Add DecryptableSampleQueueReader

Reads from a SampleQueue, associating each read format with a
DrmSession, if needed.

PiperOrigin-RevId: 254192562

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

@@ -0,0 +1,182 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.source;
+
+import android.os.Looper;
+import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.FormatHolder;
+import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
+import com.google.android.exoplayer2.drm.DrmInitData;
+import com.google.android.exoplayer2.drm.DrmSession;
+import com.google.android.exoplayer2.drm.DrmSessionManager;
+import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.util.Util;
+import java.io.IOException;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+
+/**
+ * Reads from a {@link SampleQueue} and attaches {@link DrmSession} references to the {@link Format
+ * Formats} of encrypted regions.
+ */
+public final class DecryptableSampleQueueReader {
+
+  private final SampleQueue upstream;
+  private final DrmSessionManager<?> sessionManager;
+  private final FormatHolder formatHolder;
+  private final boolean playClearSamplesWithoutKeys;
+  @MonotonicNonNull private Format currentFormat;
+  @Nullable private DrmSession<?> currentSession;
+
+  /**
+   * Creates a sample queue reader.
+   *
+   * @param upstream The {@link SampleQueue} from which the created reader will read samples.
+   * @param sessionManager The {@link DrmSessionManager} that will provide {@link DrmSession
+   *     DrmSessions} for the encrypted regions.
+   */
+  public DecryptableSampleQueueReader(SampleQueue upstream, DrmSessionManager<?> sessionManager) {
+    this.upstream = upstream;
+    this.sessionManager = sessionManager;
+    formatHolder = new FormatHolder();
+    playClearSamplesWithoutKeys =
+        (sessionManager.getFlags() & DrmSessionManager.FLAG_PLAY_CLEAR_SAMPLES_WITHOUT_KEYS) != 0;
+  }
+
+  /** Releases any resources acquired by this reader. */
+  public void release() {
+    if (currentSession != null) {
+      currentSession.releaseReference();
+      currentSession = null;
+    }
+  }
+
+  /**
+   * Throws an error that's preventing data from being read. Does nothing if no such error exists.
+   *
+   * @throws IOException The underlying error.
+   */
+  public void maybeThrowError() throws IOException {
+    if (currentSession != null && currentSession.getState() == DrmSession.STATE_ERROR) {
+      throw Assertions.checkNotNull(currentSession.getError());
+    }
+  }
+
+  /**
+   * Reads from the upstream {@link SampleQueue}, populating {@link FormatHolder#drmSession} if the
+   * current {@link Format#drmInitData} is not null.
+   *
+   * <p>This reader guarantees that any read results are usable by clients. An encrypted sample will
+   * only be returned along with a {@link FormatHolder#drmSession} that has available keys.
+   *
+   * @param outputFormatHolder A {@link FormatHolder} to populate in the case of reading a format.
+   *     {@link FormatHolder#drmSession} will be populated if the read format's {@link
+   *     Format#drmInitData} is not null.
+   * @param buffer A {@link DecoderInputBuffer} to populate in the case of reading a sample or the
+   *     end of the stream. If the end of the stream has been reached, the {@link
+   *     C#BUFFER_FLAG_END_OF_STREAM} flag will be set on the buffer. If a {@link
+   *     DecoderInputBuffer#isFlagsOnly() flags-only} buffer is passed, only the buffer flags may be
+   *     populated by this method and the read position of the queue will not change.
+   * @param formatRequired Whether the caller requires that the format of the stream be read even if
+   *     it's not changing. A sample will never be read if set to true, however it is still possible
+   *     for the end of stream or nothing to be read.
+   * @param loadingFinished True if an empty queue should be considered the end of the stream.
+   * @param decodeOnlyUntilUs If a buffer is read, the {@link C#BUFFER_FLAG_DECODE_ONLY} flag will
+   *     be set if the buffer's timestamp is less than this value.
+   * @return The result, which can be {@link C#RESULT_NOTHING_READ}, {@link C#RESULT_FORMAT_READ} or
+   *     {@link C#RESULT_BUFFER_READ}.
+   */
+  @SuppressWarnings("ReferenceEquality")
+  public int read(
+      FormatHolder outputFormatHolder,
+      DecoderInputBuffer buffer,
+      boolean formatRequired,
+      boolean loadingFinished,
+      long decodeOnlyUntilUs) {
+
+    boolean readFlagFormatRequired = false;
+    boolean readFlagAllowOnlyClearBuffers = false;
+    boolean onlyPropagateFormatChanges = false;
+
+    if (currentFormat == null || formatRequired) {
+      readFlagFormatRequired = true;
+    } else if (currentFormat.drmInitData != null
+        && Assertions.checkNotNull(currentSession).getState()
+            != DrmSession.STATE_OPENED_WITH_KEYS) {
+      if (playClearSamplesWithoutKeys) {
+        // Content is encrypted and keys are not available, but clear samples are ok for reading.
+        readFlagAllowOnlyClearBuffers = true;
+      } else {
+        // We must not read any samples, but we may still read a format or the end of stream.
+        // However, because the formatRequired argument is false, we should not propagate a read
+        // format unless it is different than the current format.
+        onlyPropagateFormatChanges = true;
+        readFlagFormatRequired = true;
+      }
+    }
+
+    int result =
+        upstream.read(
+            formatHolder,
+            buffer,
+            readFlagFormatRequired,
+            readFlagAllowOnlyClearBuffers,
+            loadingFinished,
+            decodeOnlyUntilUs);
+    if (result == C.RESULT_FORMAT_READ) {
+      if (onlyPropagateFormatChanges && currentFormat == formatHolder.format) {
+        return C.RESULT_NOTHING_READ;
+      }
+      onFormat(Assertions.checkNotNull(formatHolder.format));
+      // TODO: Remove once all Renderers and MediaSources have migrated to the new DRM model
+      // [Internal ref: b/129764794].
+      outputFormatHolder.includesDrmSession = true;
+      outputFormatHolder.format = formatHolder.format;
+      outputFormatHolder.drmSession = currentSession;
+    }
+    return result;
+  }
+
+  /**
+   * Updates the current format and manages any necessary DRM resources.
+   *
+   * @param format The format read from upstream.
+   */
+  private void onFormat(Format format) {
+    DrmInitData oldDrmInitData = currentFormat != null ? currentFormat.drmInitData : null;
+    currentFormat = format;
+    if (Util.areEqual(oldDrmInitData, format.drmInitData)) {
+      // Nothing to do.
+      return;
+    }
+
+    // Ensure we acquire the new session before releasing the previous one in case the same session
+    // can be used for both DrmInitData.
+    DrmSession<?> previousSession = currentSession;
+    DrmInitData drmInitData = currentFormat.drmInitData;
+    if (drmInitData != null) {
+      currentSession =
+          sessionManager.acquireSession(Assertions.checkNotNull(Looper.myLooper()), drmInitData);
+    } else {
+      currentSession = null;
+    }
+
+    if (previousSession != null) {
+      previousSession.releaseReference();
+    }
+  }
+}