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Make Parser Async #373

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Make Parser Async #373

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e950ce9
Make Parser Async
Jun 17, 2018
77a83c1
Don't check for `self.vttjs.VTTCue`
Jun 18, 2018
e4f5f56
Update vtt.js
jaruba Aug 24, 2021
84d33d1
Fix Warning About Invalid `cue.positionAlign` Value
jaruba Mar 1, 2024
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241 changes: 167 additions & 74 deletions lib/vtt.js
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Original file line number Diff line number Diff line change
Expand Up @@ -204,15 +204,18 @@
}
}

function parseCue(input, cue, regionList) {
function parseCue(input, cue, regionList, successCb, errCb) {
// Remember the original input if we need to throw an error.
var oInput = input;
// 4.1 WebVTT timestamp
function consumeTimeStamp() {
var ts = parseTimeStamp(input);
if (ts === null) {
throw new ParsingError(ParsingError.Errors.BadTimeStamp,
"Malformed timestamp: " + oInput);
if (errCb) {
errCb(new ParsingError(ParsingError.Errors.BadTimeStamp,
"Malformed timestamp: " + oInput));
return;
}
}
// Remove time stamp from input.
input = input.replace(/^[^\sa-zA-Z-]+/, "");
Expand Down Expand Up @@ -270,15 +273,18 @@
cue.lineAlign = settings.get("lineAlign", "start");
cue.snapToLines = settings.get("snapToLines", true);
cue.size = settings.get("size", 100);
cue.align = settings.get("align", "middle");
cue.align = settings.get("align", "center");
cue.position = settings.get("position", "auto");
cue.positionAlign = settings.get("positionAlign", {
start: "start",
left: "start",
middle: "middle",
end: "end",
right: "end"
right: "end",
center: "center"
}, cue.align);

successCb();
}

function skipWhitespace() {
Expand All @@ -287,16 +293,23 @@

// 4.1 WebVTT cue timings.
skipWhitespace();
cue.startTime = consumeTimeStamp(); // (1) collect cue start time

var timestamp = consumeTimeStamp()
if (timestamp === undefined) return
cue.startTime = timestamp; // (1) collect cue start time
skipWhitespace();
if (input.substr(0, 3) !== "-->") { // (3) next characters must match "-->"
throw new ParsingError(ParsingError.Errors.BadTimeStamp,
if (input.substr(0, 3) !== "-->") {
// (3) next characters must match "-->"
errCb(new ParsingError(ParsingError.Errors.BadTimeStamp,
"Malformed time stamp (time stamps must be separated by '-->'): " +
oInput);
oInput));
return;
}
input = input.substr(3);
skipWhitespace();
cue.endTime = consumeTimeStamp(); // (5) collect cue end time
var timestamp = consumeTimeStamp()
if (timestamp === undefined) return
cue.endTime = timestamp; // (5) collect cue end time

// 4.1 WebVTT cue settings list.
skipWhitespace();
Expand Down Expand Up @@ -1076,12 +1089,13 @@
})();
};

WebVTT.Parser = function(window, decoder) {
WebVTT.Parser = function(window, decoder, VTTCue) {
this.window = window;
this.state = "INITIAL";
this.buffer = "";
this.decoder = decoder || new TextDecoder("utf8");
this.regionList = [];
this.VTTCue = VTTCue
};

WebVTT.Parser.prototype = {
Expand Down Expand Up @@ -1183,51 +1197,104 @@
}
}

// 3.2 WebVTT metadata header syntax
function parseHeader(input) {
parseOptions(input, function (k, v) {
// draft-pantos-http-live-streaming-20
// https://tools.ietf.org/html/draft-pantos-http-live-streaming-20#section-3.5
// 3.5 WebVTT
function parseTimestampMap(input) {
var settings = new Settings();

parseOptions(input, function(k, v) {
switch (k) {
case "Region":
// 3.3 WebVTT region metadata header syntax
parseRegion(v);
break;
case "MPEGT":
settings.integer(k + 'S', v);
break;
case "LOCA":
settings.set(k + 'L', parseTimeStamp(v));
break;
}
}, /:/);
}, /[^\d]:/, /,/);

self.ontimestampmap && self.ontimestampmap({
"MPEGTS": settings.get("MPEGTS"),
"LOCAL": settings.get("LOCAL")
});
}

// 3.2 WebVTT metadata header syntax
function parseHeader(input) {
if (input.match(/X-TIMESTAMP-MAP/)) {
// This line contains HLS X-TIMESTAMP-MAP metadata
parseOptions(input, function(k, v) {
switch (k) {
case "X-TIMESTAMP-MAP":
parseTimestampMap(v);
break;
}
}, /=/);
} else {
parseOptions(input, function (k, v) {
switch (k) {
case "Region":
// 3.3 WebVTT region metadata header syntax
parseRegion(v);
break;
}
}, /:/);
}
}

// 5.1 WebVTT file parsing.
try {
var line;
if (self.state === "INITIAL") {
// We can't start parsing until we have the first line.
if (!/\r\n|\n/.test(self.buffer)) {
return this;
}

line = collectNextLine();
function fail(e) {

var m = line.match(/^WEBVTT([ \t].*)?$/);
if (!m || !m[0]) {
throw new ParsingError(ParsingError.Errors.BadSignature);
}
self.reportOrThrowError(e);

self.state = "HEADER";
// If we are currently parsing a cue, report what we have.
if (self.state === "CUETEXT" && self.cue && self.oncue) {
self.oncue(self.cue);
}
self.cue = null;
// Enter BADWEBVTT state if header was not parsed correctly otherwise
// another exception occurred so enter BADCUE state.
self.state = self.state === "INITIAL" ? "BADWEBVTT" : "BADCUE";

var alreadyCollectedLine = false;
while (self.buffer) {
// We can't parse a line until we have the full line.
if (!/\r\n|\n/.test(self.buffer)) {
return this;
}
}

if (!alreadyCollectedLine) {
line = collectNextLine();
} else {
alreadyCollectedLine = false;
}
var line;

if (self.state === "INITIAL") {
// We can't start parsing until we have the first line.
if (!/\r\n|\n/.test(self.buffer)) {
return this;
}

line = collectNextLine();

var m = line.match(/^WEBVTT([ \t].*)?$/);
if (!m || !m[0]) {
fail(new ParsingError(ParsingError.Errors.BadSignature))
return
}

switch (self.state) {
self.state = "HEADER";
}

var alreadyCollectedLine = false;

var lineparse = function() {
// We can't parse a line until we have the full line.
if (!self.buffer || !/\r\n|\n/.test(self.buffer)) {
self.flush()
return
}

if (!alreadyCollectedLine) {
line = collectNextLine();
} else {
alreadyCollectedLine = false;
}

switch (self.state) {
case "HEADER":
// 13-18 - Allow a header (metadata) under the WEBVTT line.
if (/:/.test(line)) {
Expand All @@ -1236,45 +1303,59 @@
// An empty line terminates the header and starts the body (cues).
self.state = "ID";
}
continue;
linebyline();
break;
case "NOTE":
// Ignore NOTE blocks.
if (!line) {
self.state = "ID";
}
continue;
linebyline();
break;
case "ID":
// Check for the start of NOTE blocks.
if (/^NOTE($|[ \t])/.test(line)) {
self.state = "NOTE";
linebyline();
break;
}
// 19-29 - Allow any number of line terminators, then initialize new cue values.
if (!line) {
continue;
linebyline();
break;
}
self.cue = new self.window.VTTCue(0, 0, "");
self.cue = new (self.VTTCue || self.window.VTTCue)(0, 0, "");
self.state = "CUE";
// 30-39 - Check if self line contains an optional identifier or timing data.
if (line.indexOf("-->") === -1) {
self.cue.id = line;
continue;
linebyline();
break;
}
// Process line as start of a cue.
/*falls through*/
// Process line as start of a cue.
/*falls through*/
case "CUE":
// 40 - Collect cue timings and settings.
try {
parseCue(line, self.cue, self.regionList);
} catch (e) {
self.reportOrThrowError(e);

parseCue(line, self.cue, self.regionList, function successCb() {

self.state = "CUETEXT";

linebyline();

}, function errCb(err) {

self.reportOrThrowError(err);

// In case of an error ignore rest of the cue.
self.cue = null;
self.state = "BADCUE";
continue;
}
self.state = "CUETEXT";
continue;

linebyline();

});

break;
case "CUETEXT":
var hasSubstring = line.indexOf("-->") !== -1;
// 34 - If we have an empty line then report the cue.
Expand All @@ -1286,33 +1367,45 @@
self.oncue && self.oncue(self.cue);
self.cue = null;
self.state = "ID";
continue;
}
linebyline();
break;
}
if (self.cue.text) {
self.cue.text += "\n";
}
self.cue.text += line;
continue;
case "BADCUE": // BADCUE
linebyline();
break;
case "BADCUE":
// BADCUE
// 54-62 - Collect and discard the remaining cue.
if (!line) {
self.state = "ID";
}
continue;
}
linebyline();
break;
}
} catch (e) {
self.reportOrThrowError(e);
};

// If we are currently parsing a cue, report what we have.
if (self.state === "CUETEXT" && self.cue && self.oncue) {
self.oncue(self.cue);
var STACK_LIMIT = 1000;

var count = 0

function unwrapStack(fn) {
return function() {
count++
if (count < STACK_LIMIT) return fn()
setTimeout(function() {
count = 0
fn()
})
}
self.cue = null;
// Enter BADWEBVTT state if header was not parsed correctly otherwise
// another exception occurred so enter BADCUE state.
self.state = self.state === "INITIAL" ? "BADWEBVTT" : "BADCUE";
}

var linebyline = unwrapStack(lineparse)

linebyline();

return this;
},
flush: function () {
Expand Down