UF.IMAGEIO

UF (Use Freed) issues are reported when there is an attempt to use resources after they were released. The UF.IMAGEIO warning indicates an attempt to use an ImageIO stream after it was closed.

Example 1

Copy

17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
     public boolean canDecodeInput(ImageInputStream stream) {
         byte[] b = new byte[8];
         try {
             final long l = stream.length();
             if (l > 655335) {
                 return false;
             }
             stream.mark();
             stream.readFully(b);
             stream.reset();
         } catch (IOException e) {
             return false;
         } finally {
             try {
                 stream.close();
             } catch (IOException e) {
                 // do nothing
             }
         }
 
         // Cast unsigned character constants prior to comparison
         return (b[0] == (byte) 'm' && b[1] == (byte) 'y' &&
                 b[2] == (byte) 'f' && b[3] == (byte) 'o' &&
                 b[4] == (byte) 'r' && b[5] == (byte) 'm' &&
                 b[6] == (byte) 'a' && b[7] == (byte) 't');
     }
 
     public void decode(Object data) throws IOException {
         final ImageInputStream stream = ImageIO.createImageInputStream(data);
         if (canDecodeInput(stream)) {
             try {
                 final int[] colors = new int[(int) stream.length()];
                 for (int i = 0; i < colors.length; i++) {
                     colors[i] = stream.readInt();
                 }
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
 
     }

UF.IMAGEIO is reported for the snippet on line 48: image input stream 'stream' is used after it was closed on line 31.

Example 2

Copy

17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
     public boolean canDecodeInput(ImageInputStream stream) {
         byte[] b = new byte[8];
         try {
             final long l = stream.length();
             if (l > 655335) {
                 return false;
             }
             stream.mark();
             stream.readFully(b);
             stream.reset();
         } catch (IOException e) {
             return false;
         }
 
         // Cast unsigned character constants prior to comparison
         return (b[0] == (byte) 'm' && b[1] == (byte) 'y' &&
                 b[2] == (byte) 'f' && b[3] == (byte) 'o' &&
                 b[4] == (byte) 'r' && b[5] == (byte) 'm' &&
                 b[6] == (byte) 'a' && b[7] == (byte) 't');
     }
 
     public void decode(Object data) throws IOException {
         final ImageInputStream stream = ImageIO.createImageInputStream(data);
         try {
             if (canDecodeInput(stream)) {
                 try {
                     final int[] colors = new int[(int) stream.length()];
                     for (int i = 0; i < colors.length; i++) {
                         colors[i] = stream.readInt();
                     }
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
         } finally {
             stream.close();
         }
     }

The snippet from the previous section is fixed. Method 'canDecodeInput' no longer closes the stream. Now it is closed by the 'decode' method, which is the method that opened the stream. In general, it is good coding practice to release a resource with the same method that originally allocated the resource.