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.")
}
// tcpWrite wraps tcp_write.
func (t *tcpClient) tcpWrite(chunk []byte) error {
clen := len(chunk)
cchunk := C.CString(string(chunk))
defer C.free(unsafe.Pointer(cchunk))
t.mu.Lock()
err_t := C.tcp_write(t.client.pcb, unsafe.Pointer(cchunk), C.uint16_t(clen), C.TCP_WRITE_FLAG_COPY)
t.mu.Unlock()
switch err_t {
case C.ERR_OK:
t.accWritten(uint64(clen))
return nil
case C.ERR_MEM:
return errBufferIsFull
}
return fmt.Errorf("C.tcp_write: %d", int(err_t))
}