Source: lib/util/mp4_parser.js

  1. /*! @license
  2.  * Shaka Player
  3.  * Copyright 2016 Google LLC
  4.  * SPDX-License-Identifier: Apache-2.0
  5.  */
  7. goog.provide('shaka.util.Mp4Parser');
  9. goog.require('goog.asserts');
  10. goog.require('shaka.log');
  11. goog.require('shaka.util.DataViewReader');
  14. /**
  15.  * @export
  16.  */
  17. shaka.util.Mp4Parser = class {
  18.   /** */
  19.   constructor() {
  20.     /** @private {!Object.<number, shaka.util.Mp4Parser.BoxType_>} */
  21.     this.headers_ = [];
  23.     /** @private {!Object.<number, !shaka.util.Mp4Parser.CallbackType>} */
  24.     this.boxDefinitions_ = [];
  26.     /** @private {boolean} */
  27.     this.done_ = false;
  28.   }
  31.   /**
  32.    * Declare a box type as a Box.
  33.    *
  34.    * @param {string} type
  35.    * @param {!shaka.util.Mp4Parser.CallbackType} definition
  36.    * @return {!shaka.util.Mp4Parser}
  37.    * @export
  38.    */
  39.   box(type, definition) {
  40.     const typeCode = shaka.util.Mp4Parser.typeFromString_(type);
  41.     this.headers_[typeCode] = shaka.util.Mp4Parser.BoxType_.BASIC_BOX;
  42.     this.boxDefinitions_[typeCode] = definition;
  43.     return this;
  44.   }
  47.   /**
  48.    * Declare a box type as a Full Box.
  49.    *
  50.    * @param {string} type
  51.    * @param {!shaka.util.Mp4Parser.CallbackType} definition
  52.    * @return {!shaka.util.Mp4Parser}
  53.    * @export
  54.    */
  55.   fullBox(type, definition) {
  56.     const typeCode = shaka.util.Mp4Parser.typeFromString_(type);
  57.     this.headers_[typeCode] = shaka.util.Mp4Parser.BoxType_.FULL_BOX;
  58.     this.boxDefinitions_[typeCode] = definition;
  59.     return this;
  60.   }
  63.   /**
  64.    * Stop parsing.  Useful for extracting information from partial segments and
  65.    * avoiding an out-of-bounds error once you find what you are looking for.
  66.    *
  67.    * @export
  68.    */
  69.   stop() {
  70.     this.done_ = true;
  71.   }
  74.   /**
  75.    * Parse the given data using the added callbacks.
  76.    *
  77.    * @param {!BufferSource} data
  78.    * @param {boolean=} partialOkay If true, allow reading partial payloads
  79.    *   from some boxes. If the goal is a child box, we can sometimes find it
  80.    *   without enough data to find all child boxes.
  81.    * @param {boolean=} stopOnPartial If true, stop reading if an incomplete
  82.    *   box is detected.
  83.    * @export
  84.    */
  85.   parse(data, partialOkay, stopOnPartial) {
  86.     const reader = new shaka.util.DataViewReader(
  87.         data, shaka.util.DataViewReader.Endianness.BIG_ENDIAN);
  89.     this.done_ = false;
  90.     while (reader.hasMoreData() && !this.done_) {
  91.       this.parseNext(0, reader, partialOkay, stopOnPartial);
  92.     }
  93.   }
  96.   /**
  97.    * Parse the next box on the current level.
  98.    *
  99.    * @param {number} absStart The absolute start position in the original
  100.    *   byte array.
  101.    * @param {!shaka.util.DataViewReader} reader
  102.    * @param {boolean=} partialOkay If true, allow reading partial payloads
  103.    *   from some boxes. If the goal is a child box, we can sometimes find it
  104.    *   without enough data to find all child boxes.
  105.    * @param {boolean=} stopOnPartial If true, stop reading if an incomplete
  106.    *   box is detected.
  107.    * @export
  108.    */
  109.   parseNext(absStart, reader, partialOkay, stopOnPartial) {
  110.     const start = reader.getPosition();
  112.     // size(4 bytes) + type(4 bytes) = 8 bytes
  113.     if (stopOnPartial && start + 8 > reader.getLength()) {
  114.       this.done_ = true;
  115.       return;
  116.     }
  118.     let size = reader.readUint32();
  119.     const type = reader.readUint32();
  120.     const name = shaka.util.Mp4Parser.typeToString(type);
  121.     let has64BitSize = false;
  122.     shaka.log.v2('Parsing MP4 box', name);
  124.     switch (size) {
  125.       case 0:
  126.         size = reader.getLength() - start;
  127.         break;
  128.       case 1:
  129.         if (stopOnPartial && reader.getPosition() + 8 > reader.getLength()) {
  130.           this.done_ = true;
  131.           return;
  132.         }
  133.         size = reader.readUint64();
  134.         has64BitSize = true;
  135.         break;
  136.     }
  138.     const boxDefinition = this.boxDefinitions_[type];
  140.     if (boxDefinition) {
  141.       let version = null;
  142.       let flags = null;
  144.       if (this.headers_[type] == shaka.util.Mp4Parser.BoxType_.FULL_BOX) {
  145.         if (stopOnPartial && reader.getPosition() + 4 > reader.getLength()) {
  146.           this.done_ = true;
  147.           return;
  148.         }
  149.         const versionAndFlags = reader.readUint32();
  150.         version = versionAndFlags >>> 24;
  151.         flags = versionAndFlags & 0xFFFFFF;
  152.       }
  154.       // Read the whole payload so that the current level can be safely read
  155.       // regardless of how the payload is parsed.
  156.       let end = start + size;
  157.       if (partialOkay && end > reader.getLength()) {
  158.         // For partial reads, truncate the payload if we must.
  159.         end = reader.getLength();
  160.       }
  162.       if (stopOnPartial && end > reader.getLength()) {
  163.         this.done_ = true;
  164.         return;
  165.       }
  166.       const payloadSize = end - reader.getPosition();
  167.       const payload =
  168.       (payloadSize > 0) ? reader.readBytes(payloadSize) : new Uint8Array(0);
  170.       const payloadReader = new shaka.util.DataViewReader(
  171.           payload, shaka.util.DataViewReader.Endianness.BIG_ENDIAN);
  173.       /** @type {shaka.extern.ParsedBox} */
  174.       const box = {
  175.         parser: this,
  176.         partialOkay: partialOkay || false,
  177.         version,
  178.         flags,
  179.         reader: payloadReader,
  180.         size,
  181.         start: start + absStart,
  182.         has64BitSize,
  183.       };
  185.       boxDefinition(box);
  186.     } else {
  187.       // Move the read head to be at the end of the box.
  188.       // If the box is longer than the remaining parts of the file, e.g. the
  189.       // mp4 is improperly formatted, or this was a partial range request that
  190.       // ended in the middle of a box, just skip to the end.
  191.       const skipLength = Math.min(
  192.           start + size - reader.getPosition(),
  193.           reader.getLength() - reader.getPosition());
  194.       reader.skip(skipLength);
  195.     }
  196.   }
  199.   /**
  200.    * A callback that tells the Mp4 parser to treat the body of a box as a series
  201.    * of boxes. The number of boxes is limited by the size of the parent box.
  202.    *
  203.    * @param {!shaka.extern.ParsedBox} box
  204.    * @export
  205.    */
  206.   static children(box) {
  207.     // The "reader" starts at the payload, so we need to add the header to the
  208.     // start position.  The header size varies.
  209.     const headerSize = shaka.util.Mp4Parser.headerSize(box);
  210.     while (box.reader.hasMoreData() && !box.parser.done_) {
  211.       box.parser.parseNext(box.start + headerSize, box.reader, box.partialOkay);
  212.     }
  213.   }
  216.   /**
  217.    * A callback that tells the Mp4 parser to treat the body of a box as a sample
  218.    * description. A sample description box has a fixed number of children. The
  219.    * number of children is represented by a 4 byte unsigned integer. Each child
  220.    * is a box.
  221.    *
  222.    * @param {!shaka.extern.ParsedBox} box
  223.    * @export
  224.    */
  225.   static sampleDescription(box) {
  226.     // The "reader" starts at the payload, so we need to add the header to the
  227.     // start position.  The header size varies.
  228.     const headerSize = shaka.util.Mp4Parser.headerSize(box);
  229.     const count = box.reader.readUint32();
  230.     for (let i = 0; i < count; i++) {
  231.       box.parser.parseNext(box.start + headerSize, box.reader, box.partialOkay);
  232.       if (box.parser.done_) {
  233.         break;
  234.       }
  235.     }
  236.   }
  239.   /**
  240.    * Create a callback that tells the Mp4 parser to treat the body of a box as a
  241.    * binary blob and to parse the body's contents using the provided callback.
  242.    *
  243.    * @param {function(!Uint8Array)} callback
  244.    * @return {!shaka.util.Mp4Parser.CallbackType}
  245.    * @export
  246.    */
  247.   static allData(callback) {
  248.     return (box) => {
  249.       const all = box.reader.getLength() - box.reader.getPosition();
  250.       callback(box.reader.readBytes(all));
  251.     };
  252.   }
  255.   /**
  256.    * Convert an ascii string name to the integer type for a box.
  257.    *
  258.    * @param {string} name The name of the box. The name must be four
  259.    *                      characters long.
  260.    * @return {number}
  261.    * @private
  262.    */
  263.   static typeFromString_(name) {
  264.     goog.asserts.assert(
  265.         name.length == 4,
  266.         'Mp4 box names must be 4 characters long');
  268.     let code = 0;
  269.     for (const chr of name) {
  270.       code = (code << 8) | chr.charCodeAt(0);
  271.     }
  272.     return code;
  273.   }
  276.   /**
  277.    * Convert an integer type from a box into an ascii string name.
  278.    * Useful for debugging.
  279.    *
  280.    * @param {number} type The type of the box, a uint32.
  281.    * @return {string}
  282.    * @export
  283.    */
  284.   static typeToString(type) {
  285.     const name = String.fromCharCode(
  286.         (type >> 24) & 0xff,
  287.         (type >> 16) & 0xff,
  288.         (type >> 8) & 0xff,
  289.         type & 0xff);
  290.     return name;
  291.   }
  293.   /**
  294.    * Find the header size of the box.
  295.    * Useful for modifying boxes in place or finding the exact offset of a field.
  296.    *
  297.    * @param {shaka.extern.ParsedBox} box
  298.    * @return {number}
  299.    * @export
  300.    */
  301.   static headerSize(box) {
  302.     const basicHeaderSize = 8;
  303.     const _64BitFieldSize = box.has64BitSize ? 8 : 0;
  304.     const versionAndFlagsSize = box.flags != null ? 4 : 0;
  305.     return basicHeaderSize + _64BitFieldSize + versionAndFlagsSize;
  306.   }
  307. };
  310. /**
  311.  * @typedef {function(!shaka.extern.ParsedBox)}
  312.  * @exportInterface
  313.  */
  314. shaka.util.Mp4Parser.CallbackType;
  317. /**
  318.  * An enum used to track the type of box so that the correct values can be
  319.  * read from the header.
  320.  *
  321.  * @enum {number}
  322.  * @private
  323.  */
  324. shaka.util.Mp4Parser.BoxType_ = {
  325.   BASIC_BOX: 0,
  326.   FULL_BOX: 1,
  327. };