emersion · emersion · Mar 3, 2024 · Mar 2, 2024
diff --git a/encoding.go b/encoding.go
@@ -1,14 +1,13 @@
 package message
 
 import (
+	"bytes"
 	"encoding/base64"
 	"errors"
 	"fmt"
 	"io"
 	"mime/quotedprintable"
 	"strings"
-
-	"github.com/emersion/go-textwrapper"
 )
 
 type UnknownEncodingError struct {
@@ -57,9 +56,9 @@ func encodingWriter(enc string, w io.Writer) (io.WriteCloser, error) {
 	case "quoted-printable":
 		wc = quotedprintable.NewWriter(w)
 	case "base64":
-		wc = base64.NewEncoder(base64.StdEncoding, textwrapper.NewRFC822(w))
+		wc = base64.NewEncoder(base64.StdEncoding, &lineWrapper{w: w, maxLineLen: 76})
 	case "7bit", "8bit":
-		wc = nopCloser{textwrapper.New(w, "\r\n", 1000)}
+		wc = nopCloser{&lineWrapper{w: w, maxLineLen: 998}}
 	case "binary", "":
 		wc = nopCloser{w}
 	default:
@@ -86,3 +85,67 @@ func (r *whitespaceReplacingReader) Read(p []byte) (int, error) {
 
 	return n, err
 }
+
+type lineWrapper struct {
+	w          io.Writer
+	maxLineLen int
+
+	curLineLen int
+	cr         bool
+}
+
+func (w *lineWrapper) Write(b []byte) (int, error) {
+	var written int
+	for len(b) > 0 {
+		var l []byte
+		l, b = cutLine(b, w.maxLineLen-w.curLineLen)
+
+		lf := bytes.HasSuffix(l, []byte("\n"))
+		l = bytes.TrimSuffix(l, []byte("\n"))
+
+		n, err := w.w.Write(l)
+		if err != nil {
+			return written, err
+		}
+		written += n
+
+		cr := bytes.HasSuffix(l, []byte("\r"))
+		if len(l) == 0 {
+			cr = w.cr
+		}
+
+		if !lf && len(b) == 0 {
+			w.curLineLen += len(l)
+			w.cr = cr
+			break
+		}
+		w.curLineLen = 0
+
+		ending := []byte("\r\n")
+		if cr {
+			ending = []byte("\n")
+		}
+		_, err = w.w.Write(ending)
+		if err != nil {
+			return written, err
+		}
+		w.cr = false
+	}
+
+	return written, nil
+}
+
+func cutLine(b []byte, max int) ([]byte, []byte) {
+	for i := 0; i < len(b); i++ {
+		if b[i] == '\r' && i == max {
+			continue
+		}
+		if b[i] == '\n' {
+			return b[:i+1], b[i+1:]
+		}
+		if i >= max {
+			return b[:i], b[i:]
+		}
+	}
+	return b, nil
+}
diff --git a/encoding_test.go b/encoding_test.go
@@ -71,3 +71,99 @@ func TestEncode(t *testing.T) {
 		}
 	}
 }
+
+var lineWrapperTests = []struct {
+	name    string
+	in, out string
+}{
+	{
+		name: "empty",
+		in:   "",
+		out:  "",
+	},
+	{
+		name: "oneLine",
+		in:   "ab",
+		out:  "ab",
+	},
+	{
+		name: "oneLineMax",
+		in:   "abc",
+		out:  "abc",
+	},
+	{
+		name: "twoLines",
+		in:   "abcde",
+		out:  "abc\r\nde",
+	},
+	{
+		name: "twoLinesMax",
+		in:   "abcdef",
+		out:  "abc\r\ndef",
+	},
+	{
+		name: "threeLines",
+		in:   "abcdefhi",
+		out:  "abc\r\ndef\r\nhi",
+	},
+	{
+		name: "wrappedMiss",
+		in:   "abcd\nef",
+		out:  "abc\r\nd\r\nef",
+	},
+	{
+		name: "wrappedLF",
+		in:   "abc\ndef\nhij",
+		out:  "abc\r\ndef\r\nhij",
+	},
+	{
+		name: "wrappedCRLF",
+		in:   "abc\r\ndef\r\nhij",
+		out:  "abc\r\ndef\r\nhij",
+	},
+	{
+		name: "trailingCRLF",
+		in:   "a\r\n",
+		out:  "a\r\n",
+	},
+	{
+		name: "cr",
+		in:   "\r\r\r\r\r",
+		out:  "\r\r\r\r\n\r",
+	},
+}
+
+func TestLineWrapper(t *testing.T) {
+	for _, tc := range lineWrapperTests {
+		t.Run(tc.name, func(t *testing.T) {
+			var sb strings.Builder
+			w := &lineWrapper{w: &sb, maxLineLen: 3}
+			if _, err := io.WriteString(w, tc.in); err != nil {
+				t.Fatalf("WriteString() = %v", err)
+			}
+			if s := sb.String(); s != tc.out {
+				t.Errorf("got %q, want %q", s, tc.out)
+			}
+		})
+
+		t.Run(tc.name+"/bytePerByte", func(t *testing.T) {
+			var sb strings.Builder
+			w := &lineWrapper{w: &sb, maxLineLen: 3}
+			if err := writeStringBytePerByte(w, tc.in); err != nil {
+				t.Fatalf("writeStringBytePerByte() = %v", err)
+			}
+			if s := sb.String(); s != tc.out {
+				t.Errorf("got %q, want %q", s, tc.out)
+			}
+		})
+	}
+}
+
+func writeStringBytePerByte(w io.Writer, s string) error {
+	for i := 0; i < len(s); i++ {
+		if _, err := w.Write([]byte{s[i]}); err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/go.mod b/go.mod
@@ -2,7 +2,4 @@ module github.com/emersion/go-message
 
 go 1.14
 
-require (
-	github.com/emersion/go-textwrapper v0.0.0-20200911093747-65d896831594
-	golang.org/x/text v0.14.0
-)
+require golang.org/x/text v0.14.0
diff --git a/go.sum b/go.sum
@@ -1,5 +1,3 @@
-github.com/emersion/go-textwrapper v0.0.0-20200911093747-65d896831594 h1:IbFBtwoTQyw0fIM5xv1HF+Y+3ZijDR839WMulgxCcUY=
-github.com/emersion/go-textwrapper v0.0.0-20200911093747-65d896831594/go.mod h1:aqO8z8wPrjkscevZJFVE1wXJrLpC5LtJG7fqLOsPb2U=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=