Improving handling of atoms with size less than header in FragmentedMp4Extractor.

These currently lead to cryptic ArrayIndexOutOfBoundsExceptions being thrown from System.arraycopy() so my proposal is to throw a more useful ParserException instead.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=142087132

library/src/androidTest/java/com/google/android/exoplayer2/extractor/mp4/FragmentedMp4ExtractorTest.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.extractor.mp4;
 
 import android.test.InstrumentationTestCase;
+import com.google.android.exoplayer2.ParserException;
 import com.google.android.exoplayer2.extractor.Extractor;
 import com.google.android.exoplayer2.testutil.TestUtil;
 
@@ -24,13 +25,21 @@ import com.google.android.exoplayer2.testutil.TestUtil;
  */
 public final class FragmentedMp4ExtractorTest extends InstrumentationTestCase {
 
+  private static final TestUtil.ExtractorFactory EXTRACTOR_FACTORY =
+      new TestUtil.ExtractorFactory() {
+        @Override
+        public Extractor create() {
+          return new FragmentedMp4Extractor();
+        }
+      };
+
   public void testSample() throws Exception {
-    TestUtil.assertOutput(new TestUtil.ExtractorFactory() {
-      @Override
-      public Extractor create() {
-        return new FragmentedMp4Extractor();
-      }
-    }, "mp4/sample_fragmented.mp4", getInstrumentation());
+    TestUtil.assertOutput(EXTRACTOR_FACTORY, "mp4/sample_fragmented.mp4", getInstrumentation());
+  }
+
+  public void testAtomWithZeroSize() throws Exception {
+    TestUtil.assertThrows(EXTRACTOR_FACTORY, "mp4/sample_fragmented_zero_size_atom.mp4",
+        getInstrumentation(), ParserException.class);
   }
 
 }

library/src/main/java/com/google/android/exoplayer2/extractor/mp4/FragmentedMp4Extractor.java

@@ -257,6 +257,10 @@ public final class FragmentedMp4Extractor implements Extractor {
       atomSize = atomHeader.readUnsignedLongToLong();
     }
 
+    if (atomSize < atomHeaderBytesRead) {
+      throw new ParserException("Atom size less than header length (unsupported).");
+    }
+
     long atomPosition = input.getPosition() - atomHeaderBytesRead;
     if (atomType == Atom.TYPE_moof) {
       // The data positions may be updated when parsing the tfhd/trun.

testutils/src/main/java/com/google/android/exoplayer2/testutil/TestUtil.java

@@ -300,6 +300,81 @@ public class TestUtil {
     return extractorOutput;
   }
 
+  /**
+   * Calls {@link #assertThrows(Extractor, byte[], Class, boolean, boolean, boolean)} with all
+   * possible combinations of "simulate" parameters.
+   *
+   * @param factory An {@link ExtractorFactory} which creates instances of the {@link Extractor}
+   *     class which is to be tested.
+   * @param sampleFile The path to the input sample.
+   * @param instrumentation To be used to load the sample file.
+   * @param expectedThrowable Expected {@link Throwable} class.
+   * @throws IOException If reading from the input fails.
+   * @throws InterruptedException If interrupted while reading from the input.
+   * @see #assertThrows(Extractor, byte[], Class, boolean, boolean, boolean)
+   */
+  public static void assertThrows(ExtractorFactory factory, String sampleFile,
+      Instrumentation instrumentation, Class<? extends Throwable> expectedThrowable)
+      throws IOException, InterruptedException {
+    byte[] fileData = getByteArray(instrumentation, sampleFile);
+    assertThrows(factory, fileData, expectedThrowable);
+  }
+
+  /**
+   * Calls {@link #assertThrows(Extractor, byte[], Class, boolean, boolean, boolean)} with all
+   * possible combinations of "simulate" parameters.
+   *
+   * @param factory An {@link ExtractorFactory} which creates instances of the {@link Extractor}
+   *     class which is to be tested.
+   * @param fileData Content of the input file.
+   * @param expectedThrowable Expected {@link Throwable} class.
+   * @throws IOException If reading from the input fails.
+   * @throws InterruptedException If interrupted while reading from the input.
+   * @see #assertThrows(Extractor, byte[], Class, boolean, boolean, boolean)
+   */
+  public static void assertThrows(ExtractorFactory factory, byte[] fileData,
+      Class<? extends Throwable> expectedThrowable) throws IOException, InterruptedException {
+    assertThrows(factory.create(), fileData, expectedThrowable, false, false, false);
+    assertThrows(factory.create(), fileData, expectedThrowable,  true, false, false);
+    assertThrows(factory.create(), fileData, expectedThrowable, false,  true, false);
+    assertThrows(factory.create(), fileData, expectedThrowable,  true,  true, false);
+    assertThrows(factory.create(), fileData, expectedThrowable, false, false,  true);
+    assertThrows(factory.create(), fileData, expectedThrowable,  true, false,  true);
+    assertThrows(factory.create(), fileData, expectedThrowable, false,  true,  true);
+    assertThrows(factory.create(), fileData, expectedThrowable,  true,  true,  true);
+  }
+
+  /**
+   * Asserts {@code extractor} throws {@code expectedThrowable} while consuming {@code sampleFile}.
+   *
+   * @param extractor The {@link Extractor} to be tested.
+   * @param fileData Content of the input file.
+   * @param expectedThrowable Expected {@link Throwable} class.
+   * @param simulateIOErrors If true simulates IOErrors.
+   * @param simulateUnknownLength If true simulates unknown input length.
+   * @param simulatePartialReads If true simulates partial reads.
+   * @throws IOException If reading from the input fails.
+   * @throws InterruptedException If interrupted while reading from the input.
+   */
+  public static void assertThrows(Extractor extractor, byte[] fileData,
+      Class<? extends Throwable> expectedThrowable, boolean simulateIOErrors,
+      boolean simulateUnknownLength, boolean simulatePartialReads) throws IOException,
+      InterruptedException {
+    FakeExtractorInput input = new FakeExtractorInput.Builder().setData(fileData)
+        .setSimulateIOErrors(simulateIOErrors)
+        .setSimulateUnknownLength(simulateUnknownLength)
+        .setSimulatePartialReads(simulatePartialReads).build();
+    try {
+      consumeTestData(extractor, input, 0, true);
+      throw new AssertionError(expectedThrowable.getSimpleName() + " expected but not thrown");
+    } catch (Throwable throwable) {
+      if (expectedThrowable.equals(throwable.getClass())) {
+        return; // Pass!
+      }
+      throw throwable;
+    }
+  }
+
   public static void recursiveDelete(File fileOrDirectory) {
     if (fileOrDirectory.isDirectory()) {
       for (File child : fileOrDirectory.listFiles()) {