Reuse temporary files (fixes #4)

internal/model/puller.go

@@ -412,12 +412,62 @@ func (p *Puller) handleFile(file protocol.FileInfo, copyChan chan<- copyBlocksSt
 	tempName := filepath.Join(p.dir, defTempNamer.TempName(file.Name))
 	realName := filepath.Join(p.dir, file.Name)
 
+	var reuse bool
+
+	// Check for an old temporary file which might have some blocks we could
+	// reuse.
+	tempBlocks, err := scanner.HashFile(tempName, protocol.BlockSize)
+	if err == nil {
+		// Check for any reusable blocks in the temp file
+		tempCopyBlocks, _ := scanner.BlockDiff(tempBlocks, file.Blocks)
+
+		// block.String() returns a string unique to the block
+		existingBlocks := make(map[string]bool, len(tempCopyBlocks))
+		for _, block := range tempCopyBlocks {
+			existingBlocks[block.String()] = true
+		}
+
+		// Since the blocks are already there, we don't need to copy them
+		// nor we need to pull them, hence discard blocks which are already
+		// there, if they are exactly the same...
+		var newCopyBlocks []protocol.BlockInfo
+		for _, block := range copyBlocks {
+			_, ok := existingBlocks[block.String()]
+			if !ok {
+				newCopyBlocks = append(newCopyBlocks, block)
+			}
+		}
+
+		var newPullBlocks []protocol.BlockInfo
+		for _, block := range pullBlocks {
+			_, ok := existingBlocks[block.String()]
+			if !ok {
+				newPullBlocks = append(newPullBlocks, block)
+			}
+		}
+
+		// If any blocks could be reused, let the sharedpullerstate know
+		// which flags it is expected to set on the file.
+		// Also update the list of work for the routines.
+		if len(copyBlocks) != len(newCopyBlocks) || len(pullBlocks) != len(newPullBlocks) {
+			reuse = true
+			copyBlocks = newCopyBlocks
+			pullBlocks = newPullBlocks
+		} else {
+			// Otherwise, discard the file ourselves in order for the
+			// sharedpuller not to panic when it fails to exlusively create a
+			// file which already exists
+			os.Remove(tempName)
+		}
+	}
+
 	s := sharedPullerState{
 		file:       file,
 		folder:     p.folder,
 		tempName:   tempName,
 		realName:   realName,
 		pullNeeded: len(pullBlocks),
+		reuse:      reuse,
 	}
 	if len(copyBlocks) > 0 {
 		s.copyNeeded = 1
@@ -628,12 +678,14 @@ func (p *Puller) finisherRoutine(in <-chan *sharedPullerState) {
 
 // clean deletes orphaned temporary files
 func (p *Puller) clean() {
+	keep := time.Duration(p.model.cfg.Options.KeepTemporariesH) * time.Hour
+	now := time.Now()
 	filepath.Walk(p.dir, func(path string, info os.FileInfo, err error) error {
 		if err != nil {
 			return err
 		}
 
-		if info.Mode().IsRegular() && defTempNamer.IsTemporary(path) {
+		if info.Mode().IsRegular() && defTempNamer.IsTemporary(path) && info.ModTime().Add(keep).Before(now) {
 			os.Remove(path)
 		}