words" => "8O\x00:)\x00:(\x00:?\x00",
	 *             "small_mappings" => array( "😯", "🙂", "🙁", "😕" )
	 *         )
	 *     );
	 *
	 * @since 6.6.0
	 *
	 * @param string $indent Optional. Use this string for indentation, or rely on the default horizontal tab character. Default "\t".
	 * @return string Value which can be pasted into a PHP source file for quick loading of table.
	 */
	public function precomputed_php_source_table( string $indent = "\t" ): string {
		$i1 = $indent;
		$i2 = $i1 . $indent;
		$i3 = $i2 . $indent;

		$class_version = self::STORAGE_VERSION;

		$output  = self::class . "::from_precomputed_table(\n";
		$output .= "{$i1}array(\n";
		$output .= "{$i2}\"storage_version\" => \"{$class_version}\",\n";
		$output .= "{$i2}\"key_length\" => {$this->key_length},\n";

		$group_line = str_replace( "\x00", "\\x00", $this->groups );
		$output    .= "{$i2}\"groups\" => \"{$group_line}\",\n";

		$output .= "{$i2}\"large_words\" => array(\n";

		$prefixes = explode( "\x00", $this->groups );
		foreach ( $prefixes as $index => $prefix ) {
			if ( '' === $prefix ) {
				break;
			}
			$group        = $this->large_words[ $index ];
			$group_length = strlen( $group );
			$comment_line = "{$i3}//";
			$data_line    = "{$i3}\"";
			$at           = 0;
			while ( $at < $group_length ) {
				$token_length   = unpack( 'C', $group[ $at++ ] )[1];
				$token          = substr( $group, $at, $token_length );
				$at            += $token_length;
				$mapping_length = unpack( 'C', $group[ $at++ ] )[1];
				$mapping        = substr( $group, $at, $mapping_length );
				$at            += $mapping_length;

				$token_digits   = str_pad( dechex( $token_length ), 2, '0', STR_PAD_LEFT );
				$mapping_digits = str_pad( dechex( $mapping_length ), 2, '0', STR_PAD_LEFT );

				$mapping = preg_replace_callback(
					"~[\\x00-\\x1f\\x22\\x5c]~",
					static function ( $match_result ) {
						switch ( $match_result[0] ) {
							case '"':
								return '\\"';

							case '\\':
								return '\\\\';

							default:
								$hex = dechex( ord( $match_result[0] ) );
								return "\\x{$hex}";
						}
					},
					$mapping
				);

				$comment_line .= " {$prefix}{$token}[{$mapping}]";
				$data_line    .= "\\x{$token_digits}{$token}\\x{$mapping_digits}{$mapping}";
			}
			$comment_line .= ".\n";
			$data_line    .= "\",\n";

			$output .= $comment_line;
			$output .= $data_line;
		}

		$output .= "{$i2}),\n";

		$small_words  = array();
		$small_length = strlen( $this->small_words );
		$at           = 0;
		while ( $at < $small_length ) {
			$small_words[] = substr( $this->small_words, $at, $this->key_length + 1 );
			$at           += $this->key_length + 1;
		}

		$small_text = str_replace( "\x00", '\x00', implode( '', $small_words ) );
		$output    .= "{$i2}\"small_words\" => \"{$small_text}\",\n";

		$output .= "{$i2}\"small_mappings\" => array(\n";
		foreach ( $this->small_mappings as $mapping ) {
			$output .= "{$i3}\"{$mapping}\",\n";
		}
		$output .= "{$i2})\n";
		$output .= "{$i1})\n";
		$output .= ')';

		return $output;
	}

	/**
	 * Compares two strings, returning the longest, or whichever
	 * is first alphabetically if they are the same length.
	 *
	 * This is an important sort when building the token map because
	 * it should not form a match on a substring of a longer potential
	 * match. For example, it should not detect `Cap` when matching
	 * against the string `CapitalDifferentialD`.
	 *
	 * @since 6.6.0
	 *
	 * @param string $a First string to compare.
	 * @param string $b Second string to compare.
	 * @return int -1 or lower if `$a` is less than `$b`; 1 or greater if `$a` is greater than `$b`, and 0 if they are equal.
	 */
	private static function longest_first_then_alphabetical( string $a, string $b ): int {
		if ( $a === $b ) {
			return 0;
		}

		$length_a = strlen( $a );
		$length_b = strlen( $b );

		// Longer strings are less-than for comparison's sake.
		if ( $length_a !== $length_b ) {
			return $length_b - $length_a;
		}

		return strcmp( $a, $b );
	}
}
sion_from_header( $this->headers['plural-forms'] );
			$this->plural_forms = $this->make_plural_form_function( $expression );
		}

		if ( is_callable( $this->plural_forms ) ) {
			/**
			 * Plural form.
			 *
			 * @var int $result Plural form.
			 */
			$result = call_user_func( $this->plural_forms, $number );

			return $result;
		}

		// Default plural form matches English, only "One" is considered singular.
		return ( 1 === $number ? 0 : 1 );
	}

	/**
	 * Returns the plural forms expression as a tuple.
	 *
	 * @since 6.5.0
	 *
	 * @param string $header Plural-Forms header string.
	 * @return string Plural forms expression.
	 */
	protected function get_plural_expression_from_header( string $header ): string {
		if ( preg_match( '/^\s*nplurals\s*=\s*(\d+)\s*;\s+plural\s*=\s*(.+)$/', $header, $matches ) ) {
			return trim( $matches[2] );
		}

		return 'n != 1';
	}

	/**
	 * Makes a function, which will return the right translation index, according to the
	 * plural forms header.
	 *
	 * @since 6.5.0
	 *
	 * @param string $expression Plural form expression.
	 * @return callable(int $num): int Plural forms function.
	 */
	protected function make_plural_form_function( string $expression ): callable {
		try {
			$handler = new Plural_Forms( rtrim( $expression, ';' ) );
			return array( $handler, 'get' );
		} catch ( Exception $e ) {
			// Fall back to default plural-form function.
			return $this->make_plural_form_function( 'n != 1' );
		}
	}

	/**
	 * Imports translations from another file.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_Translation_File $source Source file.
	 * @return bool True on success, false otherwise.
	 */
	protected function import( WP_Translation_File $source ): bool {
		if ( null !== $source->error() ) {
			return false;
		}

		$this->headers = $source->headers();
		$this->entries = $source->entries();
		$this->error   = $source->error();

		return null === $this->error;
	}

	/**
	 * Parses the file.
	 *
	 * @since 6.5.0
	 */
	abstract protected function parse_file();

	/**
	 * Exports translation contents as a string.
	 *
	 * @since 6.5.0
	 *
	 * @return string Translation file contents.
	 */
	abstract public function export();
}