content: /*
   * Copyright (C) 2017 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.emsg;
  
  import android.support.annotation.Nullable;
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.util.Assertions;
  import com.google.android.exoplayer2.util.Util;
  import java.io.ByteArrayOutputStream;
  import java.io.DataOutputStream;
  import java.io.IOException;
  
  /**
   * Encodes data that can be decoded by {@link EventMessageDecoder}. This class isn't thread safe.
   */
  public final class EventMessageEncoder {
  
    private final ByteArrayOutputStream byteArrayOutputStream;
    private final DataOutputStream dataOutputStream;
  
    public EventMessageEncoder() {
      byteArrayOutputStream = new ByteArrayOutputStream(512);
      dataOutputStream = new DataOutputStream(byteArrayOutputStream);
    }
  
    /**
     * Encodes an {@link EventMessage} to a byte array that can be decoded by
     * {@link EventMessageDecoder}.
     *
     * @param eventMessage The event message to be encoded.
     * @param timescale Timescale of the event message, in units per second.
     * @return The serialized byte array.
     */
    @Nullable
    public byte[] encode(EventMessage eventMessage, long timescale) {
      Assertions.checkArgument(timescale >= 0);
      byteArrayOutputStream.reset();
      try {
        writeNullTerminatedString(dataOutputStream, eventMessage.schemeIdUri);
        String nonNullValue = eventMessage.value != null ? eventMessage.value : "";
        writeNullTerminatedString(dataOutputStream, nonNullValue);
        writeUnsignedInt(dataOutputStream, timescale);
        long presentationTime = Util.scaleLargeTimestamp(eventMessage.presentationTimeUs,
            timescale, C.MICROS_PER_SECOND);
        writeUnsignedInt(dataOutputStream, presentationTime);
        long duration = Util.scaleLargeTimestamp(eventMessage.durationMs, timescale, 1000);
        writeUnsignedInt(dataOutputStream, duration);
        writeUnsignedInt(dataOutputStream, eventMessage.id);
        dataOutputStream.write(eventMessage.messageData);
        dataOutputStream.flush();
        return byteArrayOutputStream.toByteArray();
      } catch (IOException e) {
        // Should never happen.
        throw new RuntimeException(e);
      }
    }
  
    private static void writeNullTerminatedString(DataOutputStream dataOutputStream, String value)
        throws IOException {
      dataOutputStream.writeBytes(value);
      dataOutputStream.writeByte(0);
    }
  
    private static void writeUnsignedInt(DataOutputStream outputStream, long value)
        throws IOException {
      outputStream.writeByte((int) (value >>> 24) & 0xFF);
      outputStream.writeByte((int) (value >>> 16) & 0xFF);
      outputStream.writeByte((int) (value >>> 8) & 0xFF);
      outputStream.writeByte((int) value & 0xFF);
    }
  
  }
  