NES ROM UNHEADER (16 Byte Header Remover)

#nes_rom_unheader.ps1

# NES ROM UNHEADER (16 Byte Header Remover)
# -----------------------------------------
#
# ner0
# Created: 13/04/2020
# Reviewed: 14/04/2020
#
#
#
# Usage:
# 1. Place the script '#nes_rom_unheader.ps1' inside the same folder as your NES zipped ROMs
# 2. Open the command-line and change into the ROMs folder:
#		ex: cd /d "f:\my roms\nes"
# 3. Run the script:
#		ex: powershell.exe -ExecutionPolicy Bypass .\#nes_rom_unheader.ps1
#
#
# What does it do?
#   The script goes through all the zip files in your NES roms folder and extracts them,
#	  then it parses every unpacked ROM file and checks if it has the extra 16 byte header;
#	  if it does, it removes those extra bytes and repacks the ROM into the original zip file.
#
#


# Header to look for - script can be adapted to other simple ascii header tags like this one
$header_tag = "NES"
$header_length = 16


# Set script start time
$start_time = Get-Date

# Set counters
$total_files = (Get-ChildItem .\ -Filter *.zip | Measure-Object).Count
$cur_archive = 0
$parsed = 0
$fixed = 0

# Loop through all the zip files in the current folder
Get-ChildItem .\ -Filter *.zip | Foreach-Object {
	# Unpack zip file contents
	$zip = $_.FullName
	$rom_folder = "$($_.DirectoryName)\$($_.BaseName)"
	$global:ProgressPreference = "SilentlyContinue"
	Expand-Archive -LiteralPath $zip -Force

	# Show progress
	$cur_archive++
	$global:ProgressPreference = "Continue"
	$percentage = [math]::Round($cur_archive / $total_files * 100, 2)
	Write-Progress -Activity "Parsing ROM files" -Status "$percentage% Complete: $cur_archive/$total_files" -PercentComplete $percentage

	# Loop through the nes files in the rom folders
	Get-ChildItem -LiteralPath $rom_folder -Filter *.nes | Foreach-Object {
		# Read the rom file contents
		#"Parsing '$($_.Name)'..."
		$rom = $_.FullName
		$bytes = [System.IO.File]::ReadAllBytes($rom)

		# Get the rom file header
		$header = $null
		for ($i=0; $i -lt $header_tag.Length; $i++) {
			$header += [Convert]::ToString($bytes[$i], 16)
		}
		$ascii_header = -join ($header -split '(..)' | ? { $_ } | % { [char][convert]::ToUInt32($_,16) })

		# Check if the header matches what is expected
		if ($ascii_header -eq $header_tag) {
			# Output the rom file without the header
			[System.IO.File]::WriteAllBytes($rom, $bytes[$header_length..($bytes.count-1)])
			
			# Replace square brackets in the name (workaround due to M$ stupidity)
			if ($zip.Contains("[")) { $zip = $zip.replace("[", "_lsb_"); $sb_workaround = 1 }
			if ($zip.Contains("]")) { $zip = $zip.replace("]", "_rsb_"); $sb_workaround = 1 }
			
			# Repack the rom into the zip file (overwrites existing)
			$global:ProgressPreference = "SilentlyContinue"
			Compress-Archive -LiteralPath $rom -DestinationPath $zip -Force

			# Restore square brackets to the name (rolling-back workaround)
			if ($sb_workaround -eq 1) {
				$nicezip = $zip
				if ($zip.Contains("_lsb_")) { $zip = $zip.replace("_lsb_", "[") }
				if ($zip.Contains("_rsb_")) { $zip = $zip.replace("_rsb_", "]") }
				Move-Item -LiteralPath $nicezip -Destination $zip -Force
				$sb_workaround = 0
			}

			#"  * Fixed '$($_.Name)'..."
			$fixed++
		}
		$parsed++
	}
	# Remove the unpacked rom
	Remove-Item -LiteralPath $rom_folder -Recurse -Force -ErrorAction SilentlyContinue
}


# Output stats
"`n------------------------"
"   ZIP Files: $total_files"
" Parsed ROMs: $parsed"
"  Fixed ROMs: $fixed"
"------------------------"

# Get script end time
$end_time = Get-Date

# Calculate duration of execution
$diff = New-TimeSpan -Start $start_time -End $end_time
"Total duration: {0:hh\:mm\:ss}" -f ([TimeSpan] $diff)
"------------------------`n"

pause