content: /*
   * Copyright (C) 2020 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.metadata;
  
  import androidx.annotation.Nullable;
  import com.google.android.exoplayer2.util.Assertions;
  import java.nio.ByteBuffer;
  
  /**
   * A {@link MetadataDecoder} base class that validates input buffers and discards any for which
   * {@link MetadataInputBuffer#isDecodeOnly()} is {@code true}.
   */
  public abstract class SimpleMetadataDecoder implements MetadataDecoder {
  
    @Override
    @Nullable
    public final Metadata decode(MetadataInputBuffer inputBuffer) {
      ByteBuffer buffer = Assertions.checkNotNull(inputBuffer.data);
      Assertions.checkArgument(
          buffer.position() == 0 && buffer.hasArray() && buffer.arrayOffset() == 0);
      return inputBuffer.isDecodeOnly() ? null : decode(inputBuffer, buffer);
    }
  
    /**
     * Called by {@link #decode(MetadataInputBuffer)} after input buffer validation has been
     * performed, except in the case that {@link MetadataInputBuffer#isDecodeOnly()} is {@code true}.
     *
     * @param inputBuffer The input buffer to decode.
     * @param buffer The input buffer's {@link MetadataInputBuffer#data data buffer}, for convenience.
     *     Validation by {@link #decode} guarantees that {@link ByteBuffer#hasArray()}, {@link
     *     ByteBuffer#position()} and {@link ByteBuffer#arrayOffset()} are {@code true}, {@code 0} and
     *     {@code 0} respectively.
     * @return The decoded metadata object, or {@code null} if the metadata could not be decoded.
     */
    @Nullable
    protected abstract Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer);
  }
  