Remove most allocations in SampleQueue.release

SampleQueues may be released in the context of a finally block
after an out of memory error. Allocating in that scenario can
throw yet a new OutOfMemoryError. By safely releasing SampleQueue
memory, we increase the possibility of handling the error
gracefully.

PiperOrigin-RevId: 420859022

library/core/src/main/java/com/google/android/exoplayer2/source/SampleDataQueue.java

@@ -27,6 +27,7 @@ import com.google.android.exoplayer2.source.SampleQueue.SampleExtrasHolder;
 import com.google.android.exoplayer2.upstream.Allocation;
 import com.google.android.exoplayer2.upstream.Allocator;
 import com.google.android.exoplayer2.upstream.DataReader;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
 import java.io.EOFException;
@@ -79,6 +80,7 @@ import java.util.Arrays;
    *     discarded, or 0 if the queue is now empty.
    */
   public void discardUpstreamSampleBytes(long totalBytesWritten) {
+    Assertions.checkArgument(totalBytesWritten <= this.totalBytesWritten);
     this.totalBytesWritten = totalBytesWritten;
     if (this.totalBytesWritten == 0
         || this.totalBytesWritten == firstAllocationNode.startPosition) {
@@ -92,8 +94,8 @@ import java.util.Arrays;
       while (this.totalBytesWritten > lastNodeToKeep.endPosition) {
         lastNodeToKeep = lastNodeToKeep.next;
       }
-      // Discard all subsequent nodes.
-      AllocationNode firstNodeToDiscard = lastNodeToKeep.next;
+      // Discard all subsequent nodes. lastNodeToKeep is initialized, therefore next cannot be null.
+      AllocationNode firstNodeToDiscard = Assertions.checkNotNull(lastNodeToKeep.next);
       clearAllocationNodes(firstNodeToDiscard);
       // Reset the successor of the last node to be an uninitialized node.
       lastNodeToKeep.next = new AllocationNode(lastNodeToKeep.endPosition, allocationLength);
@@ -213,17 +215,8 @@ import java.util.Arrays;
     // Bulk release allocations for performance (it's significantly faster when using
     // DefaultAllocator because the allocator's lock only needs to be acquired and released once)
     // [Internal: See b/29542039].
-    int allocationCount =
-        (writeAllocationNode.allocation != null ? 1 : 0)
-            + ((int) (writeAllocationNode.startPosition - fromNode.startPosition)
-                / allocationLength);
-    Allocation[] allocationsToRelease = new Allocation[allocationCount];
-    AllocationNode currentNode = fromNode;
-    for (int i = 0; i < allocationsToRelease.length; i++) {
-      allocationsToRelease[i] = currentNode.allocation;
-      currentNode = currentNode.clear();
-    }
-    allocator.release(allocationsToRelease);
+    allocator.release(fromNode);
+    fromNode.clear();
   }
 
   /**
@@ -466,7 +459,7 @@ import java.util.Arrays;
   }
 
   /** A node in a linked list of {@link Allocation}s held by the output. */
-  private static final class AllocationNode {
+  private static final class AllocationNode implements Allocator.AllocationNode {
 
     /** The absolute position of the start of the data (inclusive). */
     public final long startPosition;
@@ -525,5 +518,22 @@ import java.util.Arrays;
       next = null;
       return temp;
     }
+
+    // AllocationChainNode implementation.
+
+    @Override
+    public Allocation getAllocation() {
+      return Assertions.checkNotNull(allocation);
+    }
+
+    @Override
+    @Nullable
+    public Allocator.AllocationNode next() {
+      if (next == null || next.allocation == null) {
+        return null;
+      } else {
+        return next;
+      }
+    }
   }
 }

library/core/src/main/java/com/google/android/exoplayer2/upstream/Allocator.java

@@ -15,9 +15,22 @@
  */
 package com.google.android.exoplayer2.upstream;
 
+import androidx.annotation.Nullable;
+
 /** A source of allocations. */
 public interface Allocator {
 
+  /** A node in a chain of {@link Allocation Allocations}. */
+  interface AllocationNode {
+
+    /** Returns the {@link Allocation} associated to this chain node. */
+    Allocation getAllocation();
+
+    /** Returns the next chain node, or {@code null} if this is the last node in the chain. */
+    @Nullable
+    AllocationNode next();
+  }
+
   /**
    * Obtain an {@link Allocation}.
    *
@@ -36,15 +49,23 @@ public interface Allocator {
   void release(Allocation allocation);
 
   /**
-   * Releases an array of {@link Allocation}s back to the allocator.
+   * Releases an array of {@link Allocation Allocations} back to the allocator.
    *
    * @param allocations The array of {@link Allocation}s being released.
    */
   void release(Allocation[] allocations);
 
+  /**
+   * Releases all {@link Allocation Allocations} in the chain starting at the given {@link
+   * AllocationNode}.
+   *
+   * <p>Implementations must not make memory allocations.
+   */
+  void release(AllocationNode allocationNode);
+
   /**
    * Hints to the allocator that it should make a best effort to release any excess {@link
-   * Allocation}s.
+   * Allocation Allocations}.
    */
   void trim();
 

library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultAllocator.java

@@ -128,6 +128,17 @@ public final class DefaultAllocator implements Allocator {
     notifyAll();
   }
 
+  @Override
+  public synchronized void release(@Nullable AllocationNode allocationNode) {
+    while (allocationNode != null) {
+      availableAllocations[availableCount++] = allocationNode.getAllocation();
+      allocatedCount--;
+      allocationNode = allocationNode.next();
+    }
+    // Wake up threads waiting for the allocated size to drop.
+    notifyAll();
+  }
+
   @Override
   public synchronized void trim() {
     int targetAllocationCount = Util.ceilDivide(targetBufferSize, individualAllocationSize);