pkg/ioutils: fix multireader SEEK_CUR branch

Before getReaderForOffset returned always nil and wrong offset.

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

2 files changed, 50 insertions, 12 deletions

diff --git a/pkg/ioutils/multireader.go b/pkg/ioutils/multireader.go
index 0d2d76b479..234999bc92 100644
--- a/pkg/ioutils/multireader.go
+++ b/pkg/ioutils/multireader.go
@@ -97,27 +97,24 @@ func (r *multiReadSeeker) Seek(offset int64, whence int) (int64, error) {
 }
 
 func (r *multiReadSeeker) getReaderForOffset(offset int64) (io.ReadSeeker, int64, error) {
-	var rdr io.ReadSeeker
-	var rdrOffset int64
 
-	for i, rdr := range r.readers {
-		offsetTo, err := r.getOffsetToReader(rdr)
+	var offsetTo int64
+
+	for _, rdr := range r.readers {
+		size, err := getReadSeekerSize(rdr)
 		if err != nil {
 			return nil, -1, err
 		}
-		if offsetTo > offset {
-			rdr = r.readers[i-1]
-			rdrOffset = offsetTo - offset
-			break
+		if offsetTo+size > offset {
+			return rdr, offset - offsetTo, nil
 		}
-
 		if rdr == r.readers[len(r.readers)-1] {
-			rdrOffset = offsetTo + offset
-			break
+			return rdr, offsetTo + offset, nil
 		}
+		offsetTo += size
 	}
 
-	return rdr, rdrOffset, nil
+	return nil, 0, nil
 }
 
 func (r *multiReadSeeker) getCurOffset() (int64, error) {
diff --git a/pkg/ioutils/multireader_test.go b/pkg/ioutils/multireader_test.go
index de495b56da..306f5b0e1f 100644
--- a/pkg/ioutils/multireader_test.go
+++ b/pkg/ioutils/multireader_test.go
@@ -147,3 +147,44 @@ func TestMultiReadSeekerNegativeSeek(t *testing.T) {
 		t.Fatalf("expected %q to be %q", string(buf), expected)
 	}
 }
+
+func TestMultiReadSeekerCurAfterSet(t *testing.T) {
+	str := "hello world"
+	s1 := strings.NewReader(str + " 1")
+	s2 := strings.NewReader(str + " 2")
+	s3 := strings.NewReader(str + " 3")
+	mr := MultiReadSeeker(s1, s2, s3)
+
+	mid := int64(s1.Len() + s2.Len()/2)
+
+	size, err := mr.Seek(mid, os.SEEK_SET)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if size != mid {
+		t.Fatalf("reader size does not match, got %d, expected %d", size, mid)
+	}
+
+	size, err = mr.Seek(3, os.SEEK_CUR)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if size != mid+3 {
+		t.Fatalf("reader size does not match, got %d, expected %d", size, mid+3)
+	}
+	size, err = mr.Seek(5, os.SEEK_CUR)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if size != mid+8 {
+		t.Fatalf("reader size does not match, got %d, expected %d", size, mid+8)
+	}
+
+	size, err = mr.Seek(10, os.SEEK_CUR)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if size != mid+18 {
+		t.Fatalf("reader size does not match, got %d, expected %d", size, mid+18)
+	}
+}