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69d2699961
As required by RFC 2045 (MIME). The 78 byte lines work in practice, except that SpamAssassin has rules that give messages with 78-byte lines spam points. Mentioned by kjetilho on irc.
72 lines
1.2 KiB
Go
72 lines
1.2 KiB
Go
package moxio
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import (
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"encoding/base64"
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"io"
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)
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// implement io.Closer
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type closerFunc func() error
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func (f closerFunc) Close() error {
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return f()
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}
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// Base64Writer turns a writer for data into one that writes base64 content on
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// \r\n separated lines of max 76+2 characters length.
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func Base64Writer(w io.Writer) io.WriteCloser {
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lw := &lineWrapper{w: w}
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bw := base64.NewEncoder(base64.StdEncoding, lw)
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return struct {
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io.Writer
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io.Closer
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}{
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Writer: bw,
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Closer: closerFunc(func() error {
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if err := bw.Close(); err != nil {
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return err
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}
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return lw.Close()
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}),
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}
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}
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type lineWrapper struct {
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w io.Writer
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n int // Written on current line.
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}
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func (lw *lineWrapper) Write(buf []byte) (int, error) {
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wrote := 0
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for len(buf) > 0 {
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// base64 has max 76 data bytes on per line. ../rfc/2045:1372
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n := min(76-lw.n, len(buf))
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nn, err := lw.w.Write(buf[:n])
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if nn > 0 {
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wrote += nn
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buf = buf[nn:]
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}
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if err != nil {
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return wrote, err
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}
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lw.n += nn
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if lw.n == 76 {
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_, err := lw.w.Write([]byte("\r\n"))
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if err != nil {
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return wrote, err
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}
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lw.n = 0
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}
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}
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return wrote, nil
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}
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func (lw *lineWrapper) Close() error {
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if lw.n > 0 {
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lw.n = 0
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_, err := lw.w.Write([]byte("\r\n"))
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return err
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}
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return nil
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}
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