shaka-player
Version:
DASH/EME video player library
325 lines (270 loc) • 9.42 kB
JavaScript
/**
* @license
* Copyright 2016 Google Inc.
*
* 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.
*/
goog.provide('shaka.util.EbmlElement');
goog.provide('shaka.util.EbmlParser');
goog.require('shaka.util.DataViewReader');
goog.require('shaka.util.Error');
goog.require('shaka.util.Uint8ArrayUtils');
/**
* Creates an Extensible Binary Markup Language (EBML) parser.
* @param {!DataView} dataView The EBML data.
* @constructor
* @struct
*/
shaka.util.EbmlParser = function(dataView) {
/** @private {!DataView} */
this.dataView_ = dataView;
/** @private {!shaka.util.DataViewReader} */
this.reader_ = new shaka.util.DataViewReader(
dataView,
shaka.util.DataViewReader.Endianness.BIG_ENDIAN);
// If not already constructed, build a list of EBML dynamic size constants.
// This is not done at load-time to avoid exceptions on unsupported browsers.
if (!shaka.util.EbmlParser.DYNAMIC_SIZES) {
shaka.util.EbmlParser.DYNAMIC_SIZES = [
new Uint8Array([0xff]),
new Uint8Array([0x7f, 0xff]),
new Uint8Array([0x3f, 0xff, 0xff]),
new Uint8Array([0x1f, 0xff, 0xff, 0xff]),
new Uint8Array([0x0f, 0xff, 0xff, 0xff, 0xff]),
new Uint8Array([0x07, 0xff, 0xff, 0xff, 0xff, 0xff]),
new Uint8Array([0x03, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff]),
new Uint8Array([0x01, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff]),
];
}
};
/** @const {!Array.<!Uint8Array>} */
shaka.util.EbmlParser.DYNAMIC_SIZES;
/**
* @return {boolean} True if the parser has more data, false otherwise.
*/
shaka.util.EbmlParser.prototype.hasMoreData = function() {
return this.reader_.hasMoreData();
};
/**
* Parses an EBML element from the parser's current position, and advances
* the parser.
* @return {!shaka.util.EbmlElement} The EBML element.
* @throws {shaka.util.Error}
* @see http://matroska.org/technical/specs/rfc/index.html
*/
shaka.util.EbmlParser.prototype.parseElement = function() {
let id = this.parseId_();
// Parse the element's size.
let vint = this.parseVint_();
let size;
if (shaka.util.EbmlParser.isDynamicSizeValue_(vint)) {
// If this has an unknown size, assume that it takes up the rest of the
// data.
size = this.dataView_.byteLength - this.reader_.getPosition();
} else {
size = shaka.util.EbmlParser.getVintValue_(vint);
}
// Note that if the element's size is larger than the buffer then we are
// parsing a "partial element". This may occur if for example we are
// parsing the beginning of some WebM container data, but our buffer does
// not contain the entire WebM container data.
let elementSize =
this.reader_.getPosition() + size <= this.dataView_.byteLength ?
size :
this.dataView_.byteLength - this.reader_.getPosition();
let dataView = new DataView(
this.dataView_.buffer,
this.dataView_.byteOffset + this.reader_.getPosition(), elementSize);
this.reader_.skip(elementSize);
return new shaka.util.EbmlElement(id, dataView);
};
/**
* Parses an EBML ID from the parser's current position, and advances the
* parser.
* @throws {shaka.util.Error}
* @return {number} The EBML ID.
* @private
*/
shaka.util.EbmlParser.prototype.parseId_ = function() {
let vint = this.parseVint_();
if (vint.length > 7) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.EBML_OVERFLOW);
}
let id = 0;
for (let i = 0; i < vint.length; i++) {
// Note that we cannot use << since |value| may exceed 32 bits.
id = (256 * id) + vint[i];
}
return id;
};
/**
* Parses a variable sized integer from the parser's current position, and
* advances the parser.
* For example:
* 1 byte wide: 1xxx xxxx
* 2 bytes wide: 01xx xxxx xxxx xxxx
* 3 bytes wide: 001x xxxx xxxx xxxx xxxx xxxx
* @throws {shaka.util.Error}
* @return {!Uint8Array} The variable sized integer.
* @private
*/
shaka.util.EbmlParser.prototype.parseVint_ = function() {
let firstByte = this.reader_.readUint8();
let numBytes;
// Determine the byte width of the variable sized integer.
for (numBytes = 1; numBytes <= 8; numBytes++) {
let mask = 0x1 << (8 - numBytes);
if (firstByte & mask) {
break;
}
}
if (numBytes > 8) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.EBML_OVERFLOW);
}
let vint = new Uint8Array(numBytes);
vint[0] = firstByte;
// Include the remaining bytes.
for (let i = 1; i < numBytes; i++) {
vint[i] = this.reader_.readUint8();
}
return vint;
};
/**
* Gets the value of a variable sized integer.
* For example, the x's below are part of the vint's value.
* 7-bit value: 1xxx xxxx
* 14-bit value: 01xx xxxx xxxx xxxx
* 21-bit value: 001x xxxx xxxx xxxx xxxx xxxx
* @param {!Uint8Array} vint The variable sized integer.
* @throws {shaka.util.Error}
* @return {number} The value of the variable sized integer.
* @private
*/
shaka.util.EbmlParser.getVintValue_ = function(vint) {
// If |vint| is 8 bytes wide then we must ensure that it does not have more
// than 53 meaningful bits. For example, assume |vint| is 8 bytes wide,
// so it has the following structure,
// 0000 0001 | xxxx xxxx ...
// Thus, the first 3 bits following the first byte of |vint| must be 0.
if ((vint.length == 8) && (vint[1] & 0xe0)) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.JS_INTEGER_OVERFLOW);
}
// Mask out the first few bits of |vint|'s first byte to get the most
// significant bits of |vint|'s value. If |vint| is 8 bytes wide then |value|
// will be set to 0.
let mask = 0x1 << (8 - vint.length);
let value = vint[0] & (mask - 1);
// Add the remaining bytes.
for (let i = 1; i < vint.length; i++) {
// Note that we cannot use << since |value| may exceed 32 bits.
value = (256 * value) + vint[i];
}
return value;
};
/**
* Checks if the given variable sized integer represents a dynamic size value.
* @param {!Uint8Array} vint The variable sized integer.
* @return {boolean} true if |vint| represents a dynamic size value,
* false otherwise.
* @private
*/
shaka.util.EbmlParser.isDynamicSizeValue_ = function(vint) {
const EbmlParser = shaka.util.EbmlParser;
let uint8ArrayEqual = shaka.util.Uint8ArrayUtils.equal;
for (let i = 0; i < EbmlParser.DYNAMIC_SIZES.length; i++) {
if (uint8ArrayEqual(vint, EbmlParser.DYNAMIC_SIZES[i])) {
return true;
}
}
return false;
};
/**
* Creates an EbmlElement.
* @param {number} id The ID.
* @param {!DataView} dataView The DataView.
* @constructor
*/
shaka.util.EbmlElement = function(id, dataView) {
/** @type {number} */
this.id = id;
/** @private {!DataView} */
this.dataView_ = dataView;
};
/**
* Gets the element's offset from the beginning of the buffer.
* @return {number}
*/
shaka.util.EbmlElement.prototype.getOffset = function() {
return this.dataView_.byteOffset;
};
/**
* Interpret the element's data as a list of sub-elements.
* @throws {shaka.util.Error}
* @return {!shaka.util.EbmlParser} A parser over the sub-elements.
*/
shaka.util.EbmlElement.prototype.createParser = function() {
return new shaka.util.EbmlParser(this.dataView_);
};
/**
* Interpret the element's data as an unsigned integer.
* @throws {shaka.util.Error}
* @return {number}
*/
shaka.util.EbmlElement.prototype.getUint = function() {
if (this.dataView_.byteLength > 8) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.EBML_OVERFLOW);
}
// Ensure we have at most 53 meaningful bits.
if ((this.dataView_.byteLength == 8) && (this.dataView_.getUint8(0) & 0xe0)) {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.JS_INTEGER_OVERFLOW);
}
let value = 0;
for (let i = 0; i < this.dataView_.byteLength; i++) {
let chunk = this.dataView_.getUint8(i);
value = (256 * value) + chunk;
}
return value;
};
/**
* Interpret the element's data as a floating point number (32 bits or 64 bits).
* 80-bit floating point numbers are not supported.
* @throws {shaka.util.Error}
* @return {number}
*/
shaka.util.EbmlElement.prototype.getFloat = function() {
if (this.dataView_.byteLength == 4) {
return this.dataView_.getFloat32(0);
} else if (this.dataView_.byteLength == 8) {
return this.dataView_.getFloat64(0);
} else {
throw new shaka.util.Error(
shaka.util.Error.Severity.CRITICAL,
shaka.util.Error.Category.MEDIA,
shaka.util.Error.Code.EBML_BAD_FLOATING_POINT_SIZE);
}
};