aboutsummaryrefslogtreecommitdiff
path: root/pkg/rfc822
diff options
context:
space:
mode:
Diffstat (limited to 'pkg/rfc822')
-rw-r--r--pkg/rfc822/writer.go72
-rw-r--r--pkg/rfc822/writer_test.go47
2 files changed, 119 insertions, 0 deletions
diff --git a/pkg/rfc822/writer.go b/pkg/rfc822/writer.go
new file mode 100644
index 0000000..07751ea
--- /dev/null
+++ b/pkg/rfc822/writer.go
@@ -0,0 +1,72 @@
+// Package rfc822 provides a writer that ensures the intrinsics of RFC 822.
+//
+// Rationale
+//
+// Cyrus IMAP really cares about the hard specifics of RFC 822, namely not allowing single \r and \n.
+//
+// See also: https://www.cyrusimap.org/imap/reference/faqs/interop-barenewlines.html
+// and: https://github.com/Necoro/feed2imap-go/issues/46
+//
+// NB: This package currently only cares about the newlines.
+package rfc822
+
+import "io"
+
+type rfc822Writer struct {
+ w io.Writer
+}
+
+var lf = []byte{'\n'}
+var cr = []byte{'\r'}
+
+func (f rfc822Writer) Write(p []byte) (n int, err error) {
+ crFound := false
+ start := 0
+
+ write := func(str []byte) {
+ var j int
+ j, err = f.w.Write(str)
+ n = n + j
+ }
+
+ for idx, b := range p {
+ if crFound && b != '\n' {
+ // insert '\n'
+ if write(p[start:idx]); err != nil {
+ return
+ }
+ if write(lf); err != nil {
+ return
+ }
+
+ start = idx
+ } else if !crFound && b == '\n' {
+ // insert '\r'
+ if write(p[start:idx]); err != nil {
+ return
+ }
+ if write(cr); err != nil {
+ return
+ }
+
+ start = idx
+ }
+ crFound = b == '\r'
+ }
+
+ // write the remainder
+ if write(p[start:]); err != nil {
+ return
+ }
+
+ if crFound { // dangling \r
+ write(lf)
+ }
+
+ return
+}
+
+// Writer creates a new RFC 822 conform writer.
+func Writer(w io.Writer) io.Writer {
+ return rfc822Writer{w}
+}
diff --git a/pkg/rfc822/writer_test.go b/pkg/rfc822/writer_test.go
new file mode 100644
index 0000000..7beae8d
--- /dev/null
+++ b/pkg/rfc822/writer_test.go
@@ -0,0 +1,47 @@
+package rfc822
+
+import (
+ "bytes"
+ "io"
+ "testing"
+)
+
+func TestRfc822Writer_Write(t *testing.T) {
+ tests := []struct {
+ before string
+ after string
+ }{
+ {"", ""},
+ {"foo", "foo"},
+ {"foo\r", "foo\r\n"},
+ {"foo\n", "foo\r\n"},
+ {"foo\r\n", "foo\r\n"},
+ {"\r", "\r\n"},
+ {"\n", "\r\n"},
+ {"\r\n", "\r\n"},
+ {"foo\rbar", "foo\r\nbar"},
+ {"foo\nbar", "foo\r\nbar"},
+ {"foo\r\nbar", "foo\r\nbar"},
+ {"\r\r", "\r\n\r\n"},
+ {"\n\n", "\r\n\r\n"},
+ {"\r\r\n", "\r\n\r\n"},
+ {"\n\r", "\r\n\r\n"},
+ {"\rbar", "\r\nbar"},
+ {"\nbar", "\r\nbar"},
+ {"\r\nbar", "\r\nbar"},
+ }
+ for _, tt := range tests {
+ t.Run(tt.before, func(t *testing.T) {
+ b := bytes.Buffer{}
+ w := Writer(&b)
+ if _, err := io.WriteString(w, tt.before); err != nil {
+ t.Errorf("Error: %v", err)
+ return
+ }
+ res := b.String()
+ if tt.after != res {
+ t.Errorf("Expected: %q, got: %q", tt.after, res)
+ }
+ })
+ }
+}