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