Prepare gpudemod batch runner for stream-backed slots

internal/demod/gpudemod/batch_runner.go

@@ -1,7 +1,15 @@
 package gpudemod
 
+type batchSlot struct {
+	job    ExtractJob
+	out    []complex64
+	rate   int
+	active bool
+}
+
 type BatchRunner struct {
-	eng *Engine
+	eng   *Engine
+	slots []batchSlot
 }
 
 func NewBatchRunner(maxSamples int, sampleRate int) (*BatchRunner, error) {
@@ -18,11 +26,39 @@ func (r *BatchRunner) Close() {
 	}
 	r.eng.Close()
 	r.eng = nil
+	r.slots = nil
+}
+
+func (r *BatchRunner) prepare(jobs []ExtractJob) {
+	if cap(r.slots) < len(jobs) {
+		r.slots = make([]batchSlot, len(jobs))
+	} else {
+		r.slots = r.slots[:len(jobs)]
+	}
+	for i, job := range jobs {
+		r.slots[i] = batchSlot{job: job, active: true}
+	}
 }
 
 func (r *BatchRunner) ShiftFilterDecimateBatch(iq []complex64, jobs []ExtractJob) ([][]complex64, []int, error) {
 	if r == nil || r.eng == nil {
 		return nil, nil, ErrUnavailable
 	}
-	return r.eng.ShiftFilterDecimateBatch(iq, jobs)
+	r.prepare(jobs)
+	outs := make([][]complex64, len(jobs))
+	rates := make([]int, len(jobs))
+	for i := range r.slots {
+		if !r.slots[i].active {
+			continue
+		}
+		out, rate, err := r.eng.ShiftFilterDecimate(iq, r.slots[i].job.OffsetHz, r.slots[i].job.BW, r.slots[i].job.OutRate)
+		if err != nil {
+			return nil, nil, err
+		}
+		r.slots[i].out = out
+		r.slots[i].rate = rate
+		outs[i] = out
+		rates[i] = rate
+	}
+	return outs, rates, nil
 }