BP_GOPP_Image_Editor_GS::gs_valid( string $file, bool $no_read_check = false )

	protected static function gs_valid( $file, $no_read_check = false ) {
		// Loading from URL not currently supported.
		if ( preg_match( '|^https?://|', $file ) ) {
			return __( 'Loading from URL not supported.', 'buddyboss' );
		}

		// Check filename can't be interpreted by Ghostscript as special - see https://ghostscript.com/doc/9.20/Use.htm#Options
		if ( preg_match( '/^[@|%-]/', $file ) ) {
			return __( 'Unsupported file name.', 'buddyboss' );
		}

		// Check for suspect chars in base filename - same as $special_chars in sanitize_file_name() with ctrls, space and del added
		// but (for BC with common older uploads) with "+" removed - see #16226 for its addition (along with "%") Oct 2015.
		if ( preg_match( '/[?\[\]\/\\\\=<>:;,\'"&$#*()|~`!{}%\x00-\x20\x7f]/', wp_basename( $file ) ) ) {
			return __( 'Unsupported file name.', 'buddyboss' );
		}

		if ( $no_read_check ) {
			return true;
		}

		// Check existence & magic bytes.
		$fp = @ fopen( $file, 'rb' );
		if ( false === $fp ) {
			return __( 'File doesn&#8217;t exist?', 'buddyboss' );
		}
		$magic_bytes = fread( $fp, 10 ); // Max 10 chars: "%PDF-N.NN" plus optional initial linefeed.
		fclose( $fp );
		// This is a similar test to that done by libmagic, but more strict on version format by insisting it's "0." or "1." followed by 1 or 2 numbers.
		if ( ! preg_match( '/^\n?%PDF-[01]\.[0-9]{1,2}/', $magic_bytes ) ) {
			do_action( 'gopp_error', __CLASS__, __FUNCTION__, __LINE__, compact( 'file', 'magic_bytes' ) );
			return __( 'File is not a PDF.', 'buddyboss' );
		}

		return true;
	}