diff --git a/server/websocket/internal/logic/datatransferlogic.go b/server/websocket/internal/logic/datatransferlogic.go
index 78f4d2dd..b712535f 100644
--- a/server/websocket/internal/logic/datatransferlogic.go
+++ b/server/websocket/internal/logic/datatransferlogic.go
@@ -185,11 +185,6 @@ func (l *DataTransferLogic) setConnPool(conn *websocket.Conn, userInfo *auth.Use
 	}
 	if oldWid != "" {
 		for i := 0; i < 1; i++ {
-			oldWid, err = encryption_decryption.NumberStrToBase64Str(oldWid)
-			if err != nil {
-				logx.Error("wid转base64失败:", err)
-				break
-			}
 			//解析传入的wid是不是属于自己的用户的
 			decryptionWid, err := encryption_decryption.CBCDecrypt(oldWid)
 			if err != nil {
@@ -278,7 +273,7 @@ func (l *DataTransferLogic) getUniqueId(userInfo *auth.UserInfo, userAgent strin
 	if err != nil {
 		return "", err
 	}
-	return encryption_decryption.Base64StrToNumberStr(uniqueId), nil
+	return uniqueId, nil
 }
 
 // 鉴权
diff --git a/utils/encryption_decryption/aes_cbc.go b/utils/encryption_decryption/aes_cbc.go
index cc823002..e03e4009 100644
--- a/utils/encryption_decryption/aes_cbc.go
+++ b/utils/encryption_decryption/aes_cbc.go
@@ -5,35 +5,13 @@ import (
 	"crypto/aes"
 	"crypto/cipher"
 	"crypto/rand"
-	"encoding/base64"
 	"fmt"
-	"strconv"
-	"strings"
+	"fusenapi/utils/selfdefine_base64"
 )
 
 // 必须16字节
 var cbckey = "fusen20230405145"
 
-func Base64StrToNumberStr(base64Str string) string {
-	s := strings.Builder{}
-	for _, v := range base64Str {
-		s.WriteString(fmt.Sprintf("%d.", v))
-	}
-	return strings.TrimRight(s.String(), ".")
-}
-func NumberStrToBase64Str(numberStr string) (string, error) {
-	s := strings.Split(numberStr, ".")
-	b := make([]int32, 0, len(s))
-	for _, v := range s {
-		c, err := strconv.Atoi(v)
-		if err != nil {
-			return "", err
-		}
-		b = append(b, int32(c))
-	}
-	return string(b), nil
-}
-
 // 加密(key必须16字节),前端加解密需要先把base64转字符串再取前16字节作为iv
 func CBCEncrypt(data string) (string, error) {
 	defer func() {
@@ -59,7 +37,7 @@ func CBCEncrypt(data string) (string, error) {
 	}
 	mode := cipher.NewCBCEncrypter(block, iv)
 	mode.CryptBlocks(ciphertext[aes.BlockSize:], []byte(data))
-	return base64.StdEncoding.EncodeToString(ciphertext), nil
+	return selfdefine_base64.StdEncoding.EncodeToString(ciphertext), nil
 }
 
 // 解密(key必须16字节)
@@ -73,7 +51,7 @@ func CBCDecrypt(src string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	ciphercode, err := base64.StdEncoding.DecodeString(src)
+	ciphercode, err := selfdefine_base64.StdEncoding.DecodeString(src)
 	if err != nil {
 		return "", err
 	}
diff --git a/utils/selfdefine_base64/base.go b/utils/selfdefine_base64/base.go
new file mode 100644
index 00000000..154fc164
--- /dev/null
+++ b/utils/selfdefine_base64/base.go
@@ -0,0 +1,622 @@
+package selfdefine_base64
+
+import (
+	"encoding/binary"
+	"io"
+	"strconv"
+)
+
+/*
+ * Encodings
+ */
+
+// An Encoding is a radix 64 encoding/decoding scheme, defined by a
+// 64-character alphabet. The most common encoding is the "base64"
+// encoding defined in RFC 4648 and used in MIME (RFC 2045) and PEM
+// (RFC 1421).  RFC 4648 also defines an alternate encoding, which is
+// the standard encoding with - and _ substituted for + and /.
+type Encoding struct {
+	encode    [64]byte
+	decodeMap [256]byte
+	padChar   rune
+	strict    bool
+}
+
+const (
+	StdPadding          rune = '=' // Standard padding character
+	NoPadding           rune = -1  // No padding
+	decodeMapInitialize      = "" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
+		"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
+)
+
+const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789#@"
+const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
+
+// NewEncoding returns a new padded Encoding defined by the given alphabet,
+// which must be a 64-byte string that does not contain the padding character
+// or CR / LF ('\r', '\n').
+// The resulting Encoding uses the default padding character ('='),
+// which may be changed or disabled via WithPadding.
+func NewEncoding(encoder string) *Encoding {
+	if len(encoder) != 64 {
+		panic("encoding alphabet is not 64-bytes long")
+	}
+	for i := 0; i < len(encoder); i++ {
+		if encoder[i] == '\n' || encoder[i] == '\r' {
+			panic("encoding alphabet contains newline character")
+		}
+	}
+
+	e := new(Encoding)
+	e.padChar = StdPadding
+	copy(e.encode[:], encoder)
+	copy(e.decodeMap[:], decodeMapInitialize)
+
+	for i := 0; i < len(encoder); i++ {
+		e.decodeMap[encoder[i]] = byte(i)
+	}
+	return e
+}
+
+// WithPadding creates a new encoding identical to enc except
+// with a specified padding character, or NoPadding to disable padding.
+// The padding character must not be '\r' or '\n', must not
+// be contained in the encoding's alphabet and must be a rune equal or
+// below '\xff'.
+func (enc Encoding) WithPadding(padding rune) *Encoding {
+	if padding == '\r' || padding == '\n' || padding > 0xff {
+		panic("invalid padding")
+	}
+
+	for i := 0; i < len(enc.encode); i++ {
+		if rune(enc.encode[i]) == padding {
+			panic("padding contained in alphabet")
+		}
+	}
+
+	enc.padChar = padding
+	return &enc
+}
+
+// Strict creates a new encoding identical to enc except with
+// strict decoding enabled. In this mode, the decoder requires that
+// trailing padding bits are zero, as described in RFC 4648 section 3.5.
+//
+// Note that the input is still malleable, as new line characters
+// (CR and LF) are still ignored.
+func (enc Encoding) Strict() *Encoding {
+	enc.strict = true
+	return &enc
+}
+
+// StdEncoding is the standard base64 encoding, as defined in
+// RFC 4648.
+var StdEncoding = NewEncoding(encodeStd)
+
+// URLEncoding is the alternate base64 encoding defined in RFC 4648.
+// It is typically used in URLs and file names.
+var URLEncoding = NewEncoding(encodeURL)
+
+// RawStdEncoding is the standard raw, unpadded base64 encoding,
+// as defined in RFC 4648 section 3.2.
+// This is the same as StdEncoding but omits padding characters.
+var RawStdEncoding = StdEncoding.WithPadding(NoPadding)
+
+// RawURLEncoding is the unpadded alternate base64 encoding defined in RFC 4648.
+// It is typically used in URLs and file names.
+// This is the same as URLEncoding but omits padding characters.
+var RawURLEncoding = URLEncoding.WithPadding(NoPadding)
+
+/*
+ * Encoder
+ */
+
+// Encode encodes src using the encoding enc, writing
+// EncodedLen(len(src)) bytes to dst.
+//
+// The encoding pads the output to a multiple of 4 bytes,
+// so Encode is not appropriate for use on individual blocks
+// of a large data stream. Use NewEncoder() instead.
+func (enc *Encoding) Encode(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+	// enc is a pointer receiver, so the use of enc.encode within the hot
+	// loop below means a nil check at every operation. Lift that nil check
+	// outside of the loop to speed up the encoder.
+	_ = enc.encode
+
+	di, si := 0, 0
+	n := (len(src) / 3) * 3
+	for si < n {
+		// Convert 3x 8bit source bytes into 4 bytes
+		val := uint(src[si+0])<<16 | uint(src[si+1])<<8 | uint(src[si+2])
+
+		dst[di+0] = enc.encode[val>>18&0x3F]
+		dst[di+1] = enc.encode[val>>12&0x3F]
+		dst[di+2] = enc.encode[val>>6&0x3F]
+		dst[di+3] = enc.encode[val&0x3F]
+
+		si += 3
+		di += 4
+	}
+
+	remain := len(src) - si
+	if remain == 0 {
+		return
+	}
+	// Add the remaining small block
+	val := uint(src[si+0]) << 16
+	if remain == 2 {
+		val |= uint(src[si+1]) << 8
+	}
+
+	dst[di+0] = enc.encode[val>>18&0x3F]
+	dst[di+1] = enc.encode[val>>12&0x3F]
+
+	switch remain {
+	case 2:
+		dst[di+2] = enc.encode[val>>6&0x3F]
+		if enc.padChar != NoPadding {
+			dst[di+3] = byte(enc.padChar)
+		}
+	case 1:
+		if enc.padChar != NoPadding {
+			dst[di+2] = byte(enc.padChar)
+			dst[di+3] = byte(enc.padChar)
+		}
+	}
+}
+
+// EncodeToString returns the base64 encoding of src.
+func (enc *Encoding) EncodeToString(src []byte) string {
+	buf := make([]byte, enc.EncodedLen(len(src)))
+	enc.Encode(buf, src)
+	return string(buf)
+}
+
+type encoder struct {
+	err  error
+	enc  *Encoding
+	w    io.Writer
+	buf  [3]byte    // buffered data waiting to be encoded
+	nbuf int        // number of bytes in buf
+	out  [1024]byte // output buffer
+}
+
+func (e *encoder) Write(p []byte) (n int, err error) {
+	if e.err != nil {
+		return 0, e.err
+	}
+
+	// Leading fringe.
+	if e.nbuf > 0 {
+		var i int
+		for i = 0; i < len(p) && e.nbuf < 3; i++ {
+			e.buf[e.nbuf] = p[i]
+			e.nbuf++
+		}
+		n += i
+		p = p[i:]
+		if e.nbuf < 3 {
+			return
+		}
+		e.enc.Encode(e.out[:], e.buf[:])
+		if _, e.err = e.w.Write(e.out[:4]); e.err != nil {
+			return n, e.err
+		}
+		e.nbuf = 0
+	}
+
+	// Large interior chunks.
+	for len(p) >= 3 {
+		nn := len(e.out) / 4 * 3
+		if nn > len(p) {
+			nn = len(p)
+			nn -= nn % 3
+		}
+		e.enc.Encode(e.out[:], p[:nn])
+		if _, e.err = e.w.Write(e.out[0 : nn/3*4]); e.err != nil {
+			return n, e.err
+		}
+		n += nn
+		p = p[nn:]
+	}
+
+	// Trailing fringe.
+	copy(e.buf[:], p)
+	e.nbuf = len(p)
+	n += len(p)
+	return
+}
+
+// Close flushes any pending output from the encoder.
+// It is an error to call Write after calling Close.
+func (e *encoder) Close() error {
+	// If there's anything left in the buffer, flush it out
+	if e.err == nil && e.nbuf > 0 {
+		e.enc.Encode(e.out[:], e.buf[:e.nbuf])
+		_, e.err = e.w.Write(e.out[:e.enc.EncodedLen(e.nbuf)])
+		e.nbuf = 0
+	}
+	return e.err
+}
+
+// NewEncoder returns a new base64 stream encoder. Data written to
+// the returned writer will be encoded using enc and then written to w.
+// Base64 encodings operate in 4-byte blocks; when finished
+// writing, the caller must Close the returned encoder to flush any
+// partially written blocks.
+func NewEncoder(enc *Encoding, w io.Writer) io.WriteCloser {
+	return &encoder{enc: enc, w: w}
+}
+
+// EncodedLen returns the length in bytes of the base64 encoding
+// of an input buffer of length n.
+func (enc *Encoding) EncodedLen(n int) int {
+	if enc.padChar == NoPadding {
+		return (n*8 + 5) / 6 // minimum # chars at 6 bits per char
+	}
+	return (n + 2) / 3 * 4 // minimum # 4-char quanta, 3 bytes each
+}
+
+/*
+ * Decoder
+ */
+
+type CorruptInputError int64
+
+func (e CorruptInputError) Error() string {
+	return "illegal base64 data at input byte " + strconv.FormatInt(int64(e), 10)
+}
+
+// decodeQuantum decodes up to 4 base64 bytes. The received parameters are
+// the destination buffer dst, the source buffer src and an index in the
+// source buffer si.
+// It returns the number of bytes read from src, the number of bytes written
+// to dst, and an error, if any.
+func (enc *Encoding) decodeQuantum(dst, src []byte, si int) (nsi, n int, err error) {
+	// Decode quantum using the base64 alphabet
+	var dbuf [4]byte
+	dlen := 4
+
+	// Lift the nil check outside of the loop.
+	_ = enc.decodeMap
+
+	for j := 0; j < len(dbuf); j++ {
+		if len(src) == si {
+			switch {
+			case j == 0:
+				return si, 0, nil
+			case j == 1, enc.padChar != NoPadding:
+				return si, 0, CorruptInputError(si - j)
+			}
+			dlen = j
+			break
+		}
+		in := src[si]
+		si++
+
+		out := enc.decodeMap[in]
+		if out != 0xff {
+			dbuf[j] = out
+			continue
+		}
+
+		if in == '\n' || in == '\r' {
+			j--
+			continue
+		}
+
+		if rune(in) != enc.padChar {
+			return si, 0, CorruptInputError(si - 1)
+		}
+
+		// We've reached the end and there's padding
+		switch j {
+		case 0, 1:
+			// incorrect padding
+			return si, 0, CorruptInputError(si - 1)
+		case 2:
+			// "==" is expected, the first "=" is already consumed.
+			// skip over newlines
+			for si < len(src) && (src[si] == '\n' || src[si] == '\r') {
+				si++
+			}
+			if si == len(src) {
+				// not enough padding
+				return si, 0, CorruptInputError(len(src))
+			}
+			if rune(src[si]) != enc.padChar {
+				// incorrect padding
+				return si, 0, CorruptInputError(si - 1)
+			}
+
+			si++
+		}
+
+		// skip over newlines
+		for si < len(src) && (src[si] == '\n' || src[si] == '\r') {
+			si++
+		}
+		if si < len(src) {
+			// trailing garbage
+			err = CorruptInputError(si)
+		}
+		dlen = j
+		break
+	}
+
+	// Convert 4x 6bit source bytes into 3 bytes
+	val := uint(dbuf[0])<<18 | uint(dbuf[1])<<12 | uint(dbuf[2])<<6 | uint(dbuf[3])
+	dbuf[2], dbuf[1], dbuf[0] = byte(val>>0), byte(val>>8), byte(val>>16)
+	switch dlen {
+	case 4:
+		dst[2] = dbuf[2]
+		dbuf[2] = 0
+		fallthrough
+	case 3:
+		dst[1] = dbuf[1]
+		if enc.strict && dbuf[2] != 0 {
+			return si, 0, CorruptInputError(si - 1)
+		}
+		dbuf[1] = 0
+		fallthrough
+	case 2:
+		dst[0] = dbuf[0]
+		if enc.strict && (dbuf[1] != 0 || dbuf[2] != 0) {
+			return si, 0, CorruptInputError(si - 2)
+		}
+	}
+
+	return si, dlen - 1, err
+}
+
+// DecodeString returns the bytes represented by the base64 string s.
+func (enc *Encoding) DecodeString(s string) ([]byte, error) {
+	dbuf := make([]byte, enc.DecodedLen(len(s)))
+	n, err := enc.Decode(dbuf, []byte(s))
+	return dbuf[:n], err
+}
+
+type decoder struct {
+	err     error
+	readErr error // error from r.Read
+	enc     *Encoding
+	r       io.Reader
+	buf     [1024]byte // leftover input
+	nbuf    int
+	out     []byte // leftover decoded output
+	outbuf  [1024 / 4 * 3]byte
+}
+
+func (d *decoder) Read(p []byte) (n int, err error) {
+	// Use leftover decoded output from last read.
+	if len(d.out) > 0 {
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+		return n, nil
+	}
+
+	if d.err != nil {
+		return 0, d.err
+	}
+
+	// This code assumes that d.r strips supported whitespace ('\r' and '\n').
+
+	// Refill buffer.
+	for d.nbuf < 4 && d.readErr == nil {
+		nn := len(p) / 3 * 4
+		if nn < 4 {
+			nn = 4
+		}
+		if nn > len(d.buf) {
+			nn = len(d.buf)
+		}
+		nn, d.readErr = d.r.Read(d.buf[d.nbuf:nn])
+		d.nbuf += nn
+	}
+
+	if d.nbuf < 4 {
+		if d.enc.padChar == NoPadding && d.nbuf > 0 {
+			// Decode final fragment, without padding.
+			var nw int
+			nw, d.err = d.enc.Decode(d.outbuf[:], d.buf[:d.nbuf])
+			d.nbuf = 0
+			d.out = d.outbuf[:nw]
+			n = copy(p, d.out)
+			d.out = d.out[n:]
+			if n > 0 || len(p) == 0 && len(d.out) > 0 {
+				return n, nil
+			}
+			if d.err != nil {
+				return 0, d.err
+			}
+		}
+		d.err = d.readErr
+		if d.err == io.EOF && d.nbuf > 0 {
+			d.err = io.ErrUnexpectedEOF
+		}
+		return 0, d.err
+	}
+
+	// Decode chunk into p, or d.out and then p if p is too small.
+	nr := d.nbuf / 4 * 4
+	nw := d.nbuf / 4 * 3
+	if nw > len(p) {
+		nw, d.err = d.enc.Decode(d.outbuf[:], d.buf[:nr])
+		d.out = d.outbuf[:nw]
+		n = copy(p, d.out)
+		d.out = d.out[n:]
+	} else {
+		n, d.err = d.enc.Decode(p, d.buf[:nr])
+	}
+	d.nbuf -= nr
+	copy(d.buf[:d.nbuf], d.buf[nr:])
+	return n, d.err
+}
+
+// Decode decodes src using the encoding enc. It writes at most
+// DecodedLen(len(src)) bytes to dst and returns the number of bytes
+// written. If src contains invalid base64 data, it will return the
+// number of bytes successfully written and CorruptInputError.
+// New line characters (\r and \n) are ignored.
+func (enc *Encoding) Decode(dst, src []byte) (n int, err error) {
+	if len(src) == 0 {
+		return 0, nil
+	}
+
+	// Lift the nil check outside of the loop. enc.decodeMap is directly
+	// used later in this function, to let the compiler know that the
+	// receiver can't be nil.
+	_ = enc.decodeMap
+
+	si := 0
+	for strconv.IntSize >= 64 && len(src)-si >= 8 && len(dst)-n >= 8 {
+		src2 := src[si : si+8]
+		if dn, ok := assemble64(
+			enc.decodeMap[src2[0]],
+			enc.decodeMap[src2[1]],
+			enc.decodeMap[src2[2]],
+			enc.decodeMap[src2[3]],
+			enc.decodeMap[src2[4]],
+			enc.decodeMap[src2[5]],
+			enc.decodeMap[src2[6]],
+			enc.decodeMap[src2[7]],
+		); ok {
+			binary.BigEndian.PutUint64(dst[n:], dn)
+			n += 6
+			si += 8
+		} else {
+			var ninc int
+			si, ninc, err = enc.decodeQuantum(dst[n:], src, si)
+			n += ninc
+			if err != nil {
+				return n, err
+			}
+		}
+	}
+
+	for len(src)-si >= 4 && len(dst)-n >= 4 {
+		src2 := src[si : si+4]
+		if dn, ok := assemble32(
+			enc.decodeMap[src2[0]],
+			enc.decodeMap[src2[1]],
+			enc.decodeMap[src2[2]],
+			enc.decodeMap[src2[3]],
+		); ok {
+			binary.BigEndian.PutUint32(dst[n:], dn)
+			n += 3
+			si += 4
+		} else {
+			var ninc int
+			si, ninc, err = enc.decodeQuantum(dst[n:], src, si)
+			n += ninc
+			if err != nil {
+				return n, err
+			}
+		}
+	}
+
+	for si < len(src) {
+		var ninc int
+		si, ninc, err = enc.decodeQuantum(dst[n:], src, si)
+		n += ninc
+		if err != nil {
+			return n, err
+		}
+	}
+	return n, err
+}
+
+// assemble32 assembles 4 base64 digits into 3 bytes.
+// Each digit comes from the decode map, and will be 0xff
+// if it came from an invalid character.
+func assemble32(n1, n2, n3, n4 byte) (dn uint32, ok bool) {
+	// Check that all the digits are valid. If any of them was 0xff, their
+	// bitwise OR will be 0xff.
+	if n1|n2|n3|n4 == 0xff {
+		return 0, false
+	}
+	return uint32(n1)<<26 |
+			uint32(n2)<<20 |
+			uint32(n3)<<14 |
+			uint32(n4)<<8,
+		true
+}
+
+// assemble64 assembles 8 base64 digits into 6 bytes.
+// Each digit comes from the decode map, and will be 0xff
+// if it came from an invalid character.
+func assemble64(n1, n2, n3, n4, n5, n6, n7, n8 byte) (dn uint64, ok bool) {
+	// Check that all the digits are valid. If any of them was 0xff, their
+	// bitwise OR will be 0xff.
+	if n1|n2|n3|n4|n5|n6|n7|n8 == 0xff {
+		return 0, false
+	}
+	return uint64(n1)<<58 |
+			uint64(n2)<<52 |
+			uint64(n3)<<46 |
+			uint64(n4)<<40 |
+			uint64(n5)<<34 |
+			uint64(n6)<<28 |
+			uint64(n7)<<22 |
+			uint64(n8)<<16,
+		true
+}
+
+type newlineFilteringReader struct {
+	wrapped io.Reader
+}
+
+func (r *newlineFilteringReader) Read(p []byte) (int, error) {
+	n, err := r.wrapped.Read(p)
+	for n > 0 {
+		offset := 0
+		for i, b := range p[:n] {
+			if b != '\r' && b != '\n' {
+				if i != offset {
+					p[offset] = b
+				}
+				offset++
+			}
+		}
+		if offset > 0 {
+			return offset, err
+		}
+		// Previous buffer entirely whitespace, read again
+		n, err = r.wrapped.Read(p)
+	}
+	return n, err
+}
+
+// NewDecoder constructs a new base64 stream decoder.
+func NewDecoder(enc *Encoding, r io.Reader) io.Reader {
+	return &decoder{enc: enc, r: &newlineFilteringReader{r}}
+}
+
+// DecodedLen returns the maximum length in bytes of the decoded data
+// corresponding to n bytes of base64-encoded data.
+func (enc *Encoding) DecodedLen(n int) int {
+	if enc.padChar == NoPadding {
+		// Unpadded data may end with partial block of 2-3 characters.
+		return n * 6 / 8
+	}
+	// Padded base64 should always be a multiple of 4 characters in length.
+	return n / 4 * 3
+}