lib/db, lib/model: Keep need stats in metadata (ref #5899) (#6413)

lib/model/devicedownloadstate.go

@@ -18,6 +18,7 @@ import (
 type deviceFolderFileDownloadState struct {
 	blockIndexes []int32
 	version      protocol.Vector
+	blockSize    int
 }
 
 // deviceFolderDownloadState holds current download state of all files that
@@ -62,10 +63,12 @@ func (p *deviceFolderDownloadState) Update(updates []protocol.FileDownloadProgre
 				local = deviceFolderFileDownloadState{
 					blockIndexes: update.BlockIndexes,
 					version:      update.Version,
+					blockSize:    int(update.BlockSize),
 				}
 			} else if !local.version.Equal(update.Version) {
 				local.blockIndexes = append(local.blockIndexes[:0], update.BlockIndexes...)
 				local.version = update.Version
+				local.blockSize = int(update.BlockSize)
 			} else {
 				local.blockIndexes = append(local.blockIndexes, update.BlockIndexes...)
 			}
@@ -74,6 +77,20 @@ func (p *deviceFolderDownloadState) Update(updates []protocol.FileDownloadProgre
 	}
 }
 
+func (p *deviceFolderDownloadState) BytesDownloaded() int64 {
+	var res int64
+	for _, state := range p.files {
+		// BlockSize is a new field introduced in 1.4.1, thus a fallback
+		// is required (will potentially underrepresent downloaded bytes).
+		if state.blockSize != 0 {
+			res += int64(len(state.blockIndexes) * state.blockSize)
+		} else {
+			res += int64(len(state.blockIndexes) * protocol.MinBlockSize)
+		}
+	}
+	return res
+}
+
 // GetBlockCounts returns a map filename -> number of blocks downloaded.
 func (p *deviceFolderDownloadState) GetBlockCounts() map[string]int {
 	p.mut.RLock()
@@ -150,6 +167,22 @@ func (t *deviceDownloadState) GetBlockCounts(folder string) map[string]int {
 	return nil
 }
 
+func (t *deviceDownloadState) BytesDownloaded(folder string) int64 {
+	if t == nil {
+		return 0
+	}
+
+	t.mut.RLock()
+	defer t.mut.RUnlock()
+
+	for name, state := range t.folders {
+		if name == folder {
+			return state.BytesDownloaded()
+		}
+	}
+	return 0
+}
+
 func newDeviceDownloadState() *deviceDownloadState {
 	return &deviceDownloadState{
 		mut:     sync.NewRWMutex(),