Don't pass maxCacheFileSize to CacheEvictor if real size is unknown

CacheEvictor.onStartFile currently receives a length, which is the
maximum size of the content that might be written. The LRU cache
evictor will make sure there's sufficient space for the specified
size. If the actual size of the content is unknown, CacheDataSink
passes maxCacheFileSize.

The current behavior isn't ideal. It seems valid for a developer to
specify maxCacheFileSize=Long.MAX_VALUE if they don't want any
file fragmentation in the cache. However if they then attempt to
cache something with unknown length, LRU cache will try and make
room for content of length Long.MAX_VALUE, and end up evicting the
entire cache to do so.

This change alters the logic so a length is only passed if the
actual size of the content is known. In other cases C.LENGTH_UNSET
is now passed. The LRU evictor will not evict until after the file
is committed. Note a custom LRU evictor could still opt to evict to
ensure some application specified amount of space, if that's the
desired behavior.

PiperOrigin-RevId: 227509525

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

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer2.upstream.cache;
 
 import android.support.annotation.Nullable;
+import com.google.android.exoplayer2.C;
 import java.io.File;
 import java.io.IOException;
 import java.util.NavigableSet;
@@ -169,12 +170,12 @@ public interface Cache {
    *
    * @param key The cache key for the data.
    * @param position The starting position of the data.
-   * @param maxLength The maximum length of the data to be written. Used only to ensure that there
-   *     is enough space in the cache.
+   * @param length The length of the data being written, or {@link C#LENGTH_UNSET} if unknown. Used
+   *     only to ensure that there is enough space in the cache.
    * @return The file into which data should be written.
    * @throws CacheException If an error is encountered.
    */
-  File startFile(String key, long position, long maxLength) throws CacheException;
+  File startFile(String key, long position, long length) throws CacheException;
 
   /**
    * Commits a file into the cache. Must only be called when holding a corresponding hole {@link

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

@@ -170,10 +170,13 @@ public final class CacheDataSink implements DataSink {
   }
 
   private void openNextOutputStream() throws IOException {
-    long maxLength = dataSpec.length == C.LENGTH_UNSET ? maxCacheFileSize
-        : Math.min(dataSpec.length - dataSpecBytesWritten, maxCacheFileSize);
-    file = cache.startFile(dataSpec.key, dataSpec.absoluteStreamPosition + dataSpecBytesWritten,
-        maxLength);
+    long length =
+        dataSpec.length == C.LENGTH_UNSET
+            ? C.LENGTH_UNSET
+            : Math.min(dataSpec.length - dataSpecBytesWritten, maxCacheFileSize);
+    file =
+        cache.startFile(
+            dataSpec.key, dataSpec.absoluteStreamPosition + dataSpecBytesWritten, length);
     underlyingFileOutputStream = new FileOutputStream(file);
     if (bufferSize > 0) {
       if (bufferedOutputStream == null) {

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

@@ -15,6 +15,8 @@
  */
 package com.google.android.exoplayer2.upstream.cache;
 
+import com.google.android.exoplayer2.C;
+
 /**
  * Evicts data from a {@link Cache}. Implementations should call {@link Cache#removeSpan(CacheSpan)}
  * to evict cache entries based on their eviction policies.
@@ -32,8 +34,7 @@ public interface CacheEvictor extends Cache.Listener {
    * @param cache The source of the event.
    * @param key The key being written.
    * @param position The starting position of the data being written.
-   * @param maxLength The maximum length of the data being written.
+   * @param length The length of the data being written, or {@link C#LENGTH_UNSET} if unknown.
    */
-  void onStartFile(Cache cache, String key, long position, long maxLength);
-
+  void onStartFile(Cache cache, String key, long position, long length);
 }

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

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.upstream.cache;
 
+import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.upstream.cache.Cache.CacheException;
 import java.util.Comparator;
 import java.util.TreeSet;
@@ -40,8 +41,10 @@ public final class LeastRecentlyUsedCacheEvictor implements CacheEvictor, Compar
   }
 
   @Override
-  public void onStartFile(Cache cache, String key, long position, long maxLength) {
-    evictCache(cache, maxLength);
+  public void onStartFile(Cache cache, String key, long position, long length) {
+    if (length != C.LENGTH_UNSET) {
+      evictCache(cache, length);
+    }
   }
 
   @Override

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

@@ -259,8 +259,7 @@ public final class SimpleCache implements Cache {
   }
 
   @Override
-  public synchronized File startFile(String key, long position, long maxLength)
-      throws CacheException {
+  public synchronized File startFile(String key, long position, long length) throws CacheException {
     Assertions.checkState(!released);
     CachedContent cachedContent = index.get(key);
     Assertions.checkNotNull(cachedContent);
@@ -270,7 +269,7 @@ public final class SimpleCache implements Cache {
       cacheDir.mkdirs();
       removeStaleSpans();
     }
-    evictor.onStartFile(this, key, position, maxLength);
+    evictor.onStartFile(this, key, position, length);
     return SimpleCacheSpan.getCacheFile(
         cacheDir, cachedContent.id, position, System.currentTimeMillis());
   }