Break Archiver.SaveFile() method down into smaller ones

archiver.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/juju/arrar"
 	"github.com/restic/restic/backend"
+	"github.com/restic/restic/chunker"
 	"github.com/restic/restic/debug"
 	"github.com/restic/restic/pack"
 	"github.com/restic/restic/pipe"
@@ -88,65 +89,36 @@ func (arch *Archiver) SaveTreeJSON(item interface{}) (backend.ID, error) {
 	return arch.s.SaveJSON(pack.Tree, item)
 }
 
-// SaveFile stores the content of the file on the backend as a Blob by calling
-// Save for each chunk.
-func (arch *Archiver) SaveFile(p *Progress, node *Node) error {
-	file, err := node.OpenForReading()
-	defer file.Close()
-	if err != nil {
-		return err
-	}
-
-	// check file again, since it could have disappeared by now
+func (arch *Archiver) reloadFileIfChanged(node *Node, file *os.File) (*Node, error) {
 	fi, err := file.Stat()
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	if fi.ModTime() != node.ModTime {
-		e2 := arch.Error(node.path, fi, errors.New("file was updated, using new version"))
+	if fi.ModTime() == node.ModTime {
+		return node, nil
+	}
 
-		if e2 == nil {
-			n, err := NodeFromFileInfo(node.path, fi)
+	err = arch.Error(node.path, fi, errors.New("file has changed"))
+	if err != nil {
+		return nil, err
+	}
+
+	node, err = NodeFromFileInfo(node.path, fi)
 	if err != nil {
 		debug.Log("Archiver.SaveFile", "NodeFromFileInfo returned error for %v: %v", node.path, err)
-				return err
+		return nil, err
 	}
 
-			*node = *n
-		}
+	return node, nil
 }
 
-	type result struct {
+type saveResult struct {
 	id    backend.ID
 	bytes uint64
 }
 
-	// store all chunks
-	chnker := GetChunker("archiver.SaveFile")
-	chnker.Reset(file, arch.s.ChunkerPolynomial())
-	chans := [](<-chan result){}
-	defer FreeChunker("archiver.SaveFile", chnker)
-
-	chunks := 0
-
-	for {
-		chunk, err := chnker.Next()
-		if err == io.EOF {
-			break
-		}
-
-		if err != nil {
-			return arrar.Annotate(err, "SaveFile() chunker.Next()")
-		}
-
-		chunks++
-
-		// acquire token, start goroutine to save chunk
-		token := <-arch.blobToken
-		resCh := make(chan result, 1)
-
-		go func(ch chan<- result) {
+func (arch *Archiver) saveChunk(chunk *chunker.Chunk, p *Progress, token struct{}, file *os.File, resultChannel chan<- saveResult) {
 	err := arch.Save(pack.Data, chunk.Digest, chunk.Length, chunk.Reader(file))
 	// TODO handle error
 	if err != nil {
@@ -155,25 +127,29 @@ func (arch *Archiver) SaveFile(p *Progress, node *Node) error {
 
 	p.Report(Stat{Bytes: uint64(chunk.Length)})
 	arch.blobToken <- token
-			ch <- result{id: backend.ID(chunk.Digest), bytes: uint64(chunk.Length)}
-		}(resCh)
-
-		chans = append(chans, resCh)
+	resultChannel <- saveResult{id: backend.ID(chunk.Digest), bytes: uint64(chunk.Length)}
 }
 
-	results := []result{}
-	for _, ch := range chans {
+func waitForResults(resultChannels [](<-chan saveResult)) ([]saveResult, error) {
+	results := []saveResult{}
+
+	for _, ch := range resultChannels {
 		results = append(results, <-ch)
 	}
 
-	if len(results) != chunks {
-		return fmt.Errorf("chunker returned %v chunks, but only %v blobs saved", chunks, len(results))
+	if len(results) != len(resultChannels) {
+		return nil, fmt.Errorf("chunker returned %v chunks, but only %v blobs saved", len(resultChannels), len(results))
 	}
 
-	var bytes uint64
+	return results, nil
+}
 
-	node.Content = make([]backend.ID, len(results))
+func updateNodeContent(node *Node, results []saveResult) error {
 	debug.Log("Archiver.Save", "checking size for file %s", node.path)
+
+	var bytes uint64
+	node.Content = make([]backend.ID, len(results))
+
 	for i, b := range results {
 		node.Content[i] = b.id
 		bytes += b.bytes
@@ -190,6 +166,49 @@ func (arch *Archiver) SaveFile(p *Progress, node *Node) error {
 	return nil
 }
 
+// SaveFile stores the content of the file on the backend as a Blob by calling
+// Save for each chunk.
+func (arch *Archiver) SaveFile(p *Progress, node *Node) error {
+	file, err := node.OpenForReading()
+	defer file.Close()
+	if err != nil {
+		return err
+	}
+
+	node, err = arch.reloadFileIfChanged(node, file)
+	if err != nil {
+		return err
+	}
+
+	chnker := GetChunker("archiver.SaveFile")
+	chnker.Reset(file, arch.s.ChunkerPolynomial())
+	resultChannels := [](<-chan saveResult){}
+	defer FreeChunker("archiver.SaveFile", chnker)
+
+	for {
+		chunk, err := chnker.Next()
+		if err == io.EOF {
+			break
+		}
+
+		if err != nil {
+			return arrar.Annotate(err, "SaveFile() chunker.Next()")
+		}
+
+		resCh := make(chan saveResult, 1)
+		go arch.saveChunk(chunk, p, <-arch.blobToken, file, resCh)
+		resultChannels = append(resultChannels, resCh)
+	}
+
+	results, err := waitForResults(resultChannels)
+	if err != nil {
+		return err
+	}
+
+	err = updateNodeContent(node, results)
+	return err
+}
+
 func (arch *Archiver) saveTree(p *Progress, t *Tree) (backend.ID, error) {
 	debug.Log("Archiver.saveTree", "saveTree(%v)\n", t)
 	var wg sync.WaitGroup