// readFromVDI returns the count of total reads the corresponding VDI was subject to
// along with the no. of failed attempts, with the last seen error.
func readFromVDI(vdi *picard.VDI, vdiChan <-chan *vdiData, delay time.Duration) (int, int, error) {
// size of the buffer should be equal to twice the size of
// random payload.
var buf [8]byte
var total, failed, offset int
var err error
for vdat := range vdiChan {
time.Sleep(delay)
total++
n, rerr := vdi.ReadAt(buf[:], offset)
if rerr != nil {
err = rerr
failed++
} else if !reflect.DeepEqual(vdat.payload, buf[:n]) {
// This will register the error within `err` at a high level scope
// and continue processing remaining reads increasing the count
// of failures.
err = fmt.Errorf("new payload does not match original. New: %+v, Old: %+v", vdat.payload, buf[:n])
failed++
} else {
log.Printf("Complete reading %d payloads", total)
}
offset += n
}
return total, failed, err
}
// writeToVDI sends data packets to the vdi interface upto the
// count number that is defined within the function. If there is
// an error, it returns the no. of packets sent until the error
// occurred.
func writeToVDI(vdi *picard.VDI, vdiChan chan<- *vdiData, count int) (int, error) {
defer close(vdiChan)
var offset int
for i := 0; i < count; i++ {
buf := randPayload()
if _, err := vdi.WriteAt(buf, offset); err != nil {
return i, err
}
vdiChan <- &vdiData{buf}
offset += len(buf)
}
return count, nil
}