shaka-player
Version:
DASH/EME video player library
346 lines (311 loc) • 11.1 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');
goog.require('shaka.util.TextParser');
/**
* 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.
let str = shaka.util.StringUtils.fromUTF8(data);
str = str.replace(/\r\n|\r(?=[^\n]|$)/gm, '\n').trim();
const lines = str.split(/\n+/m);
if (!shaka.hls.ManifestTextParser.STATIC_PATTERNS.header.test(lines[0])) {
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 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 blocks = word.match(
shaka.hls.ManifestTextParser.STATIC_PATTERNS.tagBlocks);
if (!blocks) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MANIFEST,
shaka.util.Error.Code.INVALID_HLS_TAG,
word);
}
const name = blocks[1];
const data = blocks[2];
const attributes = [];
let value;
if (data) {
const parser = new shaka.util.TextParser(data);
let blockAttrs;
// re-using global regex: reset lastIndex
shaka.hls.ManifestTextParser.STATIC_PATTERNS.valueRegex.lastIndex = 0;
const blockValue = parser.readRegex(
shaka.hls.ManifestTextParser.STATIC_PATTERNS.valueRegex);
if (blockValue) {
value = blockValue[1];
}
// re-using global regex: reset lastIndex
shaka.hls.ManifestTextParser.STATIC_PATTERNS.attributeRegex.lastIndex = 0;
blockAttrs = parser.readRegex(
shaka.hls.ManifestTextParser.STATIC_PATTERNS.attributeRegex);
while (blockAttrs) {
const attrName = blockAttrs[1];
const attrValue = blockAttrs[2] || blockAttrs[3];
const attribute = new shaka.hls.Attribute(attrName, attrValue);
attributes.push(attribute);
parser.skipWhitespace();
blockAttrs = parser.readRegex(
shaka.hls.ManifestTextParser.STATIC_PATTERNS.attributeRegex);
}
}
return new shaka.hls.Tag(id, name, attributes, value);
}
};
/**
* Static pre-compiled regex patterns for maximum performance.
* Shared across all parser instances.
* Pre-compiled patterns eliminate repeated regex compilation during parsing.
* @const {{tagBlocks: !RegExp, valueRegex: !RegExp, attributeRegex: !RegExp,
* header: !RegExp}}
*/
shaka.hls.ManifestTextParser.STATIC_PATTERNS = {
tagBlocks: /^#(EXT[^:]*)(?::(.*))?$/,
header: /^#EXTM3U($|[ \t\n])/m,
// Regex: any number of non-equals-sign characters at the beginning
// terminated by comma or end of line
valueRegex: /^([^,=]+)(?:,|$)/g,
// Regex:
// 1. Key name ([1])
// 2. Equals sign
// 3. Either:
// a. A quoted string (everything up to the next quote, [2])
// b. An unquoted string
// (everything up to the next comma or end of line, [3])
// 4. Either:
// a. A comma
// b. End of line
attributeRegex: /([^=]+)=(?:"([^"]*)"|([^",]*))(?:,|$)/g,
};
/**
* 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',
]);