
 
    # If we are further in the week then we just go back x days.
    if ([Int32]$date.DayOfWeek -ge [Int32]$weekDay)
    {
        $dayDelta = [Int32]$date.DayOfWeek - [Int32]$weekDay
    }
    # Otherwise we need wrap around the week
    else
    {
        $dayDelta = $DAYS_IN_WEEK + [Int32]$date.DayOfWeek - [Int32]$weekDay
    }
 
    $date = $date.AddDays(-$dayDelta)
 
    # Go back 7 days 
    if ($fullWeek)
    {
        $date = $date.AddDays(-$DAYS_IN_WEEK)
    }
 
    $date
}