TruncateBytesScript

#Source Path (Change this string to the folder path containing the files you want to truncate)
$SOURCEPATH = "C:\Users\Downloads\DataFiles\SourceFolder"

#Destination Path (Change this string to the new folder path where you want to save the truncated files)
$DESTINATIONPATH = "C:\Users\Downloads\DataFiles\DestinationFolder"

$files = dir $SOURCEPATH | where { !$_.PsIsContainer }
$total = (Get-ChildItem $SOURCEPATH -File | Measure-Object).Count
$count = 1

if (!(Test-Path $DESTINATIONPATH -PathType Container)) {
    New-Item -ItemType Directory -Force -Path $DESTINATIONPATH
}

foreach ($file in $files) {
    Write-Output "File being truncated: $($file.FullName)"
	# Read the entire file content as a [byte[]] array.
	$byteArray = Get-Content "$($file.FullName)" -Raw -Encoding Byte

	# Convert the byte array to a single-line "byte string", where the whitespace-separated tokens are the hex encoding of a single byte.
	# If you prefer each byte to be consistently represented as two hex digits, even for values less than 0x10, (e.g., 01 rather than 1 or 00 rather than 0), use 'X2'
	$byteString = $byteArray.ForEach('ToString', 'X') -join ' '

	# Replacement Function (Change 42 59 54 45 53 54 52 49 4E 47 0 0 0 0 to your own specific byte string)
	# If you use 'X' above, hex numbers must not have leadig zeros (eg. 0 rather than 00)
	# If you use 'X2' above, hex numbers must have leadig zeros (eg. 09 rather than 9)
	$byteString = $byteString -replace '(?s)^.*(?=42 59 54 45 53 54 52 49 4E 47 0 0 0 0.*$)'

	# Convert the byte string back to a [byte[]] array, and save it to the target file.
	[byte[]] $newByteArray = -split $byteString -replace '^', '0x'
	Set-Content -path "$($DESTINATIONPATH+$file.Name)" -Encoding Byte -Value $newByteArray

    Write-Output "Truncation done!`n"
	
	Write-Output $count/$total
	$count++
}