mime/quotedprintable: Return a Reader instead of an io.Reader

It is not needed right now, but it will allow more flexibility in
the future.

Fixes #10472

Change-Id: I2eaea70abeca5ed10f89b0b2dfdabdac376a0a41
Reviewed-on: https://go-review.googlesource.com/8964
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/mime/quotedprintable/reader.go b/src/mime/quotedprintable/reader.go
index a39a20ef8358b546879f9c06d928773bbe0c061f..3bd6833da5fb8f52febec95e49145675b80d23a2 100644 (file)
--- a/src/mime/quotedprintable/reader.go
+++ b/src/mime/quotedprintable/reader.go
@@ -13,19 +13,16 @@ import (
        "io"
 )
 
-// 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.
-type reader struct {
+// 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) io.Reader {
-       return &reader{
+func NewReader(r io.Reader) *Reader {
+       return &Reader{
                br: bufio.NewReader(r),
        }
 }
@@ -43,7 +40,7 @@ func fromHex(b byte) (byte, error) {
        return 0, fmt.Errorf("quotedprintable: invalid hex byte 0x%02x", b)
 }
 
-func (q *reader) readHexByte(v []byte) (b byte, err error) {
+func readHexByte(v []byte) (b byte, err error) {
        if len(v) < 2 {
                return 0, io.ErrUnexpectedEOF
        }
@@ -71,43 +68,48 @@ var (
        softSuffix = []byte("=")
 )
 
-func (q *reader) Read(p []byte) (n int, err error) {
+// 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(q.line) == 0 {
-                       if q.rerr != nil {
-                               return n, q.rerr
+               if len(r.line) == 0 {
+                       if r.rerr != nil {
+                               return n, r.rerr
                        }
-                       q.line, q.rerr = q.br.ReadSlice('\n')
+                       r.line, r.rerr = r.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]
+                       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) {
-                                       q.rerr = fmt.Errorf("quotedprintable: invalid bytes after =: %q", rightStripped)
+                                       r.rerr = fmt.Errorf("quotedprintable: invalid bytes after =: %q", rightStripped)
                                }
                        } else if hasLF {
                                if hasCR {
-                                       q.line = append(q.line, '\r', '\n')
+                                       r.line = append(r.line, '\r', '\n')
                                } else {
-                                       q.line = append(q.line, '\n')
+                                       r.line = append(r.line, '\n')
                                }
                        }
                        continue
                }
-               b := q.line[0]
+               b := r.line[0]
 
                switch {
                case b == '=':
-                       b, err = q.readHexByte(q.line[1:])
+                       b, err = readHexByte(r.line[1:])
                        if err != nil {
                                return n, err
                        }
-                       q.line = q.line[2:] // 2 of the 3; other 1 is done below
+                       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 > '~':
@@ -115,7 +117,7 @@ func (q *reader) Read(p []byte) (n int, err error) {
                }
                p[0] = b
                p = p[1:]
-               q.line = q.line[1:]
+               r.line = r.line[1:]
                n++
        }
        return n, nil