Update the DefaultExtractorInput's peek buffer length on each write

This prevents leaving an inconsistent state after a EOF exception.

Issue:google#5039

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=219785275

RELEASENOTES.md

@@ -18,8 +18,11 @@
   * Fix handling of streams with appended data
     ([#4954](https://github.com/google/ExoPlayer/issues/4954)).
 * DASH: Parse ProgramInformation element if present in the manifest.
-* HLS: Add constructor to `DefaultHlsExtractorFactory` for adding TS payload
-  reader factory flags
+* HLS:
+  * Add constructor to `DefaultHlsExtractorFactory` for adding TS payload
+    reader factory flags
+  * Fix bug in segment sniffing
+    ([#5039](https://github.com/google/ExoPlayer/issues/5039)).
   ([#4861](https://github.com/google/ExoPlayer/issues/4861)).
 * SubRip: Add support for alignment tags, and remove tags from the displayed
   captions ([#4306](https://github.com/google/ExoPlayer/issues/4306)).

library/core/src/main/java/com/google/android/exoplayer2/extractor/DefaultExtractorInput.java

@@ -130,16 +130,16 @@ public void peekFully(byte[] target, int offset, int length)
   public boolean advancePeekPosition(int length, boolean allowEndOfInput)
       throws IOException, InterruptedException {
     ensureSpaceForPeek(length);
-    int bytesPeeked = Math.min(peekBufferLength - peekBufferPosition, length);
+    int bytesPeeked = peekBufferLength - peekBufferPosition;
     while (bytesPeeked < length) {
       bytesPeeked = readFromDataSource(peekBuffer, peekBufferPosition, length, bytesPeeked,
           allowEndOfInput);
       if (bytesPeeked == C.RESULT_END_OF_INPUT) {
         return false;
       }
+      peekBufferLength = peekBufferPosition + bytesPeeked;
     }
     peekBufferPosition += length;
-    peekBufferLength = Math.max(peekBufferLength, peekBufferPosition);
     return true;
   }
 

library/core/src/test/java/com/google/android/exoplayer2/extractor/DefaultExtractorInputTest.java

@@ -338,6 +338,23 @@ public void testPeekFully() throws Exception {
     }
   }
 
+  @Test
+  public void testPeekFullyAfterEofExceptionPeeksAsExpected() throws Exception {
+    DefaultExtractorInput input = createDefaultExtractorInput();
+    byte[] target = new byte[TEST_DATA.length + 10];
+
+    try {
+      input.peekFully(target, /* offset= */ 0, target.length);
+      fail();
+    } catch (EOFException expected) {
+      // Do nothing. Expected.
+    }
+    input.peekFully(target, /* offset= */ 0, /* length= */ TEST_DATA.length);
+
+    assertThat(input.getPeekPosition()).isEqualTo(TEST_DATA.length);
+    assertThat(Arrays.equals(TEST_DATA, Arrays.copyOf(target, TEST_DATA.length))).isTrue();
+  }
+
   @Test
   public void testResetPeekPosition() throws Exception {
     DefaultExtractorInput input = createDefaultExtractorInput();