Method handleFile

lib/model/folder_sendrecv.go:1122–1172

This is the flow of data and events here, I think... +-----------------------+ | | - - - - > ItemStarted | handleFile | - - - - > ItemFinished (on shortcuts) | | +-----------------------+ | | copyChan (copyBlocksState; unless shortcut taken) |

(ctx context.Context, file protocol.FileInfo, copyChan chan<- copyBlocksState)

// handleFile queues the copies and pulls as necessary for a single new or
// changed file.
func (f *sendReceiveFolder) handleFile(ctx context.Context, file protocol.FileInfo, copyChan chan<- copyBlocksState) error {
	curFile, hasCurFile, err := f.model.sdb.GetDeviceFile(f.folderID, protocol.LocalDeviceID, file.Name)
	if err != nil {
		return err
	}

	have, _ := blockDiff(curFile.Blocks, file.Blocks)

	tempName := fs.TempName(file.Name)

	populateOffsets(file.Blocks)

	blocks := append([]protocol.BlockInfo{}, file.Blocks...)
	reused := make([]int, 0, len(file.Blocks))

	if f.Type != config.FolderTypeReceiveEncrypted {
		blocks, reused = f.reuseBlocks(ctx, blocks, reused, file, tempName)
	}

	// The sharedpullerstate will know which flags to use when opening the
	// temp file depending if we are reusing any blocks or not.
	if len(reused) == 0 {
		// Otherwise, discard the file ourselves in order for the
		// sharedpuller not to panic when it fails to exclusively create a
		// file which already exists
		f.inWritableDir(f.mtimefs.Remove, tempName)
	}

	// Reorder blocks
	blocks = f.blockPullReorderer.Reorder(blocks)

	f.evLogger.Log(events.ItemStarted, map[string]string{
		"folder": f.folderID,
		"item":   file.Name,
		"type":   "file",
		"action": "update",
	})

	s := newSharedPullerState(file, f.mtimefs, f.folderID, tempName, blocks, reused, f.IgnorePerms || file.NoPermissions, hasCurFile, curFile, !f.DisableSparseFiles, !f.DisableFsync)

	f.sl.DebugContext(ctx, "Handling file", slogutil.FilePath(file.Name), "blocksToCopy", len(blocks), "reused", len(reused))

	cs := copyBlocksState{
		sharedPullerState: s,
		blocks:            blocks,
		have:              len(have),
	}

	copyChan <- cs
	return nil
}

func (f *sendReceiveFolder) reuseBlocks(ctx context.Context, blocks []protocol.BlockInfo, reused []int, file protocol.FileInfo, tempName string) ([]protocol.BlockInfo, []int) {
	// Check for an old temporary file which might have some blocks we could