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121 lines
2.8 KiB
121 lines
2.8 KiB
// Package quotedprintable implements quoted-printable encoding as specified by
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// RFC 2045.
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package quotedprintable
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import (
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"bufio"
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"bytes"
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"fmt"
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"io"
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)
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// Reader is a quoted-printable decoder.
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type Reader struct {
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br *bufio.Reader
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rerr error // last read error
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line []byte // to be consumed before more of br
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}
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// NewReader returns a quoted-printable reader, decoding from r.
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func NewReader(r io.Reader) *Reader {
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return &Reader{
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br: bufio.NewReader(r),
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}
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}
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func fromHex(b byte) (byte, error) {
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switch {
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case b >= '0' && b <= '9':
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return b - '0', nil
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case b >= 'A' && b <= 'F':
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return b - 'A' + 10, nil
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// Accept badly encoded bytes.
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case b >= 'a' && b <= 'f':
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return b - 'a' + 10, nil
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}
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return 0, fmt.Errorf("quotedprintable: invalid hex byte 0x%02x", b)
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}
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func readHexByte(a, b byte) (byte, error) {
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var hb, lb byte
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var err error
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if hb, err = fromHex(a); err != nil {
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return 0, err
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}
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if lb, err = fromHex(b); err != nil {
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return 0, err
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}
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return hb<<4 | lb, nil
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}
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func isQPDiscardWhitespace(r rune) bool {
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switch r {
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case '\n', '\r', ' ', '\t':
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return true
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}
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return false
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}
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var (
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crlf = []byte("\r\n")
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lf = []byte("\n")
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softSuffix = []byte("=")
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)
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// Read reads and decodes quoted-printable data from the underlying reader.
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func (r *Reader) Read(p []byte) (n int, err error) {
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// Deviations from RFC 2045:
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// 1. in addition to "=\r\n", "=\n" is also treated as soft line break.
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// 2. it will pass through a '\r' or '\n' not preceded by '=', consistent
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// with other broken QP encoders & decoders.
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for len(p) > 0 {
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if len(r.line) == 0 {
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if r.rerr != nil {
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return n, r.rerr
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}
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r.line, r.rerr = r.br.ReadSlice('\n')
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// Does the line end in CRLF instead of just LF?
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hasLF := bytes.HasSuffix(r.line, lf)
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hasCR := bytes.HasSuffix(r.line, crlf)
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wholeLine := r.line
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r.line = bytes.TrimRightFunc(wholeLine, isQPDiscardWhitespace)
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if bytes.HasSuffix(r.line, softSuffix) {
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rightStripped := wholeLine[len(r.line):]
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r.line = r.line[:len(r.line)-1]
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if !bytes.HasPrefix(rightStripped, lf) && !bytes.HasPrefix(rightStripped, crlf) {
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r.rerr = fmt.Errorf("quotedprintable: invalid bytes after =: %q", rightStripped)
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}
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} else if hasLF {
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if hasCR {
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r.line = append(r.line, '\r', '\n')
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} else {
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r.line = append(r.line, '\n')
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}
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}
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continue
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}
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b := r.line[0]
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switch {
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case b == '=':
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if len(r.line[1:]) < 2 {
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return n, io.ErrUnexpectedEOF
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}
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b, err = readHexByte(r.line[1], r.line[2])
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if err != nil {
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return n, err
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}
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r.line = r.line[2:] // 2 of the 3; other 1 is done below
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case b == '\t' || b == '\r' || b == '\n':
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break
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case b < ' ' || b > '~':
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return n, fmt.Errorf("quotedprintable: invalid unescaped byte 0x%02x in body", b)
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}
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p[0] = b
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p = p[1:]
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r.line = r.line[1:]
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n++
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}
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return n, nil
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}
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