Omci receive workaround for Adtran OLT-Sim, some preparations for OnuSwUpgrade

Signed-off-by: mpagenko <michael.pagenkopf@adtran.com>
Change-Id: Iceb5c2309d65bf2893105c7701125606ef9c095b
diff --git a/internal/pkg/onuadaptercore/adapter_download_manager.go b/internal/pkg/onuadaptercore/adapter_download_manager.go
new file mode 100644
index 0000000..660c1fe
--- /dev/null
+++ b/internal/pkg/onuadaptercore/adapter_download_manager.go
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2020-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//Package adaptercoreonu provides the utility for onu devices, flows and statistics
+package adaptercoreonu
+
+import (
+	"context"
+	"errors"
+	"sync"
+
+	//"time"
+
+	"github.com/opencord/voltha-protos/v4/go/voltha"
+
+	"github.com/opencord/voltha-lib-go/v4/pkg/log"
+)
+
+// ### downloadToAdapter related definitions  ####
+
+//not yet defined to go with sca..., later also some configure options ??
+//const defaultDownloadTimeout = 60 // (?) Seconds
+//const localImgPath = "/home/lcui/work/tmp"
+
+// ### downloadToAdapter  			    - end ####
+
+//adapterDownloadManager structure holds information needed for downloading to and storing images within the adapter
+type adapterDownloadManager struct {
+	mutexDownloadImageDsc sync.RWMutex
+	downloadImageDscSlice []*voltha.ImageDownload
+}
+
+//newAdapterDownloadManager constructor returns a new instance of a adapterDownloadManager
+//mib_db (as well as not inluded alarm_db not really used in this code? VERIFY!!)
+func newAdapterDownloadManager(ctx context.Context) *adapterDownloadManager {
+	logger.Debug(ctx, "init-adapterDownloadManager")
+	var localDnldMgr adapterDownloadManager
+	localDnldMgr.downloadImageDscSlice = make([]*voltha.ImageDownload, 0)
+
+	return &localDnldMgr
+}
+
+//imageExists returns true if the requested image already exists within the adapter
+func (dm *adapterDownloadManager) imageExists(ctx context.Context, apImageDsc *voltha.ImageDownload) bool {
+	logger.Debugw(ctx, "checking on existence of the image", log.Fields{"image-name": (*apImageDsc).Name})
+	dm.mutexDownloadImageDsc.RLock()
+	defer dm.mutexDownloadImageDsc.RUnlock()
+
+	for _, pDnldImgDsc := range dm.downloadImageDscSlice {
+		if (*pDnldImgDsc).Name == (*apImageDsc).Name {
+			//image found (by name)
+			return true
+		}
+	}
+	//image not found (by name)
+	return false
+}
+
+//startDownload returns true if the download of the requested image could be started
+func (dm *adapterDownloadManager) startDownload(ctx context.Context, apImageDsc *voltha.ImageDownload) error {
+	logger.Debugw(ctx, "image download requested", log.Fields{"image-name": apImageDsc.Name})
+	//so far just return error
+	return errors.New("could not start downloading")
+}