func writeHeader(w xo.Writer, fields Fields) error {
for _, f := range fields {
buf, err := w.Reserve(len(f.Name) + len(f.Value) + 4)
if err != nil {
return err
}
n := copy(buf[0:], f.Name)
n += copy(buf[n:], ": ")
n += copy(buf[n:], f.Value)
n += copy(buf[n:], "\r\n")
if err := w.Commit(n); err != nil {
return err
}
}
_, err := w.Write(crlf)
return err
}
