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// Package quotedprintable implements quoted-printable encoding as specified by
// RFC 2045.
package quotedprintable
import (
"bufio"
"bytes"
"fmt"
"io"
)
// Reader is a quoted-printable decoder.
type Reader struct {
br *bufio.Reader
rerr error // last read error
line []byte // to be consumed before more of br
}
// NewReader returns a quoted-printable reader, decoding from r.
func NewReader(r io.Reader) *Reader {
return &Reader{
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
// Accept badly encoded bytes.
case b >= 'a' && b <= 'f':
return b - 'a' + 10, nil
}
return 0, fmt.Errorf("quotedprintable: invalid hex byte 0x%02x", b)
}
func readHexByte(a, b byte) (byte, error) {
var hb, lb byte
var err error
if hb, err = fromHex(a); err != nil {
return 0, err
}
if lb, err = fromHex(b); 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("=")
)
// Read reads and decodes quoted-printable data from the underlying reader.
func (r *Reader) Read(p []byte) (n int, err error) {
// Deviations from RFC 2045:
// 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.
for len(p) > 0 {
if len(r.line) == 0 {
if r.rerr != nil {
return n, r.rerr
}
r.line, r.rerr = r.br.ReadSlice('\n')
// Does the line end in CRLF instead of just LF?
hasLF := bytes.HasSuffix(r.line, lf)
hasCR := bytes.HasSuffix(r.line, crlf)
wholeLine := r.line
r.line = bytes.TrimRightFunc(wholeLine, isQPDiscardWhitespace)
if bytes.HasSuffix(r.line, softSuffix) {
rightStripped := wholeLine[len(r.line):]
r.line = r.line[:len(r.line)-1]
if !bytes.HasPrefix(rightStripped, lf) && !bytes.HasPrefix(rightStripped, crlf) {
r.rerr = fmt.Errorf("quotedprintable: invalid bytes after =: %q", rightStripped)
}
} else if hasLF {
if hasCR {
r.line = append(r.line, '\r', '\n')
} else {
r.line = append(r.line, '\n')
}
}
continue
}
b := r.line[0]
switch {
case b == '=':
if len(r.line[1:]) < 2 {
return n, io.ErrUnexpectedEOF
}
b, err = readHexByte(r.line[1], r.line[2])
if err != nil {
return n, err
}
r.line = r.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("quotedprintable: invalid unescaped byte 0x%02x in body", b)
}
p[0] = b
p = p[1:]
r.line = r.line[1:]
n++
}
return n, nil
}
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