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/*
* Copyright (C) 2016 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 org.mozilla.thirdparty.com.google.android.exoplayer2.text.webvtt;
import android.text.TextUtils;
import org.mozilla.thirdparty.com.google.android.exoplayer2.ParserException;
import org.mozilla.thirdparty.com.google.android.exoplayer2.text.SimpleSubtitleDecoder;
import org.mozilla.thirdparty.com.google.android.exoplayer2.text.Subtitle;
import org.mozilla.thirdparty.com.google.android.exoplayer2.text.SubtitleDecoderException;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray;
import java.util.ArrayList;
import java.util.List;
/**
* A {@link SimpleSubtitleDecoder} for WebVTT.
* <p>
* @see <a href="http://dev.w3.org/html5/webvtt">WebVTT specification</a>
*/
public final class WebvttDecoder extends SimpleSubtitleDecoder {
private static final int EVENT_NONE = -1;
private static final int EVENT_END_OF_FILE = 0;
private static final int EVENT_COMMENT = 1;
private static final int EVENT_STYLE_BLOCK = 2;
private static final int EVENT_CUE = 3;
private static final String COMMENT_START = "NOTE";
private static final String STYLE_START = "STYLE";
private final WebvttCueParser cueParser;
private final ParsableByteArray parsableWebvttData;
private final WebvttCue.Builder webvttCueBuilder;
private final CssParser cssParser;
private final List<WebvttCssStyle> definedStyles;
public WebvttDecoder() {
super("WebvttDecoder");
cueParser = new WebvttCueParser();
parsableWebvttData = new ParsableByteArray();
webvttCueBuilder = new WebvttCue.Builder();
cssParser = new CssParser();
definedStyles = new ArrayList<>();
}
@Override
protected Subtitle decode(byte[] bytes, int length, boolean reset)
throws SubtitleDecoderException {
parsableWebvttData.reset(bytes, length);
// Initialization for consistent starting state.
webvttCueBuilder.reset();
definedStyles.clear();
// Validate the first line of the header, and skip the remainder.
try {
WebvttParserUtil.validateWebvttHeaderLine(parsableWebvttData);
} catch (ParserException e) {
throw new SubtitleDecoderException(e);
}
while (!TextUtils.isEmpty(parsableWebvttData.readLine())) {}
int event;
ArrayList<WebvttCue> subtitles = new ArrayList<>();
while ((event = getNextEvent(parsableWebvttData)) != EVENT_END_OF_FILE) {
if (event == EVENT_COMMENT) {
skipComment(parsableWebvttData);
} else if (event == EVENT_STYLE_BLOCK) {
if (!subtitles.isEmpty()) {
throw new SubtitleDecoderException("A style block was found after the first cue.");
}
parsableWebvttData.readLine(); // Consume the "STYLE" header.
definedStyles.addAll(cssParser.parseBlock(parsableWebvttData));
} else if (event == EVENT_CUE) {
if (cueParser.parseCue(parsableWebvttData, webvttCueBuilder, definedStyles)) {
subtitles.add(webvttCueBuilder.build());
webvttCueBuilder.reset();
}
}
}
return new WebvttSubtitle(subtitles);
}
/**
* Positions the input right before the next event, and returns the kind of event found. Does not
* consume any data from such event, if any.
*
* @return The kind of event found.
*/
private static int getNextEvent(ParsableByteArray parsableWebvttData) {
int foundEvent = EVENT_NONE;
int currentInputPosition = 0;
while (foundEvent == EVENT_NONE) {
currentInputPosition = parsableWebvttData.getPosition();
String line = parsableWebvttData.readLine();
if (line == null) {
foundEvent = EVENT_END_OF_FILE;
} else if (STYLE_START.equals(line)) {
foundEvent = EVENT_STYLE_BLOCK;
} else if (line.startsWith(COMMENT_START)) {
foundEvent = EVENT_COMMENT;
} else {
foundEvent = EVENT_CUE;
}
}
parsableWebvttData.setPosition(currentInputPosition);
return foundEvent;
}
private static void skipComment(ParsableByteArray parsableWebvttData) {
while (!TextUtils.isEmpty(parsableWebvttData.readLine())) {}
}
}
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