Randomness #8
Description
I have the impression that your random generator is not really random.
The follow Powershell script uses a good random algorithm:
param(
[string]$SourceFolder = "M:\", # Source folder
[string]$DestinationFolder = "Q:\", # USB stick folder
[string[]]$Extensions = @("mp3","flac") # Extensions to include
)
# Ensure destination exists
if (-not (Test-Path $DestinationFolder)) {
New-Item -ItemType Directory -Path $DestinationFolder | Out-Null
}
# Collect all matching files recursively
$files = Get-ChildItem -Path $SourceFolder -Recurse -File |
Where-Object { $Extensions -contains $_.Extension.TrimStart(".").ToLower() }
if ($files.Count -eq 0) {
Write-Host "No files found with the specified extensions."
exit
}
# Get free space on destination drive (in bytes)
$driveLetter = (Get-Item $DestinationFolder).PSDrive.Name
$freeSpace = (Get-PSDrive -Name $driveLetter).Free
Write-Host "Free space on ${driveLetter}: $([math]::Round($freeSpace / 1GB,2)) GB"
# Strong random generator
$cryptoRand = [System.Security.Cryptography.RandomNumberGenerator]::Create()
function Get-RandomIndex($max) {
$bytes = New-Object byte[] 4
$cryptoRand.GetBytes($bytes)
$val = [BitConverter]::ToUInt32($bytes,0)
return ($val % $max)
}
# Shuffle files randomly
$shuffled = $files | Sort-Object { Get-RandomIndex $files.Count }
# Select files until free space is filled
$selected = @()
$totalSize = 0
foreach ($file in $shuffled) {
if ($totalSize + $file.Length -le $freeSpace) {
$selected += $file
$totalSize += $file.Length
} else {
break
}
}
# Copy into flat folder with progress output
try {
$i = 1
foreach ($file in $selected) {
$destPath = Join-Path $DestinationFolder $file.Name
Write-Host ("[{0}/{1}] Copying: {2}" -f $i, $selected.Count, $file.FullName)
Copy-Item -Path $file.FullName -Destination $destPath -Force
$i++
}
Write-Host "Copied $($selected.Count) random files using $([math]::Round($totalSize / 1GB,2)) GB of space."
}
catch [System.Management.Automation.PipelineStoppedException] {
Write-Host "Script interrupted by user. Exiting gracefully..."
}