Add a peekFully overload with allowEndOfInput.

This is in preparation for removing BufferingInput,
and using peeking instead.

Also add tests for peeking with allowEndOfInput and
resetPeekPosition.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=111318236

library/src/androidTest/java/com/google/android/exoplayer/extractor/DefaultExtractorInputTest.java

@@ -301,6 +301,76 @@ public class DefaultExtractorInputTest extends TestCase {
     }
   }
 
+  public void testResetPeekPosition() throws IOException, InterruptedException {
+    DefaultExtractorInput input = createDefaultExtractorInput();
+    byte[] target = new byte[TEST_DATA.length];
+    input.peekFully(target, 0, TEST_DATA.length);
+
+    // Check that we read the whole of TEST_DATA.
+    assertTrue(Arrays.equals(TEST_DATA, target));
+    assertEquals(0, input.getPosition());
+
+    // Check that we can peek again after resetting.
+    input.resetPeekPosition();
+    byte[] target2 = new byte[TEST_DATA.length];
+    input.peekFully(target2, 0, TEST_DATA.length);
+    assertTrue(Arrays.equals(TEST_DATA, target2));
+
+    // Check that we fail with EOFException if we peek past the end of the input.
+    try {
+      input.peekFully(target, 0, 1);
+      fail();
+    } catch (EOFException e) {
+      // Expected.
+    }
+  }
+
+  public void testPeekFullyAtEndOfStreamWithAllowEndOfInputSucceeds()
+      throws IOException, InterruptedException {
+    DefaultExtractorInput input = createDefaultExtractorInput();
+    byte[] target = new byte[TEST_DATA.length];
+
+    // Check peeking up to the end of input succeeds.
+    assertTrue(input.peekFully(target, 0, TEST_DATA.length, true));
+
+    // Check peeking at the end of input with allowEndOfInput signals the end of input.
+    assertFalse(input.peekFully(target, 0, 1, true));
+  }
+
+  public void testPeekFullyAcrossEndOfInputWithAllowEndOfInputFails()
+      throws IOException, InterruptedException {
+    DefaultExtractorInput input = createDefaultExtractorInput();
+    byte[] target = new byte[TEST_DATA.length];
+
+    // Check peeking before the end of input with allowEndOfInput succeeds.
+    assertTrue(input.peekFully(target, 0, TEST_DATA.length - 1, true));
+
+    // Check peeking across the end of input with allowEndOfInput throws.
+    try {
+      input.peekFully(target, 0, 2, true);
+      fail();
+    } catch (EOFException e) {
+      // Expected.
+    }
+  }
+
+  public void testResetAndPeekFullyPastEndOfStreamWithAllowEndOfInputFails()
+      throws IOException, InterruptedException {
+    DefaultExtractorInput input = createDefaultExtractorInput();
+    byte[] target = new byte[TEST_DATA.length];
+
+    // Check peeking up to the end of input succeeds.
+    assertTrue(input.peekFully(target, 0, TEST_DATA.length, true));
+    input.resetPeekPosition();
+    try {
+      // Check peeking one more byte throws.
+      input.peekFully(target, 0, TEST_DATA.length + 1, true);
+      fail();
+    } catch (EOFException e) {
+      // Expected.
+    }
+  }
+
   private static FakeDataSource buildDataSource() throws IOException {
     FakeDataSource.Builder builder = new FakeDataSource.Builder();
     builder.appendReadData(Arrays.copyOfRange(TEST_DATA, 0, 3));

library/src/main/java/com/google/android/exoplayer/extractor/DefaultExtractorInput.java

@@ -103,21 +103,42 @@ public final class DefaultExtractorInput implements ExtractorInput {
     skipFully(length, false);
   }
 
+  @Override
+  public boolean peekFully(byte[] target, int offset, int length, boolean allowEndOfInput)
+      throws IOException, InterruptedException {
+    if (!advancePeekPosition(length, allowEndOfInput)) {
+      return false;
+    }
+    System.arraycopy(peekBuffer, peekBufferPosition - length, target, offset, length);
+    return true;
+  }
+
   @Override
   public void peekFully(byte[] target, int offset, int length)
       throws IOException, InterruptedException {
-    advancePeekPosition(length);
-    System.arraycopy(peekBuffer, peekBufferPosition - length, target, offset, length);
+    peekFully(target, offset, length, false);
+  }
+
+  @Override
+  public boolean advancePeekPosition(int length, boolean allowEndOfInput)
+      throws IOException, InterruptedException {
+    ensureSpaceForPeek(length);
+    int bytesPeeked = Math.min(peekBufferLength - peekBufferPosition, length);
+    peekBufferLength += length - bytesPeeked;
+    while (bytesPeeked < length) {
+      bytesPeeked = readFromDataSource(peekBuffer, peekBufferPosition, length, bytesPeeked,
+          allowEndOfInput);
+      if (bytesPeeked == C.RESULT_END_OF_INPUT) {
+        return false;
+      }
+    }
+    peekBufferPosition += length;
+    return true;
   }
 
   @Override
   public void advancePeekPosition(int length) throws IOException, InterruptedException {
-    ensureSpaceForPeek(length);
-    peekBufferPosition += length;
-    while (peekBufferPosition > peekBufferLength) {
-      peekBufferLength = readFromDataSource(peekBuffer, 0, peekBufferPosition, peekBufferLength,
-          false);
-    }
+    advancePeekPosition(length, false);
   }
 
   @Override

library/src/main/java/com/google/android/exoplayer/extractor/ExtractorInput.java

@@ -123,8 +123,38 @@ public interface ExtractorInput {
    * Peeks {@code length} bytes from the peek position, writing them into {@code target} at index
    * {@code offset}. The current read position is left unchanged.
    * <p>
+   * If the end of the input is found having peeked no data, then behavior is dependent on
+   * {@code allowEndOfInput}. If {@code allowEndOfInput == true} then {@code false} is returned.
+   * Otherwise an {@link EOFException} is thrown.
+   * <p>
    * Calling {@link #resetPeekPosition()} resets the peek position to equal the current read
-   * position, so the caller can peek the same data again. Reading also resets the peek position.
+   * position, so the caller can peek the same data again. Reading and skipping also reset the peek
+   * position.
+   *
+   * @param target A target array into which data should be written.
+   * @param offset The offset into the target array at which to write.
+   * @param length The number of bytes to peek from the input.
+   * @param allowEndOfInput True if encountering the end of the input having peeked no data is
+   *     allowed, and should result in {@code false} being returned. False if it should be
+   *     considered an error, causing an {@link EOFException} to be thrown.
+   * @return True if the peek was successful. False if the end of the input was encountered having
+   *     peeked no data.
+   * @throws EOFException If the end of input was encountered having partially satisfied the peek
+   *     (i.e. having peeked at least one byte, but fewer than {@code length}), or if no bytes were
+   *     peeked and {@code allowEndOfInput} is false.
+   * @throws IOException If an error occurs peeking from the input.
+   * @throws InterruptedException If the thread is interrupted.
+   */
+  boolean peekFully(byte[] target, int offset, int length, boolean allowEndOfInput)
+      throws IOException, InterruptedException;
+
+  /**
+   * Peeks {@code length} bytes from the peek position, writing them into {@code target} at index
+   * {@code offset}. The current read position is left unchanged.
+   * <p>
+   * Calling {@link #resetPeekPosition()} resets the peek position to equal the current read
+   * position, so the caller can peek the same data again. Reading and skipping also reset the peek
+   * position.
    *
    * @param target A target array into which data should be written.
    * @param offset The offset into the target array at which to write.
@@ -135,6 +165,28 @@ public interface ExtractorInput {
    */
   void peekFully(byte[] target, int offset, int length) throws IOException, InterruptedException;
 
+  /**
+   * Advances the peek position by {@code length} bytes.
+   * <p>
+   * If the end of the input is encountered before advancing the peek position, then behavior is
+   * dependent on {@code allowEndOfInput}. If {@code allowEndOfInput == true} then {@code false} is
+   * returned. Otherwise an {@link EOFException} is thrown.
+   *
+   * @param length The number of bytes by which to advance the peek position.
+   * @param allowEndOfInput True if encountering the end of the input before advancing is allowed,
+   *     and should result in {@code false} being returned. False if it should be considered an
+   *     error, causing an {@link EOFException} to be thrown.
+   * @return True if advancing the peek position was successful. False if the end of the input was
+   *     encountered before the peek position could be advanced.
+   * @throws EOFException If the end of input was encountered having partially advanced (i.e. having
+   *     advanced by at least one byte, but fewer than {@code length}), or if the end of input was
+   *     encountered before advancing and {@code allowEndOfInput} is false.
+   * @throws IOException If an error occurs advancing the peek position.
+   * @throws InterruptedException If the thread is interrupted.
+   */
+  boolean advancePeekPosition(int length, boolean allowEndOfInput)
+      throws IOException, InterruptedException;
+
   /**
    * Advances the peek position by {@code length} bytes.
    *