This is the v1 version, had the v2 before.

write.go

@@ -0,0 +1,255 @@
+package imap
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"strconv"
+	"time"
+	"unicode"
+)
+
+type flusher interface {
+	Flush() error
+}
+
+type (
+	// A raw string.
+	RawString string
+)
+
+type WriterTo interface {
+	WriteTo(w *Writer) error
+}
+
+func formatNumber(num uint32) string {
+	return strconv.FormatUint(uint64(num), 10)
+}
+
+// Convert a string list to a field list.
+func FormatStringList(list []string) (fields []interface{}) {
+	fields = make([]interface{}, len(list))
+	for i, v := range list {
+		fields[i] = v
+	}
+	return
+}
+
+// Check if a string is 8-bit clean.
+func isAscii(s string) bool {
+	for _, c := range s {
+		if c > unicode.MaxASCII || unicode.IsControl(c) {
+			return false
+		}
+	}
+	return true
+}
+
+// An IMAP writer.
+type Writer struct {
+	io.Writer
+
+	AllowAsyncLiterals bool
+
+	continues <-chan bool
+}
+
+// Helper function to write a string to w.
+func (w *Writer) writeString(s string) error {
+	_, err := io.WriteString(w.Writer, s)
+	return err
+}
+
+func (w *Writer) writeCrlf() error {
+	if err := w.writeString(crlf); err != nil {
+		return err
+	}
+
+	return w.Flush()
+}
+
+func (w *Writer) writeNumber(num uint32) error {
+	return w.writeString(formatNumber(num))
+}
+
+func (w *Writer) writeQuoted(s string) error {
+	return w.writeString(strconv.Quote(s))
+}
+
+func (w *Writer) writeQuotedOrLiteral(s string) error {
+	if !isAscii(s) {
+		// IMAP doesn't allow 8-bit data outside literals
+		return w.writeLiteral(bytes.NewBufferString(s))
+	}
+
+	return w.writeQuoted(s)
+}
+
+func (w *Writer) writeDateTime(t time.Time, layout string) error {
+	if t.IsZero() {
+		return w.writeString(nilAtom)
+	}
+	return w.writeQuoted(t.Format(layout))
+}
+
+func (w *Writer) writeFields(fields []interface{}) error {
+	for i, field := range fields {
+		if i > 0 { // Write separator
+			if err := w.writeString(string(sp)); err != nil {
+				return err
+			}
+		}
+
+		if err := w.writeField(field); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (w *Writer) writeList(fields []interface{}) error {
+	if err := w.writeString(string(listStart)); err != nil {
+		return err
+	}
+
+	if err := w.writeFields(fields); err != nil {
+		return err
+	}
+
+	return w.writeString(string(listEnd))
+}
+
+// LiteralLengthErr is returned when the Len() of the Literal object does not
+// match the actual length of the byte stream.
+type LiteralLengthErr struct {
+	Actual   int
+	Expected int
+}
+
+func (e LiteralLengthErr) Error() string {
+	return fmt.Sprintf("imap: size of Literal is not equal to Len() (%d != %d)", e.Expected, e.Actual)
+}
+
+func (w *Writer) writeLiteral(l Literal) error {
+	if l == nil {
+		return w.writeString(nilAtom)
+	}
+
+	unsyncLiteral := w.AllowAsyncLiterals && l.Len() <= 4096
+
+	header := string(literalStart) + strconv.Itoa(l.Len())
+	if unsyncLiteral {
+		header += string('+')
+	}
+	header += string(literalEnd) + crlf
+	if err := w.writeString(header); err != nil {
+		return err
+	}
+
+	// If a channel is available, wait for a continuation request before sending data
+	if !unsyncLiteral && w.continues != nil {
+		// Make sure to flush the writer, otherwise we may never receive a continuation request
+		if err := w.Flush(); err != nil {
+			return err
+		}
+
+		if !<-w.continues {
+			return fmt.Errorf("imap: cannot send literal: no continuation request received")
+		}
+	}
+
+	// In case of bufio.Buffer, it will be 0 after io.Copy.
+	literalLen := int64(l.Len())
+
+	n, err := io.CopyN(w, l, literalLen)
+	if err != nil {
+		if err == io.EOF && n != literalLen {
+			return LiteralLengthErr{int(n), l.Len()}
+		}
+		return err
+	}
+	extra, _ := io.Copy(ioutil.Discard, l)
+	if extra != 0 {
+		return LiteralLengthErr{int(n + extra), l.Len()}
+	}
+
+	return nil
+}
+
+func (w *Writer) writeField(field interface{}) error {
+	if field == nil {
+		return w.writeString(nilAtom)
+	}
+
+	switch field := field.(type) {
+	case RawString:
+		return w.writeString(string(field))
+	case string:
+		return w.writeQuotedOrLiteral(field)
+	case int:
+		return w.writeNumber(uint32(field))
+	case uint32:
+		return w.writeNumber(field)
+	case Literal:
+		return w.writeLiteral(field)
+	case []interface{}:
+		return w.writeList(field)
+	case envelopeDateTime:
+		return w.writeDateTime(time.Time(field), envelopeDateTimeLayout)
+	case searchDate:
+		return w.writeDateTime(time.Time(field), searchDateLayout)
+	case Date:
+		return w.writeDateTime(time.Time(field), DateLayout)
+	case DateTime:
+		return w.writeDateTime(time.Time(field), DateTimeLayout)
+	case time.Time:
+		return w.writeDateTime(field, DateTimeLayout)
+	case *SeqSet:
+		return w.writeString(field.String())
+	case *BodySectionName:
+		// Can contain spaces - that's why we don't just pass it as a string
+		return w.writeString(string(field.FetchItem()))
+	}
+
+	return fmt.Errorf("imap: cannot format field: %v", field)
+}
+
+func (w *Writer) writeRespCode(code StatusRespCode, args []interface{}) error {
+	if err := w.writeString(string(respCodeStart)); err != nil {
+		return err
+	}
+
+	fields := []interface{}{RawString(code)}
+	fields = append(fields, args...)
+
+	if err := w.writeFields(fields); err != nil {
+		return err
+	}
+
+	return w.writeString(string(respCodeEnd))
+}
+
+func (w *Writer) writeLine(fields ...interface{}) error {
+	if err := w.writeFields(fields); err != nil {
+		return err
+	}
+
+	return w.writeCrlf()
+}
+
+func (w *Writer) Flush() error {
+	if f, ok := w.Writer.(flusher); ok {
+		return f.Flush()
+	}
+	return nil
+}
+
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{Writer: w}
+}
+
+func NewClientWriter(w io.Writer, continues <-chan bool) *Writer {
+	return &Writer{Writer: w, continues: continues}
+}