shaka-player
Version:
DASH/EME video player library
457 lines (394 loc) • 13.8 kB
JavaScript
/*! @license
* Shaka Player
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.util.XmlUtils');
goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.util.Lazy');
goog.require('shaka.util.StringUtils');
/**
* @summary A set of XML utility functions.
*/
shaka.util.XmlUtils = class {
/**
* Finds a child XML element.
* @param {!Node} elem The parent XML element.
* @param {string} name The child XML element's tag name.
* @return {Element} The child XML element, or null if a child XML element
* does not exist with the given tag name OR if there exists more than one
* child XML element with the given tag name.
*/
static findChild(elem, name) {
const children = shaka.util.XmlUtils.findChildren(elem, name);
if (children.length != 1) {
return null;
}
return children[0];
}
/**
* Finds a namespace-qualified child XML element.
* @param {!Node} elem The parent XML element.
* @param {string} ns The child XML element's namespace URI.
* @param {string} name The child XML element's local name.
* @return {Element} The child XML element, or null if a child XML element
* does not exist with the given tag name OR if there exists more than one
* child XML element with the given tag name.
*/
static findChildNS(elem, ns, name) {
const children = shaka.util.XmlUtils.findChildrenNS(elem, ns, name);
if (children.length != 1) {
return null;
}
return children[0];
}
/**
* Finds child XML elements.
* @param {!Node} elem The parent XML element.
* @param {string} name The child XML element's tag name.
* @return {!Array.<!Element>} The child XML elements.
*/
static findChildren(elem, name) {
const found = [];
for (const child of elem.childNodes) {
if (child instanceof Element && child.tagName == name) {
found.push(child);
}
}
return found;
}
/**
* @param {!Node} elem the parent XML element.
* @return {!Array.<!Element>} The child XML elements.
*/
static getChildren(elem) {
return Array.from(elem.childNodes).filter((child) => {
return child instanceof Element;
});
}
/**
* Finds namespace-qualified child XML elements.
* @param {!Node} elem The parent XML element.
* @param {string} ns The child XML element's namespace URI.
* @param {string} name The child XML element's local name.
* @return {!Array.<!Element>} The child XML elements.
*/
static findChildrenNS(elem, ns, name) {
const found = [];
for (const child of elem.childNodes) {
if (child instanceof Element && child.localName == name &&
child.namespaceURI == ns) {
found.push(child);
}
}
return found;
}
/**
* Gets a namespace-qualified attribute.
* @param {!Element} elem The element to get from.
* @param {string} ns The namespace URI.
* @param {string} name The local name of the attribute.
* @return {?string} The attribute's value, or null if not present.
*/
static getAttributeNS(elem, ns, name) {
// Some browsers return the empty string when the attribute is missing,
// so check if it exists first. See: https://mzl.la/2L7F0UK
return elem.hasAttributeNS(ns, name) ? elem.getAttributeNS(ns, name) : null;
}
/**
* Gets a namespace-qualified attribute.
* @param {!Element} elem The element to get from.
* @param {!Array.<string>} nsList The lis of namespace URIs.
* @param {string} name The local name of the attribute.
* @return {?string} The attribute's value, or null if not present.
*/
static getAttributeNSList(elem, nsList, name) {
// Some browsers return the empty string when the attribute is missing,
// so check if it exists first. See: https://mzl.la/2L7F0UK
for (const ns of nsList) {
if (elem.hasAttributeNS(ns, name)) {
return elem.getAttributeNS(ns, name);
}
}
return null;
}
/**
* Gets the text contents of a node.
* @param {!Node} elem The XML element.
* @return {?string} The text contents, or null if there are none.
*/
static getContents(elem) {
const XmlUtils = shaka.util.XmlUtils;
if (!Array.from(elem.childNodes).every(XmlUtils.isText)) {
return null;
}
// Read merged text content from all text nodes.
return elem.textContent.trim();
}
/**
* Checks if a node is of type text.
* @param {!Node} elem The XML element.
* @return {boolean} True if it is a text node.
*/
static isText(elem) {
return elem.nodeType == Node.TEXT_NODE ||
elem.nodeType == Node.CDATA_SECTION_NODE;
}
/**
* Parses an attribute by its name.
* @param {!Element} elem The XML element.
* @param {string} name The attribute name.
* @param {function(string): (T|null)} parseFunction A function that parses
* the attribute.
* @param {(T|null)=} defaultValue The attribute's default value, if not
* specified, the attibute's default value is null.
* @return {(T|null)} The parsed attribute on success, or the attribute's
* default value if the attribute does not exist or could not be parsed.
* @template T
*/
static parseAttr(
elem, name, parseFunction, defaultValue = null) {
let parsedValue = null;
const value = elem.getAttribute(name);
if (value != null) {
parsedValue = parseFunction(value);
}
return parsedValue == null ? defaultValue : parsedValue;
}
/**
* Parses an XML date string.
* @param {string} dateString
* @return {?number} The parsed date in seconds on success; otherwise, return
* null.
*/
static parseDate(dateString) {
if (!dateString) {
return null;
}
// Times in the manifest should be in UTC. If they don't specify a timezone,
// Date.parse() will use the local timezone instead of UTC. So manually add
// the timezone if missing ('Z' indicates the UTC timezone).
// Format: YYYY-MM-DDThh:mm:ss.ssssss
if (/^\d+-\d+-\d+T\d+:\d+:\d+(\.\d+)?$/.test(dateString)) {
dateString += 'Z';
}
const result = Date.parse(dateString);
return isNaN(result) ? null : (result / 1000.0);
}
/**
* Parses an XML duration string.
* Negative values are not supported. Years and months are treated as exactly
* 365 and 30 days respectively.
* @param {string} durationString The duration string, e.g., "PT1H3M43.2S",
* which means 1 hour, 3 minutes, and 43.2 seconds.
* @return {?number} The parsed duration in seconds on success; otherwise,
* return null.
* @see {@link http://www.datypic.com/sc/xsd/t-xsd_duration.html}
*/
static parseDuration(durationString) {
if (!durationString) {
return null;
}
const re = '^P(?:([0-9]*)Y)?(?:([0-9]*)M)?(?:([0-9]*)D)?' +
'(?:T(?:([0-9]*)H)?(?:([0-9]*)M)?(?:([0-9.]*)S)?)?$';
const matches = new RegExp(re).exec(durationString);
if (!matches) {
shaka.log.warning('Invalid duration string:', durationString);
return null;
}
// Note: Number(null) == 0 but Number(undefined) == NaN.
const years = Number(matches[1] || null);
const months = Number(matches[2] || null);
const days = Number(matches[3] || null);
const hours = Number(matches[4] || null);
const minutes = Number(matches[5] || null);
const seconds = Number(matches[6] || null);
// Assume a year always has 365 days and a month always has 30 days.
const d = (60 * 60 * 24 * 365) * years +
(60 * 60 * 24 * 30) * months +
(60 * 60 * 24) * days +
(60 * 60) * hours +
60 * minutes +
seconds;
return isFinite(d) ? d : null;
}
/**
* Parses a range string.
* @param {string} rangeString The range string, e.g., "101-9213".
* @return {?{start: number, end: number}} The parsed range on success;
* otherwise, return null.
*/
static parseRange(rangeString) {
const matches = /([0-9]+)-([0-9]+)/.exec(rangeString);
if (!matches) {
return null;
}
const start = Number(matches[1]);
if (!isFinite(start)) {
return null;
}
const end = Number(matches[2]);
if (!isFinite(end)) {
return null;
}
return {start: start, end: end};
}
/**
* Parses an integer.
* @param {string} intString The integer string.
* @return {?number} The parsed integer on success; otherwise, return null.
*/
static parseInt(intString) {
const n = Number(intString);
return (n % 1 === 0) ? n : null;
}
/**
* Parses a positive integer.
* @param {string} intString The integer string.
* @return {?number} The parsed positive integer on success; otherwise,
* return null.
*/
static parsePositiveInt(intString) {
const n = Number(intString);
return (n % 1 === 0) && (n > 0) ? n : null;
}
/**
* Parses a non-negative integer.
* @param {string} intString The integer string.
* @return {?number} The parsed non-negative integer on success; otherwise,
* return null.
*/
static parseNonNegativeInt(intString) {
const n = Number(intString);
return (n % 1 === 0) && (n >= 0) ? n : null;
}
/**
* Parses a floating point number.
* @param {string} floatString The floating point number string.
* @return {?number} The parsed floating point number on success; otherwise,
* return null. May return -Infinity or Infinity.
*/
static parseFloat(floatString) {
const n = Number(floatString);
return !isNaN(n) ? n : null;
}
/**
* Parses a boolean.
* @param {string} booleanString The boolean string.
* @return {boolean} The boolean
*/
static parseBoolean(booleanString) {
if (!booleanString) {
return false;
}
return booleanString.toLowerCase() === 'true';
}
/**
* Evaluate a division expressed as a string.
* @param {string} exprString
* The expression to evaluate, e.g. "200/2". Can also be a single number.
* @return {?number} The evaluated expression as floating point number on
* success; otherwise return null.
*/
static evalDivision(exprString) {
let res;
let n;
if ((res = exprString.match(/^(\d+)\/(\d+)$/))) {
n = Number(res[1]) / Number(res[2]);
} else {
n = Number(exprString);
}
return !isNaN(n) ? n : null;
}
/**
* Parse a string and return the resulting root element if it was valid XML.
*
* @param {string} xmlString
* @param {string} expectedRootElemName
* @return {Element}
*/
static parseXmlString(xmlString, expectedRootElemName) {
const parser = new DOMParser();
const unsafeXmlString =
shaka.util.XmlUtils.trustedHTMLFromString_.value()(xmlString);
let unsafeXml = null;
try {
unsafeXml = parser.parseFromString(unsafeXmlString, 'text/xml');
} catch (exception) {
shaka.log.error('XML parsing exception:', exception);
return null;
}
// According to MDN, parseFromString never returns null.
goog.asserts.assert(unsafeXml, 'Parsed XML document cannot be null!');
// Check for empty documents.
const rootElem = unsafeXml.documentElement;
if (!rootElem) {
shaka.log.error('XML document was empty!');
return null;
}
// Check for parser errors.
const parserErrorElements = rootElem.getElementsByTagName('parsererror');
if (parserErrorElements.length) {
shaka.log.error('XML parser error found:', parserErrorElements[0]);
return null;
}
// The top-level element in the loaded XML should have the name we expect.
if (rootElem.tagName != expectedRootElemName) {
shaka.log.error(
`XML tag name does not match expected "${expectedRootElemName}":`,
rootElem.tagName);
return null;
}
// SECURITY: Verify that the document does not contain elements from the
// HTML or SVG namespaces, which could trigger script execution and XSS.
const iterator = document.createNodeIterator(
unsafeXml,
NodeFilter.SHOW_ALL,
);
let currentNode;
while (currentNode = iterator.nextNode()) {
if (currentNode instanceof HTMLElement ||
currentNode instanceof SVGElement) {
shaka.log.error('XML document embeds unsafe content!');
return null;
}
}
return rootElem;
}
/**
* Parse some data (auto-detecting the encoding) and return the resulting
* root element if it was valid XML.
* @param {BufferSource} data
* @param {string} expectedRootElemName
* @return {Element}
*/
static parseXml(data, expectedRootElemName) {
try {
const string = shaka.util.StringUtils.fromBytesAutoDetect(data);
return shaka.util.XmlUtils.parseXmlString(string, expectedRootElemName);
} catch (exception) {
shaka.log.error('parseXmlString threw!', exception);
return null;
}
}
};
/**
* Promote a string to TrustedHTML. This function is security-sensitive and
* should only be used with security approval where the string is guaranteed not
* to cause an XSS vulnerability.
*
* @private {!shaka.util.Lazy.<function(!string): (!TrustedHTML|!string)>}
*/
shaka.util.XmlUtils.trustedHTMLFromString_ = new shaka.util.Lazy(() => {
if (typeof trustedTypes !== 'undefined') {
// Create a Trusted Types policy for promoting the string to TrustedHTML.
// The Lazy wrapper ensures this policy is only created once.
const policy = trustedTypes.createPolicy('shaka-player#xml', {
createHTML: (s) => s,
});
return (s) => policy.createHTML(s);
}
// Fall back to strings in environments that don't support Trusted Types.
return (s) => s;
});