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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// The file define a quoted-printable decoder, as specified in RFC 2045.
// Deviations:
// 1. in addition to "=\r\n", "=\n" is also treated as soft line break.
// 2. it will pass through a '\r' or '\n' not preceded by '=', consistent
// with other broken QP encoders & decoders.
package multipart
import (
"bufio"
"bytes"
"fmt"
"io"
)
type qpReader struct {
br *bufio.Reader
rerr error // last read error
line []byte // to be consumed before more of br
}
func newQuotedPrintableReader(r io.Reader) io.Reader {
return &qpReader{
br: bufio.NewReader(r),
}
}
func fromHex(b byte) (byte, error) {
switch {
case b >= '0' && b <= '9':
return b - '0', nil
case b >= 'A' && b <= 'F':
return b - 'A' + 10, nil
}
return 0, fmt.Errorf("multipart: invalid quoted-printable hex byte 0x%02x", b)
}
func (q *qpReader) readHexByte(v []byte) (b byte, err error) {
if len(v) < 2 {
return 0, io.ErrUnexpectedEOF
}
var hb, lb byte
if hb, err = fromHex(v[0]); err != nil {
return 0, err
}
if lb, err = fromHex(v[1]); err != nil {
return 0, err
}
return hb<<4 | lb, nil
}
func isQPDiscardWhitespace(r rune) bool {
switch r {
case '\n', '\r', ' ', '\t':
return true
}
return false
}
var (
crlf = []byte("\r\n")
lf = []byte("\n")
softSuffix = []byte("=")
)
func (q *qpReader) Read(p []byte) (n int, err error) {
for len(p) > 0 {
if len(q.line) == 0 {
if q.rerr != nil {
return n, q.rerr
}
q.line, q.rerr = q.br.ReadSlice('\n')
// Does the line end in CRLF instead of just LF?
hasLF := bytes.HasSuffix(q.line, lf)
hasCR := bytes.HasSuffix(q.line, crlf)
wholeLine := q.line
q.line = bytes.TrimRightFunc(wholeLine, isQPDiscardWhitespace)
if bytes.HasSuffix(q.line, softSuffix) {
rightStripped := wholeLine[len(q.line):]
q.line = q.line[:len(q.line)-1]
if !bytes.HasPrefix(rightStripped, lf) && !bytes.HasPrefix(rightStripped, crlf) {
q.rerr = fmt.Errorf("multipart: invalid bytes after =: %q", rightStripped)
}
} else if hasLF {
if hasCR {
q.line = append(q.line, '\r', '\n')
} else {
q.line = append(q.line, '\n')
}
}
continue
}
b := q.line[0]
switch {
case b == '=':
b, err = q.readHexByte(q.line[1:])
if err != nil {
return n, err
}
q.line = q.line[2:] // 2 of the 3; other 1 is done below
case b == '\t' || b == '\r' || b == '\n':
break
case b < ' ' || b > '~':
return n, fmt.Errorf("multipart: invalid unescaped byte 0x%02x in quoted-printable body", b)
}
p[0] = b
p = p[1:]
q.line = q.line[1:]
n++
}
return n, nil
}
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