shaka-player
Version:
DASH/EME video player library
375 lines (334 loc) • 11.8 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.hls.ManifestTextParser');
goog.require('shaka.hls.Attribute');
goog.require('shaka.hls.Playlist');
goog.require('shaka.hls.PlaylistType');
goog.require('shaka.hls.Segment');
goog.require('shaka.hls.Tag');
goog.require('shaka.hls.Utils');
goog.require('shaka.util.Error');
goog.require('shaka.util.StringUtils');
/**
* HlS manifest text parser.
*/
shaka.hls.ManifestTextParser = class {
constructor() {
/** @private {number} */
this.globalId_ = 0;
}
/**
* @param {BufferSource} data
* @return {!shaka.hls.Playlist}
*/
parsePlaylist(data) {
// Get the input as a string. Normalize newlines to \n.
const str = shaka.util.StringUtils.fromUTF8(data);
const lines = str.trim().split(/[\r\n]+/);
if (!lines[0].startsWith('#EXTM3U')) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MANIFEST,
shaka.util.Error.Code.HLS_PLAYLIST_HEADER_MISSING);
}
// Single-pass state machine for parsing
let playlistType = shaka.hls.PlaylistType.MASTER;
let typeDetected = false;
const tags = [];
let skip = true;
for (let i = 0; i < lines.length; i++) {
const line = lines[i];
const next = lines[i + 1];
// Skip comments
if (shaka.hls.Utils.isComment(line) || skip) {
skip = false;
continue;
}
const tag = this.parseTag_(line);
// Detect playlist type on first relevant tag
if (!typeDetected) {
if (shaka.hls.ManifestTextParser.MEDIA_PLAYLIST_TAGS.has(tag.name)) {
playlistType = shaka.hls.PlaylistType.MEDIA;
typeDetected = true;
} else if (tag.name == 'EXT-X-STREAM-INF' ||
tag.name == 'EXT-X-MEDIA') {
// Master playlist detected, keep as MASTER
typeDetected = true;
} else if (shaka.hls.ManifestTextParser.SEGMENT_TAGS.has(tag.name)) {
// Segment tags also indicate MEDIA playlist
playlistType = shaka.hls.PlaylistType.MEDIA;
typeDetected = true;
}
}
// Transition to segment parsing
if (shaka.hls.ManifestTextParser.SEGMENT_TAGS.has(tag.name)) {
if (playlistType != shaka.hls.PlaylistType.MEDIA) {
// Only media playlists should contain segment tags
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MANIFEST,
shaka.util.Error.Code.HLS_INVALID_PLAYLIST_HIERARCHY);
}
const segments = this.parseSegments_(lines, i, tags);
return new shaka.hls.Playlist(playlistType, tags, segments);
}
tags.push(tag);
// An EXT-X-STREAM-INF tag is followed by a URI of a media playlist.
// Add the URI to the tag object.
if (tag.name == 'EXT-X-STREAM-INF') {
const tagUri = new shaka.hls.Attribute('URI', next);
tag.addAttribute(tagUri);
skip = true;
}
}
return new shaka.hls.Playlist(playlistType, tags);
}
/**
* Parses an array of strings into an array of HLS Segment objects.
*
* @param {!Array<string>} lines
* @param {number} startIndex
* @param {!Array<!shaka.hls.Tag>} playlistTags
* @return {!Array<shaka.hls.Segment>}
* @private
*/
parseSegments_(lines, startIndex, playlistTags) {
// Pre-allocate segments array for better performance with large playlists
const remainingLines = lines.length - startIndex;
const estimatedSegments = Math.max(100, Math.floor(remainingLines / 2));
/** @type {!Array<shaka.hls.Segment>} */
const segments = new Array(estimatedSegments);
let segmentIndex = 0;
/** @type {!Array<shaka.hls.Tag>} */
let segmentTags = [];
/** @type {!Array<shaka.hls.Tag>} */
let partialSegmentTags = [];
// The last parsed EXT-X-MAP tag.
/** @type {?shaka.hls.Tag} */
let currentMapTag = null;
for (let lineIndex = startIndex; lineIndex < lines.length; lineIndex++) {
const line = lines[lineIndex];
if (line.startsWith('#EXT')) {
const tag = this.parseTag_(line);
if (shaka.hls.ManifestTextParser.MEDIA_PLAYLIST_TAGS.has(tag.name)) {
playlistTags.push(tag);
} else {
// Mark the EXT-X-MAP tag, and add it to the segment tags
// following it later.
if (tag.name == 'EXT-X-MAP') {
currentMapTag = tag;
} else if (tag.name == 'EXT-X-PART') {
partialSegmentTags.push(tag);
} else if (tag.name == 'EXT-X-PRELOAD-HINT') {
if (tag.getAttributeValue('TYPE') == 'PART') {
partialSegmentTags.push(tag);
} else if (tag.getAttributeValue('TYPE') == 'MAP') {
// Rename the Preload Hint tag to be a Map tag.
tag.setName('EXT-X-MAP');
currentMapTag = tag;
}
} else {
segmentTags.push(tag);
}
}
} else if (shaka.hls.Utils.isComment(line)) {
// Skip comments.
} else {
const verbatimSegmentUri = line.trim();
// Attach the last parsed EXT-X-MAP tag to the segment.
if (currentMapTag) {
segmentTags.push(currentMapTag);
}
// The URI appears after all of the tags describing the segment.
const segment = new shaka.hls.Segment(
verbatimSegmentUri, segmentTags, partialSegmentTags);
if (segmentIndex < segments.length) {
segments[segmentIndex++] = segment;
} else {
segments.push(segment);
segmentIndex++;
}
segmentTags = [];
partialSegmentTags = [];
}
}
// After all the partial segments of a regular segment is published,
// a EXTINF tag and Uri for a regular segment containing the same media
// content will get published at last.
// If no EXTINF tag follows the list of partial segment tags at the end,
// create a segment to wrap the partial segment tags.
if (partialSegmentTags.length) {
if (currentMapTag) {
segmentTags.push(currentMapTag);
}
const segment = new shaka.hls.Segment('', segmentTags,
partialSegmentTags);
if (segmentIndex < segments.length) {
segments[segmentIndex++] = segment;
} else {
segments.push(segment);
segmentIndex++;
}
}
// Trim pre-allocated array to actual size
return segmentIndex < segments.length ?
segments.slice(0, segmentIndex) : segments;
}
/**
* Parses a string into an HLS Tag object while tracking what id to use next.
*
* @param {string} word
* @return {!shaka.hls.Tag}
* @private
*/
parseTag_(word) {
return shaka.hls.ManifestTextParser.parseTag(this.globalId_++, word);
}
/**
* Parses a string into an HLS Tag object.
*
* @param {number} id
* @param {string} word
* @return {!shaka.hls.Tag}
*/
static parseTag(id, word) {
/* HLS tags start with '#EXT'. A tag can have a set of attributes
(#EXT-<tagname>:<attribute list>) and/or a value (#EXT-<tagname>:<value>).
An attribute's format is 'AttributeName=AttributeValue'.
The parsing logic goes like this:
1. Everything before ':' is a name (we ignore '#').
2. Everything after ':' is a list of comma-separated items,
2a. The first item might be a value, if it does not contain '='.
2b. Otherwise, items are attributes.
3. If there is no ":", it's a simple tag with no attributes and no value.
*/
const {name, data} = shaka.hls.ManifestTextParser.splitTag_(word);
// No data means a simple tag: #EXT-X-ENDLIST, #EXT-X-DISCONTINUITY
if (data === null) {
return new shaka.hls.Tag(id, name, []);
}
// No '=' means value-only, no attributes.
// Covers EXTINF, EXT-X-TARGETDURATION, EXT-X-MEDIA-SEQUENCE, etc.
if (data.indexOf('=') === -1) {
return new shaka.hls.Tag(id, name, [], data);
}
// Has attributes — full parse needed
const attributes = shaka.hls.ManifestTextParser.parseAttributes_(data);
return new shaka.hls.Tag(id, name, attributes.list, attributes.value);
}
/**
* Splits a raw HLS tag string into its name and data portions.
* Validates that the tag name starts with 'EXT'.
*
* @param {string} word Raw tag line, e.g. '#EXT-X-MEDIA:TYPE=AUDIO'
* @return {{name: string, data: ?string}}
* @private
*/
static splitTag_(word) {
const colonIndex = word.indexOf(':');
const name = colonIndex === -1 ?
word.substring(1) : word.substring(1, colonIndex);
if (!name.startsWith('EXT')) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MANIFEST,
shaka.util.Error.Code.INVALID_HLS_TAG,
word);
}
const data = colonIndex === -1 ? null : word.substring(colonIndex + 1);
return {name, data};
}
/**
* Parses the data portion of an HLS tag into an optional leading value
* and a list of key=value attributes.
*
* @param {string} data
* @return {{value: ?string, list: !Array<!shaka.hls.Attribute>}}
* @private
*/
static parseAttributes_(data) {
const list = [];
let value = null;
let pos = 0;
// A leading value exists if the first comma comes before the first '='
const firstComma = data.indexOf(',');
const firstEquals = data.indexOf('=');
if (firstComma !== -1 && firstComma < firstEquals) {
value = data.substring(0, firstComma);
pos = firstComma + 1;
}
// Parse comma-separated key=value pairs
while (pos < data.length) {
// Skip optional spaces after comma (HLS spec allows it)
while (data[pos] === ' ') {
pos++;
}
const eqPos = data.indexOf('=', pos);
if (eqPos === -1) {
break;
}
const attrName = data.substring(pos, eqPos);
pos = eqPos + 1;
// Read attribute value (quoted or unquoted)
let attrValue;
if (data[pos] === '"') {
pos++;
const closeQuote = data.indexOf('"', pos);
attrValue = closeQuote === -1 ?
data.substring(pos) : data.substring(pos, closeQuote);
pos = closeQuote === -1 ? data.length : closeQuote + 1;
} else {
const commaPos = data.indexOf(',', pos);
attrValue = commaPos === -1 ?
data.substring(pos) : data.substring(pos, commaPos);
pos = commaPos === -1 ? data.length : commaPos;
}
// Skip comma separator
if (pos < data.length && data[pos] === ',') {
pos++;
}
list.push(new shaka.hls.Attribute(attrName, attrValue));
}
return {value, list};
}
};
/**
* HLS tags that only appear on Media Playlists.
* Used to determine a playlist type.
* O(1) lookup set for tag classification.
*
* @const {!Set<string>}
*/
shaka.hls.ManifestTextParser.MEDIA_PLAYLIST_TAGS = new Set([
'EXT-X-TARGETDURATION',
'EXT-X-MEDIA-SEQUENCE',
'EXT-X-DISCONTINUITY-SEQUENCE',
'EXT-X-PLAYLIST-TYPE',
'EXT-X-I-FRAMES-ONLY',
'EXT-X-ENDLIST',
'EXT-X-SERVER-CONTROL',
'EXT-X-SKIP',
'EXT-X-PART-INF',
'EXT-X-DATERANGE',
]);
/**
* HLS tags that only appear on Segments in a Media Playlists.
* Used to determine the start of the segments info.
* O(1) lookup set for tag classification.
*
* @const {!Set<string>}
*/
shaka.hls.ManifestTextParser.SEGMENT_TAGS = new Set([
'EXTINF',
'EXT-X-BYTERANGE',
'EXT-X-DISCONTINUITY',
'EXT-X-PROGRAM-DATE-TIME',
'EXT-X-KEY',
'EXT-X-DATERANGE',
'EXT-X-MAP',
'EXT-X-GAP',
'EXT-X-TILES',
]);