// sendReadRequest send RRQ to server and negotiates transfer options
//
// If the server doesn't support options and responds with data, the data will be added
// to rxBuf.
func (c *conn) sendReadRequest(filename string, opts map[string]string) error {
// Build RRQ
c.tx.writeReadReq(filename, c.mode, opts)
// Send request
if err := c.sendRequest(); err != nil {
return wrapError(err, "sending RRQ")
}
// Should have received OACK if server supports options, or DATA if not
switch op := c.rx.opcode(); op {
case opCodeOACK:
// Got OACK, parse options
if err := c.readSetup(); err != nil {
return wrapError(err, "got OACK, read setup")
}
case opCodeDATA:
// Server doesn't support options,
// write data to the buf so it's available for reading
var writer io.Writer = &c.rxBuf
if c.mode == ModeNetASCII {
na := netascii.NewWriter(writer)
defer errorDefer(na.Flush, c.log, "error flushing netascii encoder")
writer = na
}
n, err := writer.Write(c.rx.data())
if err != nil {
return wrapError(err, "writing RRQ response data")
}
// Set optionsParsed
c.optionsParsed = true
// If less than blksize, we're done
if n < int(c.blksize) {
c.done = true
}
// Ack data
if err := c.sendAck(c.rx.block()); err != nil {
return wrapError(err, "sending ACK for RRQ DATA")
}
c.block = c.rx.block()
case opCodeERROR:
// Received an error
return wrapError(c.remoteError(), "RRQ OACK response")
default:
return wrapError(&errUnexpectedDatagram{dg: c.rx.String()}, "RRQ OACK response")
}
return nil
}
// Write implements io.Writer and wraps write().
//
// If mode is ModeNetASCII, wrap write() with netascii.EncodeWriter.
func (c *conn) Write(p []byte) (int, error) {
// Can't write if an error has been sent/received
if c.err != nil {
return 0, wrapError(c.err, "checking conn err before Write")
}
if c.mode == ModeNetASCII {
if c.netasciiEnc == nil {
c.netasciiEnc = netascii.NewWriter(writerFunc(c.write))
}
n, err := c.netasciiEnc.Write(p)
return n, wrapError(err, "writing through netascii encoder")
}
n, err := c.write(p)
return n, wrapError(err, "writing through standard writer")
}
