func (t *tcpClient) enqueue(chunk []byte) error {
cchunk := C.CString(string(chunk))
defer C.free(unsafe.Pointer(cchunk))
sleepTime := time.Millisecond * 5
for j := 0; j < maxEnqueueAttempts; j++ {
err_t := C.tcp_write(t.client.pcb, unsafe.Pointer(cchunk), C.uint16_t(len(chunk)), 1)
if err_t == C.ERR_OK {
return nil
}
if err_t == C.ERR_MEM {
// Could not enqueue anymore, let's flush and try again.
err_t := C.tcp_output(t.client.pcb)
if err_t == C.ERR_OK {
// Last part was flushed, now continue and try again...
time.Sleep(sleepTime)
if sleepTime < maxWaitingTime {
sleepTime = sleepTime * 2
}
continue
}
return fmt.Errorf("tcp_output: %d", int(err_t))
}
}
return fmt.Errorf("Could not flush data. Giving up.")
}
func (t *tcpClient) flush() error {
for {
blen := t.outbuf.Len()
if blen > writeBufSize {
blen = writeBufSize
}
if blen == 0 {
break
}
chunk := make([]byte, blen)
if _, err := t.outbuf.Read(chunk); err != nil {
return err
}
if err := t.enqueue(chunk); err != nil {
return err
}
}
err_t := C.tcp_output(t.client.pcb)
if err_t != C.ERR_OK {
return fmt.Errorf("tcp_output: %d", int(err_t))
}
return nil
}
// tcpOutput wraps tcp_output.
func (t *tcpClient) tcpOutput() error {
t.mu.Lock()
err_t := C.tcp_output(t.client.pcb)
t.mu.Unlock()
if err_t != C.ERR_OK {
return fmt.Errorf("C.tcp_output: %d", int(err_t))
}
return nil
}