Add file missing from "Improve subtitle handling" change.

library/src/main/java/com/google/android/exoplayer/text/SubtitleParserHelper.java

+/*
+ * Copyright (C) 2014 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.exoplayer.text;
+
+import com.google.android.exoplayer.SampleHolder;
+import com.google.android.exoplayer.util.Assertions;
+
+import android.media.MediaCodec;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Wraps a {@link SubtitleParser}, exposing an interface similar to {@link MediaCodec} for
+ * asynchronous parsing of subtitles.
+ */
+public class SubtitleParserHelper implements Handler.Callback {
+
+  private final SubtitleParser parser;
+
+  private final Handler handler;
+  private SampleHolder sampleHolder;
+  private boolean parsing;
+  private Subtitle result;
+  private IOException error;
+
+  /**
+   * @param looper The {@link Looper} associated with the thread on which parsing should occur.
+   * @param parser The parser that should be used to parse the raw data.
+   */
+  public SubtitleParserHelper(Looper looper, SubtitleParser parser) {
+    this.handler = new Handler(looper, this);
+    this.parser = parser;
+    flush();
+  }
+
+  /**
+   * Flushes the helper, canceling the current parsing operation, if there is one.
+   */
+  public synchronized void flush() {
+    sampleHolder = new SampleHolder(true);
+    parsing = false;
+    result = null;
+    error = null;
+  }
+
+  /**
+   * Whether the helper is currently performing a parsing operation.
+   *
+   * @return True if the helper is currently performing a parsing operation. False otherwise.
+   */
+  public synchronized boolean isParsing() {
+    return parsing;
+  }
+
+  /**
+   * Gets the holder that should be populated with data to be parsed.
+   * <p>
+   * The returned holder will remain valid unless {@link #flush()} is called. If {@link #flush()}
+   * is called the holder is replaced, and this method should be called again to obtain the new
+   * holder.
+   *
+   * @return The holder that should be populated with data to be parsed.
+   */
+  public synchronized SampleHolder getSampleHolder() {
+    return sampleHolder;
+  }
+
+  /**
+   * Start a parsing operation.
+   * <p>
+   * The holder returned by {@link #getSampleHolder()} should be populated with the data to be
+   * parsed prior to calling this method.
+   */
+  public synchronized void startParseOperation() {
+    Assertions.checkState(!parsing);
+    parsing = true;
+    result = null;
+    error = null;
+    handler.obtainMessage(0, sampleHolder).sendToTarget();
+  }
+
+  /**
+   * Gets the result of the most recent parsing operation.
+   * <p>
+   * The result is cleared as a result of calling this method, and so subsequent calls will return
+   * null until a subsequent parsing operation has finished.
+   *
+   * @return The result of the parsing operation, or null.
+   * @throws IOException If the parsing operation failed.
+   */
+  public synchronized Subtitle getAndClearResult() throws IOException {
+    try {
+      if (error != null) {
+        throw error;
+      }
+      return result;
+    } finally {
+      error = null;
+      result = null;
+    }
+  }
+
+  @Override
+  public boolean handleMessage(Message msg) {
+    Subtitle result;
+    IOException error;
+    SampleHolder holder = (SampleHolder) msg.obj;
+    try {
+      InputStream inputStream = new ByteArrayInputStream(holder.data.array(), 0, holder.size);
+      result = parser.parse(inputStream, null, sampleHolder.timeUs);
+      error = null;
+    } catch (IOException e) {
+      result = null;
+      error = e;
+    }
+    synchronized (this) {
+      if (sampleHolder != holder) {
+        // A flush has occurred since this holder was posted. Do nothing.
+      } else {
+        holder.data.position(0);
+        this.result = result;
+        this.error = error;
+        this.parsing = false;
+      }
+    }
+    return true;
+  }
+
+}