From b6089758ffa7caf37749183119e0ddfc98e65dd3 Mon Sep 17 00:00:00 2001
From: olly <olly@google.com>
Date: Tue, 7 Sep 2021 14:27:02 +0100
Subject: [PATCH] Fix incorrect assertion in CacheDataSource

#minor-release
#exofixit

PiperOrigin-RevId: 395233639
---
 RELEASENOTES.md                               |  3 +++
 .../upstream/cache/CacheDataSource.java       |  4 ++--
 .../upstream/cache/CacheDataSourceTest.java   | 22 +++++++++++++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index e72169a16e..fe7021b519 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -14,6 +14,9 @@
     *   Remove `ExoPlayerLibraryInfo.GL_ASSERTIONS_ENABLED`. Use
         `GlUtil.glAssertionsEnabled` instead.
     *   Fix `FlagSet#equals` on API levels below 24.
+    *   Fix `NullPointerException` being thrown from `CacheDataSource` when
+        reading a fully cached resource with `DataSpec.position` equal to the
+        resource length.
 *   Extractors:
     *   Support TS packets without PTS flag
         ([#9294](https://github.com/google/ExoPlayer/issues/9294)).
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
index 931cdf4552..338d9cd2ac 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
@@ -597,14 +597,14 @@ public final class CacheDataSource implements DataSource {
 
   @Override
   public int read(byte[] buffer, int offset, int length) throws IOException {
-    DataSpec requestDataSpec = checkNotNull(this.requestDataSpec);
-    DataSpec currentDataSpec = checkNotNull(this.currentDataSpec);
     if (length == 0) {
       return 0;
     }
     if (bytesRemaining == 0) {
       return C.RESULT_END_OF_INPUT;
     }
+    DataSpec requestDataSpec = checkNotNull(this.requestDataSpec);
+    DataSpec currentDataSpec = checkNotNull(this.currentDataSpec);
     try {
       if (readPosition >= checkCachePosition) {
         openNextSource(requestDataSpec, true);
diff --git a/library/core/src/test/java/com/google/android/exoplayer2/upstream/cache/CacheDataSourceTest.java b/library/core/src/test/java/com/google/android/exoplayer2/upstream/cache/CacheDataSourceTest.java
index 705188f88e..eefc4eb8c4 100644
--- a/library/core/src/test/java/com/google/android/exoplayer2/upstream/cache/CacheDataSourceTest.java
+++ b/library/core/src/test/java/com/google/android/exoplayer2/upstream/cache/CacheDataSourceTest.java
@@ -124,6 +124,28 @@ public final class CacheDataSourceTest {
     assertCacheAndRead(boundedDataSpec, /* unknownLength= */ false);
   }
 
+  @Test
+  public void cacheAndReadFromLength_readsZeroBytes() throws Exception {
+    // Read and cache all data from upstream.
+    CacheDataSource cacheDataSource =
+        createCacheDataSource(
+            /* setReadException= */ false, /* unknownLength= */ false, /* cacheKeyFactory= */ null);
+    assertReadDataContentLength(
+        cacheDataSource,
+        unboundedDataSpec,
+        /* unknownLength= */ false,
+        /* customCacheKey= */ false);
+
+    // Read from position == length.
+    cacheDataSource =
+        createCacheDataSource(
+            /* setReadException= */ true, /* unknownLength= */ false, /* cacheKeyFactory= */ null);
+    assertReadData(
+        cacheDataSource,
+        unboundedDataSpec.buildUpon().setPosition(TEST_DATA.length).build(),
+        /* unknownLength= */ false);
+  }
+
   @Test
   public void propagatesHttpHeadersUpstream() throws Exception {
     CacheDataSource cacheDataSource =