package filename import (	"bytes"	"encoding/base64"	"encoding/binary"	"errors"	"sync" 	"github.com/klauspost/compress/huff0") // ErrCorrupted is returned if a provided encoded filename cannot be decoded.var ErrCorrupted = errors.New("file name corrupt") // ErrUnsupported is returned if a provided encoding may come from a future version or the file name is corrupt.var ErrUnsupported = errors.New("file name possibly generated by future version of rclone") // Custom decoder for tableCustom types. Stateful, so must have lock.var customDec huff0.Scratchvar customDecMu sync.Mutex // Decode an encoded string.func Decode(s string) (string, error) {	initCoders()	if len(s) < 1 {		return "", ErrCorrupted	}	table := decodeMap[s[0]]	if table == 0 {		return "", ErrCorrupted	}	table--	s = s[1:]	data := make([]byte, base64.URLEncoding.DecodedLen(len(s)))	n, err := base64.URLEncoding.Decode(data, ([]byte)(s))	if err != nil || n < 0 {		return "", ErrCorrupted	}	data = data[:n]	return DecodeBytes(table, data)} // DecodeBytes will decode raw id and data values.func DecodeBytes(table byte, data []byte) (string, error) {	initCoders()	switch table {	case tableUncompressed:		return string(data), nil	case tableReserved:		return "", ErrUnsupported	case tableSCSUPlain:		return scsuDecode(data)	case tableRLE:		if len(data) < 2 {			return "", ErrCorrupted		}		n, used := binary.Uvarint(data[:len(data)-1])		if used <= 0 || n > maxLength {			return "", ErrCorrupted		}		return string(bytes.Repeat(data[len(data)-1:], int(n))), nil	case tableCustom:		customDecMu.Lock()		defer customDecMu.Unlock()		_, data, err := huff0.ReadTable(data, &customDec)		if err != nil {			return "", ErrCorrupted		}		customDec.MaxDecodedSize = maxLength		decoded, err := customDec.Decompress1X(data)		if err != nil {			return "", ErrCorrupted		}		return string(decoded), nil	default:		if table >= byte(len(decTables)) {			return "", ErrCorrupted		}		dec := decTables[table]		if dec == nil {			return "", ErrUnsupported		}		var dst [maxLength]byte		name, err := dec.Decompress1X(dst[:0], data)		if err != nil {			return "", ErrCorrupted		}		if table == tableSCSU {			return scsuDecode(name)		}		return string(name), nil	}}