copy/move: detect file size change during copy/move - fixes #1250

backend/local/local.go

@@ -651,10 +651,17 @@ type localOpenFile struct {
 	o    *Object           // object that is open
 	in   io.ReadCloser     // handle we are wrapping
 	hash *hash.MultiHasher // currently accumulating hashes
+	fd   *os.File          // file object reference
 }
 
 // Read bytes from the object - see io.Reader
 func (file *localOpenFile) Read(p []byte) (n int, err error) {
+	// Check if file has the same size and modTime
+	fi, err := file.fd.Stat()
+	if file.o.size != fi.Size() || file.o.modTime != fi.ModTime() {
+		return 0, errors.New("can't copy - source file is being updated")
+	}
+
 	n, err = file.in.Read(p)
 	if n > 0 {
 		// Hash routines never return an error
@@ -713,6 +720,7 @@ func (o *Object) Open(options ...fs.OpenOption) (in io.ReadCloser, err error) {
 		o:    o,
 		in:   wrappedFd,
 		hash: hash,
+		fd:   fd,
 	}
 	return in, nil
 }

backend/local/local_internal_test.go

@@ -1,11 +1,23 @@
 package local
 
 import (
+	"os"
+	"path"
 	"testing"
+	"time"
 
+	"github.com/ncw/rclone/fs/hash"
+	"github.com/ncw/rclone/fstest"
+	"github.com/ncw/rclone/lib/readers"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
+// TestMain drives the tests
+func TestMain(m *testing.M) {
+	fstest.TestMain(m)
+}
+
 func TestMapper(t *testing.T) {
 	m := newMapper()
 	assert.Equal(t, m.m, map[string]string{})
@@ -17,4 +29,34 @@ func TestMapper(t *testing.T) {
 	})
 	assert.Equal(t, "potato", m.Load("potato"))
 	assert.Equal(t, "-r?'a´o¨", m.Load("-r'áö"))
+
+	// Test copy with source file that's updating
+	r := fstest.NewRun(t)
+	defer r.Finalise()
+	filePath := "sub dir/local test"
+	r.WriteFile(filePath, "content", time.Now())
+
+	fd, err := os.Open(path.Join(r.LocalName, filePath))
+	if err != nil {
+		t.Fatalf("failed opening file %q: %v", filePath, err)
+	}
+
+	fi, err := fd.Stat()
+	o := &Object{size: fi.Size(), modTime: fi.ModTime()}
+	wrappedFd := readers.NewLimitedReadCloser(fd, -1)
+	hash, err := hash.NewMultiHasherTypes(hash.Supported)
+	in := localOpenFile{
+		o:    o,
+		in:   wrappedFd,
+		hash: hash,
+		fd:   fd,
+	}
+
+	buf := make([]byte, 1)
+	_, err = in.Read(buf)
+	require.NoError(t, err)
+
+	r.WriteFile(filePath, "content updated", time.Now())
+	_, err = in.Read(buf)
+	require.Errorf(t, err, "can't copy - source file is being updated")
 }