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|
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}
}
|
