import FactoryMaker from '../../core/FactoryMaker';
/**
* Creates an instance of an EBMLParser class which implements a large subset
* of the functionality required to parse Matroska EBML
*
* @param {Object} config object with data member which is the buffer to parse
*/
function EBMLParser(config) {
let instance;
let data = new DataView(config.data);
let pos = 0;
function getPos() {
return pos;
}
function setPos(value) {
pos = value;
}
/**
* Consumes an EBML tag from the data stream.
*
* @param {Object} tag to parse, A tag is an object with at least a {number} tag and
* {boolean} required flag.
* @param {boolean} test whether or not the function should throw if a required
* tag is not found
* @return {boolean} whether or not the tag was found
* @throws will throw an exception if a required tag is not found and test
* param is false or undefined, or if the stream is malformed.
* @memberof EBMLParser
*/
function consumeTag(tag, test) {
let found = true;
let bytesConsumed = 0;
let p1,
p2;
if (test === undefined) {
test = false;
}
if (tag.tag > 0xFFFFFF) {
if (data.getUint32(pos) !== tag.tag) {
found = false;
}
bytesConsumed = 4;
} else if (tag.tag > 0xFFFF) {
// 3 bytes
p1 = data.getUint16(pos);
p2 = data.getUint8(pos + 2);
// shift p1 over a byte and add p2
if (p1 * 256 + p2 !== tag.tag) {
found = false;
}
bytesConsumed = 3;
} else if (tag.tag > 0xFF) {
if (data.getUint16(pos) !== tag.tag) {
found = false;
}
bytesConsumed = 2;
} else {
if (data.getUint8(pos) !== tag.tag) {
found = false;
}
bytesConsumed = 1;
}
if (!found && tag.required && !test) {
throw new Error('required tag not found');
}
if (found) {
pos += bytesConsumed;
}
return found;
}
/**
* Consumes an EBML tag from the data stream. If the tag is found then this
* function will also remove the size field which follows the tag from the
* data stream.
*
* @param {Object} tag to parse, A tag is an object with at least a {number} tag and
* {boolean} required flag.
* @param {boolean} test whether or not the function should throw if a required
* tag is not found
* @return {boolean} whether or not the tag was found
* @throws will throw an exception if a required tag is not found and test
* param is false or undefined, or if the stream is malformedata.
* @memberof EBMLParser
*/
function consumeTagAndSize(tag, test) {
let found = consumeTag(tag, test);
if (found) {
getMatroskaCodedNum();
}
return found;
}
/**
* Consumes an EBML tag from the data stream. If the tag is found then this
* function will also remove the size field which follows the tag from the
* data stream. It will use the value of the size field to parse a binary
* field, using a parser defined in the tag itself
*
* @param {Object} tag to parse, A tag is an object with at least a {number} tag,
* {boolean} required flag, and a parse function which takes a size parameter
* @return {boolean} whether or not the tag was found
* @throws will throw an exception if a required tag is not found,
* or if the stream is malformed
* @memberof EBMLParser
*/
function parseTag(tag) {
let size;
consumeTag(tag);
size = getMatroskaCodedNum();
return instance[tag.parse](size);
}
/**
* Consumes an EBML tag from the data stream. If the tag is found then this
* function will also remove the size field which follows the tag from the
* data stream. It will use the value of the size field to skip over the
* entire section of EBML encapsulated by the tag.
*
* @param {Object} tag to parse, A tag is an object with at least a {number} tag, and
* {boolean} required flag
* @param {boolean} test a flag to indicate if an exception should be thrown
* if a required tag is not found
* @return {boolean} whether or not the tag was found
* @throws will throw an exception if a required tag is not found and test is
* false or undefined or if the stream is malformed
* @memberof EBMLParser
*/
function skipOverElement(tag, test) {
let found = consumeTag(tag, test);
let headerSize;
if (found) {
headerSize = getMatroskaCodedNum();
pos += headerSize;
}
return found;
}
/**
* Returns and consumes a number encoded according to the Matroska EBML
* specification from the bitstream.
*
* @param {boolean} retainMSB whether or not to retain the Most Significant Bit (the
* first 1). this is usually true when reading Tag IDs.
* @return {number} the decoded number
* @throws will throw an exception if the bit stream is malformed or there is
* not enough data
* @memberof EBMLParser
*/
function getMatroskaCodedNum(retainMSB) {
let bytesUsed = 1;
let mask = 0x80;
let maxBytes = 8;
let extraBytes = -1;
let num = 0;
let ch = data.getUint8(pos);
let i = 0;
for (i = 0; i < maxBytes; i += 1) {
if ((ch & mask) === mask) {
num = (retainMSB === undefined) ? ch & ~mask : ch;
extraBytes = i;
break;
}
mask >>= 1;
}
for (i = 0; i < extraBytes; i += 1, bytesUsed += 1) {
num = (num << 8) | (0xff & data.getUint8(pos + bytesUsed));
}
pos += bytesUsed;
return num;
}
/**
* Returns and consumes a float from the bitstream.
*
* @param {number} size 4 or 8 byte floats are supported
* @return {number} the decoded number
* @throws will throw an exception if the bit stream is malformed or there is
* not enough data
* @memberof EBMLParser
*/
function getMatroskaFloat(size) {
let outFloat;
switch (size) {
case 4:
outFloat = data.getFloat32(pos);
pos += 4;
break;
case 8:
outFloat = data.getFloat64(pos);
pos += 8;
break;
}
return outFloat;
}
/**
* Consumes and returns an unsigned int from the bitstream.
*
* @param {number} size 1 to 8 bytes
* @return {number} the decoded number
* @throws will throw an exception if the bit stream is malformed or there is
* not enough data
* @memberof EBMLParser
*/
function getMatroskaUint(size) {
let val = 0;
for (let i = 0; i < size; i += 1) {
val <<= 8;
val |= data.getUint8(pos + i) & 0xff;
}
pos += size;
return val;
}
/**
* Tests whether there is more data in the bitstream for parsing
*
* @return {boolean} whether there is more data to parse
* @memberof EBMLParser
*/
function moreData() {
return pos < data.byteLength;
}
instance = {
getPos: getPos,
setPos: setPos,
consumeTag: consumeTag,
consumeTagAndSize: consumeTagAndSize,
parseTag: parseTag,
skipOverElement: skipOverElement,
getMatroskaCodedNum: getMatroskaCodedNum,
getMatroskaFloat: getMatroskaFloat,
getMatroskaUint: getMatroskaUint,
moreData: moreData
};
return instance;
}
EBMLParser.__dashjs_factory_name = 'EBMLParser';
export default FactoryMaker.getClassFactory(EBMLParser);