DO NOT MERGE) ExifInterface: Make saveAttributes throw an exception before change

ExifInterface object can be created with a unsupported file format.
If saveAttribute is called with an unsupported file format, ExifInterface
makes the file corrupted. This CL prevents those cases by throwing
an exception before making any change on the file.

Bug: 30936376
Change-Id: I915f56b00ec9422b53591ac5534e070a1d6798e6
(cherry picked from commit 2ee53c8)

Author: Sungsoo

media/java/android/media/ExifInterface.java

@@ -1039,6 +1039,7 @@ private ExifTag(String name, int number, int primaryFormat, int secondaryFormat)
     private int mThumbnailOffset;
     private int mThumbnailLength;
     private byte[] mThumbnailBytes;
+    private boolean mIsSupportedFile;
 
     // Pattern to check non zero timestamp
     private static final Pattern sNonZeroTimePattern = Pattern.compile(".*[1-9].*");
@@ -1337,9 +1338,11 @@ private void loadAttributes() throws IOException {
         try {
             InputStream in = new FileInputStream(mFilename);
             getJpegAttributes(in);
+            mIsSupportedFile = true;
         } catch (IOException e) {
             // Ignore exceptions in order to keep the compatibility with the old versions of
             // ExifInterface.
+            mIsSupportedFile = false;
             Log.w(TAG, "Invalid image.", e);
         } finally {
             addDefaultValuesForCompatibility();
@@ -1368,6 +1371,10 @@ private void printAttributes() {
      * and make a single call rather than multiple calls for each attribute.
      */
     public void saveAttributes() throws IOException {
+        if (!mIsSupportedFile) {
+            throw new UnsupportedOperationException(
+                    "ExifInterface only supports saving attributes on JPEG formats.");
+        }
         // Keep the thumbnail in memory
         mThumbnailBytes = getThumbnail();