pdf.js/src/core/obj.js

/* Copyright 2012 Mozilla Foundation
 *
 * 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.
 */

import {
  assert, bytesToString, createPromiseCapability, createValidAbsoluteUrl, error,
  info, InvalidPDFException, isArray, isBool, isInt, isString,
  MissingDataException, shadow, stringToPDFString, stringToUTF8String, Util,
  warn, XRefParseException
} from '../shared/util';
import {
  Dict, isCmd, isDict, isName, isRef, isRefsEqual, isStream, Ref, RefSet,
  RefSetCache
} from './primitives';
import { Lexer, Parser } from './parser';
import { ChunkedStream } from './chunked_stream';
import { CipherTransformFactory } from './crypto';
import { ColorSpace } from './colorspace';

var Catalog = (function CatalogClosure() {
  function Catalog(pdfManager, xref, pageFactory) {
    this.pdfManager = pdfManager;
    this.xref = xref;
    this.catDict = xref.getCatalogObj();
    assert(isDict(this.catDict), 'catalog object is not a dictionary');

    this.fontCache = new RefSetCache();
    this.builtInCMapCache = Object.create(null);
    this.pageKidsCountCache = new RefSetCache();
    // TODO refactor to move getPage() to the PDFDocument.
    this.pageFactory = pageFactory;
    this.pagePromises = [];
  }

  Catalog.prototype = {
    get metadata() {
      var streamRef = this.catDict.getRaw('Metadata');
      if (!isRef(streamRef)) {
        return shadow(this, 'metadata', null);
      }

      var encryptMetadata = (!this.xref.encrypt ? false :
                             this.xref.encrypt.encryptMetadata);

      var stream = this.xref.fetch(streamRef, !encryptMetadata);
      var metadata;
      if (stream && isDict(stream.dict)) {
        var type = stream.dict.get('Type');
        var subtype = stream.dict.get('Subtype');

        if (isName(type, 'Metadata') && isName(subtype, 'XML')) {
          // XXX: This should examine the charset the XML document defines,
          // however since there are currently no real means to decode
          // arbitrary charsets, let's just hope that the author of the PDF
          // was reasonable enough to stick with the XML default charset,
          // which is UTF-8.
          try {
            metadata = stringToUTF8String(bytesToString(stream.getBytes()));
          } catch (e) {
            if (e instanceof MissingDataException) {
              throw e;
            }
            info('Skipping invalid metadata.');
          }
        }
      }

      return shadow(this, 'metadata', metadata);
    },
    get toplevelPagesDict() {
      var pagesObj = this.catDict.get('Pages');
      assert(isDict(pagesObj), 'invalid top-level pages dictionary');
      // shadow the prototype getter
      return shadow(this, 'toplevelPagesDict', pagesObj);
    },
    get documentOutline() {
      var obj = null;
      try {
        obj = this.readDocumentOutline();
      } catch (ex) {
        if (ex instanceof MissingDataException) {
          throw ex;
        }
        warn('Unable to read document outline');
      }
      return shadow(this, 'documentOutline', obj);
    },
    readDocumentOutline: function Catalog_readDocumentOutline() {
      var obj = this.catDict.get('Outlines');
      if (!isDict(obj)) {
        return null;
      }
      obj = obj.getRaw('First');
      if (!isRef(obj)) {
        return null;
      }
      var root = { items: [], };
      var queue = [{ obj, parent: root, }];
      // To avoid recursion, keep track of the already processed items.
      var processed = new RefSet();
      processed.put(obj);
      var xref = this.xref, blackColor = new Uint8Array(3);

      while (queue.length > 0) {
        var i = queue.shift();
        var outlineDict = xref.fetchIfRef(i.obj);
        if (outlineDict === null) {
          continue;
        }
        assert(outlineDict.has('Title'), 'Invalid outline item');

        var data = { url: null, dest: null, };
        Catalog.parseDestDictionary({
          destDict: outlineDict,
          resultObj: data,
          docBaseUrl: this.pdfManager.docBaseUrl,
        });
        var title = outlineDict.get('Title');
        var flags = outlineDict.get('F') || 0;

        var color = outlineDict.getArray('C'), rgbColor = blackColor;
        // We only need to parse the color when it's valid, and non-default.
        if (isArray(color) && color.length === 3 &&
            (color[0] !== 0 || color[1] !== 0 || color[2] !== 0)) {
          rgbColor = ColorSpace.singletons.rgb.getRgb(color, 0);
        }
        var outlineItem = {
          dest: data.dest,
          url: data.url,
          unsafeUrl: data.unsafeUrl,
          newWindow: data.newWindow,
          title: stringToPDFString(title),
          color: rgbColor,
          count: outlineDict.get('Count'),
          bold: !!(flags & 2),
          italic: !!(flags & 1),
          items: [],
        };
        i.parent.items.push(outlineItem);
        obj = outlineDict.getRaw('First');
        if (isRef(obj) && !processed.has(obj)) {
          queue.push({ obj, parent: outlineItem, });
          processed.put(obj);
        }
        obj = outlineDict.getRaw('Next');
        if (isRef(obj) && !processed.has(obj)) {
          queue.push({ obj, parent: i.parent, });
          processed.put(obj);
        }
      }
      return (root.items.length > 0 ? root.items : null);
    },
    get numPages() {
      var obj = this.toplevelPagesDict.get('Count');
      assert(
        isInt(obj),
        'page count in top level pages object is not an integer'
      );
      // shadow the prototype getter
      return shadow(this, 'num', obj);
    },
    get destinations() {
      function fetchDestination(dest) {
        return isDict(dest) ? dest.get('D') : dest;
      }

      var xref = this.xref;
      var dests = {}, nameTreeRef, nameDictionaryRef;
      var obj = this.catDict.get('Names');
      if (obj && obj.has('Dests')) {
        nameTreeRef = obj.getRaw('Dests');
      } else if (this.catDict.has('Dests')) {
        nameDictionaryRef = this.catDict.get('Dests');
      }

      if (nameDictionaryRef) {
        // reading simple destination dictionary
        obj = nameDictionaryRef;
        obj.forEach(function catalogForEach(key, value) {
          if (!value) {
            return;
          }
          dests[key] = fetchDestination(value);
        });
      }
      if (nameTreeRef) {
        var nameTree = new NameTree(nameTreeRef, xref);
        var names = nameTree.getAll();
        for (var name in names) {
          dests[name] = fetchDestination(names[name]);
        }
      }
      return shadow(this, 'destinations', dests);
    },
    getDestination: function Catalog_getDestination(destinationId) {
      function fetchDestination(dest) {
        return isDict(dest) ? dest.get('D') : dest;
      }

      var xref = this.xref;
      var dest = null, nameTreeRef, nameDictionaryRef;
      var obj = this.catDict.get('Names');
      if (obj && obj.has('Dests')) {
        nameTreeRef = obj.getRaw('Dests');
      } else if (this.catDict.has('Dests')) {
        nameDictionaryRef = this.catDict.get('Dests');
      }

      if (nameDictionaryRef) { // Simple destination dictionary.
        var value = nameDictionaryRef.get(destinationId);
        if (value) {
          dest = fetchDestination(value);
        }
      }
      if (nameTreeRef) {
        var nameTree = new NameTree(nameTreeRef, xref);
        dest = fetchDestination(nameTree.get(destinationId));
      }
      return dest;
    },

    get pageLabels() {
      var obj = null;
      try {
        obj = this.readPageLabels();
      } catch (ex) {
        if (ex instanceof MissingDataException) {
          throw ex;
        }
        warn('Unable to read page labels.');
      }
      return shadow(this, 'pageLabels', obj);
    },
    readPageLabels: function Catalog_readPageLabels() {
      var obj = this.catDict.getRaw('PageLabels');
      if (!obj) {
        return null;
      }
      var pageLabels = new Array(this.numPages);
      var style = null;
      var prefix = '';

      var numberTree = new NumberTree(obj, this.xref);
      var nums = numberTree.getAll();
      var currentLabel = '', currentIndex = 1;

      for (var i = 0, ii = this.numPages; i < ii; i++) {
        if (i in nums) {
          var labelDict = nums[i];
          assert(isDict(labelDict), 'The PageLabel is not a dictionary.');

          var type = labelDict.get('Type');
          assert(!type || isName(type, 'PageLabel'),
                 'Invalid type in PageLabel dictionary.');

          var s = labelDict.get('S');
          assert(!s || isName(s), 'Invalid style in PageLabel dictionary.');
          style = s ? s.name : null;

          var p = labelDict.get('P');
          assert(!p || isString(p), 'Invalid prefix in PageLabel dictionary.');
          prefix = p ? stringToPDFString(p) : '';

          var st = labelDict.get('St');
          assert(!st || (isInt(st) && st >= 1),
                 'Invalid start in PageLabel dictionary.');
          currentIndex = st || 1;
        }

        switch (style) {
          case 'D':
            currentLabel = currentIndex;
            break;
          case 'R':
          case 'r':
            currentLabel = Util.toRoman(currentIndex, style === 'r');
            break;
          case 'A':
          case 'a':
            var LIMIT = 26; // Use only the characters A--Z, or a--z.
            var A_UPPER_CASE = 0x41, A_LOWER_CASE = 0x61;

            var baseCharCode = (style === 'a' ? A_LOWER_CASE : A_UPPER_CASE);
            var letterIndex = currentIndex - 1;
            var character = String.fromCharCode(baseCharCode +
                                                (letterIndex % LIMIT));
            var charBuf = [];
            for (var j = 0, jj = (letterIndex / LIMIT) | 0; j <= jj; j++) {
              charBuf.push(character);
            }
            currentLabel = charBuf.join('');
            break;
          default:
            assert(!style,
                   'Invalid style "' + style + '" in PageLabel dictionary.');
        }
        pageLabels[i] = prefix + currentLabel;

        currentLabel = '';
        currentIndex++;
      }
      return pageLabels;
    },

    get attachments() {
      var xref = this.xref;
      var attachments = null, nameTreeRef;
      var obj = this.catDict.get('Names');
      if (obj) {
        nameTreeRef = obj.getRaw('EmbeddedFiles');
      }

      if (nameTreeRef) {
        var nameTree = new NameTree(nameTreeRef, xref);
        var names = nameTree.getAll();
        for (var name in names) {
          var fs = new FileSpec(names[name], xref);
          if (!attachments) {
            attachments = Object.create(null);
          }
          attachments[stringToPDFString(name)] = fs.serializable;
        }
      }
      return shadow(this, 'attachments', attachments);
    },
    get javaScript() {
      var xref = this.xref;
      var obj = this.catDict.get('Names');

      var javaScript = [];
      function appendIfJavaScriptDict(jsDict) {
        var type = jsDict.get('S');
        if (!isName(type, 'JavaScript')) {
          return;
        }
        var js = jsDict.get('JS');
        if (isStream(js)) {
          js = bytesToString(js.getBytes());
        } else if (!isString(js)) {
          return;
        }
        javaScript.push(stringToPDFString(js));
      }
      if (obj && obj.has('JavaScript')) {
        var nameTree = new NameTree(obj.getRaw('JavaScript'), xref);
        var names = nameTree.getAll();
        for (var name in names) {
          // We don't really use the JavaScript right now. This code is
          // defensive so we don't cause errors on document load.
          var jsDict = names[name];
          if (isDict(jsDict)) {
            appendIfJavaScriptDict(jsDict);
          }
        }
      }

      // Append OpenAction actions to javaScript array
      var openactionDict = this.catDict.get('OpenAction');
      if (isDict(openactionDict, 'Action')) {
        var actionType = openactionDict.get('S');
        if (isName(actionType, 'Named')) {
          // The named Print action is not a part of the PDF 1.7 specification,
          // but is supported by many PDF readers/writers (including Adobe's).
          var action = openactionDict.get('N');
          if (isName(action, 'Print')) {
            javaScript.push('print({});');
          }
        } else {
          appendIfJavaScriptDict(openactionDict);
        }
      }

      return shadow(this, 'javaScript', javaScript);
    },

    cleanup: function Catalog_cleanup() {
      this.pageKidsCountCache.clear();

      var promises = [];
      this.fontCache.forEach(function (promise) {
        promises.push(promise);
      });
      return Promise.all(promises).then((translatedFonts) => {
        for (var i = 0, ii = translatedFonts.length; i < ii; i++) {
          var font = translatedFonts[i].dict;
          delete font.translated;
        }
        this.fontCache.clear();
        this.builtInCMapCache = Object.create(null);
      });
    },

    getPage: function Catalog_getPage(pageIndex) {
      if (!(pageIndex in this.pagePromises)) {
        this.pagePromises[pageIndex] = this.getPageDict(pageIndex).then(
            ([dict, ref]) => {
          return this.pageFactory.createPage(pageIndex, dict, ref,
                                             this.fontCache,
                                             this.builtInCMapCache);
        });
      }
      return this.pagePromises[pageIndex];
    },

    getPageDict: function Catalog_getPageDict(pageIndex) {
      var capability = createPromiseCapability();
      var nodesToVisit = [this.catDict.getRaw('Pages')];
      var count, currentPageIndex = 0;
      var xref = this.xref, pageKidsCountCache = this.pageKidsCountCache;

      function next() {
        while (nodesToVisit.length) {
          var currentNode = nodesToVisit.pop();

          if (isRef(currentNode)) {
            count = pageKidsCountCache.get(currentNode);
            // Skip nodes where the page can't be.
            if (count > 0 && currentPageIndex + count < pageIndex) {
              currentPageIndex += count;
              continue;
            }

            xref.fetchAsync(currentNode).then(function (obj) {
              if (isDict(obj, 'Page') || (isDict(obj) && !obj.has('Kids'))) {
                if (pageIndex === currentPageIndex) {
                  // Cache the Page reference, since it can *greatly* improve
                  // performance by reducing redundant lookups in long documents
                  // where all nodes are found at *one* level of the tree.
                  if (currentNode && !pageKidsCountCache.has(currentNode)) {
                    pageKidsCountCache.put(currentNode, 1);
                  }
                  capability.resolve([obj, currentNode]);
                } else {
                  currentPageIndex++;
                  next();
                }
                return;
              }
              nodesToVisit.push(obj);
              next();
            }, capability.reject);
            return;
          }

          // Must be a child page dictionary.
          assert(isDict(currentNode),
            'page dictionary kid reference points to wrong type of object');

          count = currentNode.get('Count');
          // Cache the Kids count, since it can reduce redundant lookups in long
          // documents where all nodes are found at *one* level of the tree.
          var objId = currentNode.objId;
          if (objId && !pageKidsCountCache.has(objId)) {
            pageKidsCountCache.put(objId, count);
          }
          // Skip nodes where the page can't be.
          if (currentPageIndex + count <= pageIndex) {
            currentPageIndex += count;
            continue;
          }

          var kids = currentNode.get('Kids');
          assert(isArray(kids), 'page dictionary kids object is not an array');

          // Always check all `Kids` nodes, to avoid getting stuck in an empty
          // node further down in the tree (see issue5644.pdf, issue8088.pdf),
          // and to ensure that we actually find the correct `Page` dict.
          for (var last = kids.length - 1; last >= 0; last--) {
            nodesToVisit.push(kids[last]);
          }
        }
        capability.reject('Page index ' + pageIndex + ' not found.');
      }
      next();
      return capability.promise;
    },

    getPageIndex: function Catalog_getPageIndex(pageRef) {
      // The page tree nodes have the count of all the leaves below them. To get
      // how many pages are before we just have to walk up the tree and keep
      // adding the count of siblings to the left of the node.
      var xref = this.xref;
      function pagesBeforeRef(kidRef) {
        var total = 0;
        var parentRef;
        return xref.fetchAsync(kidRef).then(function (node) {
          if (isRefsEqual(kidRef, pageRef) && !isDict(node, 'Page') &&
              !(isDict(node) && !node.has('Type') && node.has('Contents'))) {
            throw new Error('The reference does not point to a /Page Dict.');
          }
          if (!node) {
            return null;
          }
          assert(isDict(node), 'node must be a Dict.');
          parentRef = node.getRaw('Parent');
          return node.getAsync('Parent');
        }).then(function (parent) {
          if (!parent) {
            return null;
          }
          assert(isDict(parent), 'parent must be a Dict.');
          return parent.getAsync('Kids');
        }).then(function (kids) {
          if (!kids) {
            return null;
          }
          var kidPromises = [];
          var found = false;
          for (var i = 0; i < kids.length; i++) {
            var kid = kids[i];
            assert(isRef(kid), 'kid must be a Ref.');
            if (kid.num === kidRef.num) {
              found = true;
              break;
            }
            kidPromises.push(xref.fetchAsync(kid).then(function (kid) {
              if (kid.has('Count')) {
                var count = kid.get('Count');
                total += count;
              } else { // page leaf node
                total++;
              }
            }));
          }
          if (!found) {
            error('kid ref not found in parents kids');
          }
          return Promise.all(kidPromises).then(function () {
            return [total, parentRef];
          });
        });
      }

      var total = 0;
      function next(ref) {
        return pagesBeforeRef(ref).then(function (args) {
          if (!args) {
            return total;
          }
          var count = args[0];
          var parentRef = args[1];
          total += count;
          return next(parentRef);
        });
      }

      return next(pageRef);
    },
  };

  /**
   * @typedef ParseDestDictionaryParameters
   * @property {Dict} destDict - The dictionary containing the destination.
   * @property {Object} resultObj - The object where the parsed destination
   *   properties will be placed.
   * @property {string} docBaseUrl - (optional) The document base URL that is
   *   used when attempting to recover valid absolute URLs from relative ones.
   */

  /**
   * Helper function used to parse the contents of destination dictionaries.
   * @param {ParseDestDictionaryParameters} params
   */
  Catalog.parseDestDictionary = function Catalog_parseDestDictionary(params) {
    // Lets URLs beginning with 'www.' default to using the 'http://' protocol.
    function addDefaultProtocolToUrl(url) {
      if (url.indexOf('www.') === 0) {
        return ('http://' + url);
      }
      return url;
    }
    // According to ISO 32000-1:2008, section 12.6.4.7, URIs should be encoded
    // in 7-bit ASCII. Some bad PDFs use UTF-8 encoding, see Bugzilla 1122280.
    function tryConvertUrlEncoding(url) {
      try {
        return stringToUTF8String(url);
      } catch (e) {
        return url;
      }
    }

    var destDict = params.destDict;
    if (!isDict(destDict)) {
      warn('Catalog_parseDestDictionary: "destDict" must be a dictionary.');
      return;
    }
    var resultObj = params.resultObj;
    if (typeof resultObj !== 'object') {
      warn('Catalog_parseDestDictionary: "resultObj" must be an object.');
      return;
    }
    var docBaseUrl = params.docBaseUrl || null;

    var action = destDict.get('A'), url, dest;
    if (isDict(action)) {
      var linkType = action.get('S').name;
      switch (linkType) {
        case 'URI':
          url = action.get('URI');
          if (isName(url)) {
            // Some bad PDFs do not put parentheses around relative URLs.
            url = '/' + url.name;
          } else if (isString(url)) {
            url = addDefaultProtocolToUrl(url);
          }
          // TODO: pdf spec mentions urls can be relative to a Base
          // entry in the dictionary.
          break;

        case 'GoTo':
          dest = action.get('D');
          break;

        case 'Launch':
          // We neither want, nor can, support arbitrary 'Launch' actions.
          // However, in practice they are mostly used for linking to other PDF
          // files, which we thus attempt to support (utilizing `docBaseUrl`).
          /* falls through */

        case 'GoToR':
          var urlDict = action.get('F');
          if (isDict(urlDict)) {
            // We assume that we found a FileSpec dictionary
            // and fetch the URL without checking any further.
            url = urlDict.get('F') || null;
          } else if (isString(urlDict)) {
            url = urlDict;
          }

          // NOTE: the destination is relative to the *remote* document.
          var remoteDest = action.get('D');
          if (remoteDest) {
            if (isName(remoteDest)) {
              remoteDest = remoteDest.name;
            }
            if (isString(url)) {
              let baseUrl = url.split('#')[0];
              if (isString(remoteDest)) {
                url = baseUrl + '#' + remoteDest;
              } else if (isArray(remoteDest)) {
                url = baseUrl + '#' + JSON.stringify(remoteDest);
              }
            }
          }
          // The 'NewWindow' property, equal to `LinkTarget.BLANK`.
          var newWindow = action.get('NewWindow');
          if (isBool(newWindow)) {
            resultObj.newWindow = newWindow;
          }
          break;

        case 'Named':
          var namedAction = action.get('N');
          if (isName(namedAction)) {
            resultObj.action = namedAction.name;
          }
          break;

        case 'JavaScript':
          var jsAction = action.get('JS'), js;
          if (isStream(jsAction)) {
            js = bytesToString(jsAction.getBytes());
          } else if (isString(jsAction)) {
            js = jsAction;
          }

          if (js) {
            // Attempt to recover valid URLs from 'JS' entries with certain
            // white-listed formats, e.g.
            //  - window.open('http://example.com')
            //  - app.launchURL('http://example.com', true)
            var URL_OPEN_METHODS = [
              'app.launchURL',
              'window.open'
            ];
            var regex = new RegExp(
              '^\\s*(' + URL_OPEN_METHODS.join('|').split('.').join('\\.') +
              ')\\((?:\'|\")([^\'\"]*)(?:\'|\")(?:,\\s*(\\w+)\\)|\\))', 'i');

            var jsUrl = regex.exec(stringToPDFString(js));
            if (jsUrl && jsUrl[2]) {
              url = jsUrl[2];

              if (jsUrl[3] === 'true' && jsUrl[1] === 'app.launchURL') {
                resultObj.newWindow = true;
              }
              break;
            }
          }
          /* falls through */
        default:
          warn('Catalog_parseDestDictionary: Unrecognized link type "' +
               linkType + '".');
          break;
      }
    } else if (destDict.has('Dest')) { // Simple destination link.
      dest = destDict.get('Dest');
    }

    if (isString(url)) {
      url = tryConvertUrlEncoding(url);
      var absoluteUrl = createValidAbsoluteUrl(url, docBaseUrl);
      if (absoluteUrl) {
        resultObj.url = absoluteUrl.href;
      }
      resultObj.unsafeUrl = url;
    }
    if (dest) {
      if (isName(dest)) {
        dest = dest.name;
      }
      if (isString(dest) || isArray(dest)) {
        resultObj.dest = dest;
      }
    }
  };

  return Catalog;
})();

var XRef = (function XRefClosure() {
  function XRef(stream, pdfManager) {
    this.stream = stream;
    this.pdfManager = pdfManager;
    this.entries = [];
    this.xrefstms = Object.create(null);
    // prepare the XRef cache
    this.cache = [];
    this.stats = {
      streamTypes: [],
      fontTypes: [],
    };
  }

  XRef.prototype = {
    setStartXRef: function XRef_setStartXRef(startXRef) {
      // Store the starting positions of xref tables as we process them
      // so we can recover from missing data errors
      this.startXRefQueue = [startXRef];
    },

    parse: function XRef_parse(recoveryMode) {
      var trailerDict;
      if (!recoveryMode) {
        trailerDict = this.readXRef();
      } else {
        warn('Indexing all PDF objects');
        trailerDict = this.indexObjects();
      }
      trailerDict.assignXref(this);
      this.trailer = trailerDict;
      var encrypt = trailerDict.get('Encrypt');
      if (isDict(encrypt)) {
        var ids = trailerDict.get('ID');
        var fileId = (ids && ids.length) ? ids[0] : '';
        // The 'Encrypt' dictionary itself should not be encrypted, and by
        // setting `suppressEncryption` we can prevent an infinite loop inside
        // of `XRef_fetchUncompressed` if the dictionary contains indirect
        // objects (fixes issue7665.pdf).
        encrypt.suppressEncryption = true;
        this.encrypt = new CipherTransformFactory(encrypt, fileId,
                                                  this.pdfManager.password);
      }

      // get the root dictionary (catalog) object
      if (!(this.root = trailerDict.get('Root'))) {
        error('Invalid root reference');
      }
    },

    processXRefTable: function XRef_processXRefTable(parser) {
      if (!('tableState' in this)) {
        // Stores state of the table as we process it so we can resume
        // from middle of table in case of missing data error
        this.tableState = {
          entryNum: 0,
          streamPos: parser.lexer.stream.pos,
          parserBuf1: parser.buf1,
          parserBuf2: parser.buf2,
        };
      }

      var obj = this.readXRefTable(parser);

      // Sanity check
      if (!isCmd(obj, 'trailer')) {
        error('Invalid XRef table: could not find trailer dictionary');
      }
      // Read trailer dictionary, e.g.
      // trailer
      //    << /Size 22
      //      /Root 20R
      //      /Info 10R
      //      /ID [ <81b14aafa313db63dbd6f981e49f94f4> ]
      //    >>
      // The parser goes through the entire stream << ... >> and provides
      // a getter interface for the key-value table
      var dict = parser.getObj();

      // The pdflib PDF generator can generate a nested trailer dictionary
      if (!isDict(dict) && dict.dict) {
        dict = dict.dict;
      }
      if (!isDict(dict)) {
        error('Invalid XRef table: could not parse trailer dictionary');
      }
      delete this.tableState;

      return dict;
    },

    readXRefTable: function XRef_readXRefTable(parser) {
      // Example of cross-reference table:
      // xref
      // 0 1                    <-- subsection header (first obj #, obj count)
      // 0000000000 65535 f     <-- actual object (offset, generation #, f/n)
      // 23 2                   <-- subsection header ... and so on ...
      // 0000025518 00002 n
      // 0000025635 00000 n
      // trailer
      // ...

      var stream = parser.lexer.stream;
      var tableState = this.tableState;
      stream.pos = tableState.streamPos;
      parser.buf1 = tableState.parserBuf1;
      parser.buf2 = tableState.parserBuf2;

      // Outer loop is over subsection headers
      var obj;

      while (true) {
        if (!('firstEntryNum' in tableState) || !('entryCount' in tableState)) {
          if (isCmd(obj = parser.getObj(), 'trailer')) {
            break;
          }
          tableState.firstEntryNum = obj;
          tableState.entryCount = parser.getObj();
        }

        var first = tableState.firstEntryNum;
        var count = tableState.entryCount;
        if (!isInt(first) || !isInt(count)) {
          error('Invalid XRef table: wrong types in subsection header');
        }
        // Inner loop is over objects themselves
        for (var i = tableState.entryNum; i < count; i++) {
          tableState.streamPos = stream.pos;
          tableState.entryNum = i;
          tableState.parserBuf1 = parser.buf1;
          tableState.parserBuf2 = parser.buf2;

          var entry = {};
          entry.offset = parser.getObj();
          entry.gen = parser.getObj();
          var type = parser.getObj();

          if (isCmd(type, 'f')) {
            entry.free = true;
          } else if (isCmd(type, 'n')) {
            entry.uncompressed = true;
          }

          // Validate entry obj
          if (!isInt(entry.offset) || !isInt(entry.gen) ||
              !(entry.free || entry.uncompressed)) {
            error('Invalid entry in XRef subsection: ' + first + ', ' + count);
          }

          // The first xref table entry, i.e. obj 0, should be free. Attempting
          // to adjust an incorrect first obj # (fixes issue 3248 and 7229).
          if (i === 0 && entry.free && first === 1) {
            first = 0;
          }

          if (!this.entries[i + first]) {
            this.entries[i + first] = entry;
          }
        }

        tableState.entryNum = 0;
        tableState.streamPos = stream.pos;
        tableState.parserBuf1 = parser.buf1;
        tableState.parserBuf2 = parser.buf2;
        delete tableState.firstEntryNum;
        delete tableState.entryCount;
      }

      // Sanity check: as per spec, first object must be free
      if (this.entries[0] && !this.entries[0].free) {
        error('Invalid XRef table: unexpected first object');
      }
      return obj;
    },

    processXRefStream: function XRef_processXRefStream(stream) {
      if (!('streamState' in this)) {
        // Stores state of the stream as we process it so we can resume
        // from middle of stream in case of missing data error
        var streamParameters = stream.dict;
        var byteWidths = streamParameters.get('W');
        var range = streamParameters.get('Index');
        if (!range) {
          range = [0, streamParameters.get('Size')];
        }

        this.streamState = {
          entryRanges: range,
          byteWidths,
          entryNum: 0,
          streamPos: stream.pos,
        };
      }
      this.readXRefStream(stream);
      delete this.streamState;

      return stream.dict;
    },

    readXRefStream: function XRef_readXRefStream(stream) {
      var i, j;
      var streamState = this.streamState;
      stream.pos = streamState.streamPos;

      var byteWidths = streamState.byteWidths;
      var typeFieldWidth = byteWidths[0];
      var offsetFieldWidth = byteWidths[1];
      var generationFieldWidth = byteWidths[2];

      var entryRanges = streamState.entryRanges;
      while (entryRanges.length > 0) {
        var first = entryRanges[0];
        var n = entryRanges[1];

        if (!isInt(first) || !isInt(n)) {
          error('Invalid XRef range fields: ' + first + ', ' + n);
        }
        if (!isInt(typeFieldWidth) || !isInt(offsetFieldWidth) ||
            !isInt(generationFieldWidth)) {
          error('Invalid XRef entry fields length: ' + first + ', ' + n);
        }
        for (i = streamState.entryNum; i < n; ++i) {
          streamState.entryNum = i;
          streamState.streamPos = stream.pos;

          var type = 0, offset = 0, generation = 0;
          for (j = 0; j < typeFieldWidth; ++j) {
            type = (type << 8) | stream.getByte();
          }
          // if type field is absent, its default value is 1
          if (typeFieldWidth === 0) {
            type = 1;
          }
          for (j = 0; j < offsetFieldWidth; ++j) {
            offset = (offset << 8) | stream.getByte();
          }
          for (j = 0; j < generationFieldWidth; ++j) {
            generation = (generation << 8) | stream.getByte();
          }
          var entry = {};
          entry.offset = offset;
          entry.gen = generation;
          switch (type) {
            case 0:
              entry.free = true;
              break;
            case 1:
              entry.uncompressed = true;
              break;
            case 2:
              break;
            default:
              error('Invalid XRef entry type: ' + type);
          }
          if (!this.entries[first + i]) {
            this.entries[first + i] = entry;
          }
        }

        streamState.entryNum = 0;
        streamState.streamPos = stream.pos;
        entryRanges.splice(0, 2);
      }
    },

    indexObjects: function XRef_indexObjects() {
      // Simple scan through the PDF content to find objects,
      // trailers and XRef streams.
      var TAB = 0x9, LF = 0xA, CR = 0xD, SPACE = 0x20;
      var PERCENT = 0x25, LT = 0x3C;

      function readToken(data, offset) {
        var token = '', ch = data[offset];
        while (ch !== LF && ch !== CR && ch !== LT) {
          if (++offset >= data.length) {
            break;
          }
          token += String.fromCharCode(ch);
          ch = data[offset];
        }
        return token;
      }
      function skipUntil(data, offset, what) {
        var length = what.length, dataLength = data.length;
        var skipped = 0;
        // finding byte sequence
        while (offset < dataLength) {
          var i = 0;
          while (i < length && data[offset + i] === what[i]) {
            ++i;
          }
          if (i >= length) {
            break; // sequence found
          }
          offset++;
          skipped++;
        }
        return skipped;
      }
      var objRegExp = /^(\d+)\s+(\d+)\s+obj\b/;
      var trailerBytes = new Uint8Array([116, 114, 97, 105, 108, 101, 114]);
      var startxrefBytes = new Uint8Array([115, 116, 97, 114, 116, 120, 114,
                                          101, 102]);
      var endobjBytes = new Uint8Array([101, 110, 100, 111, 98, 106]);
      var xrefBytes = new Uint8Array([47, 88, 82, 101, 102]);

      // Clear out any existing entries, since they may be bogus.
      this.entries.length = 0;

      var stream = this.stream;
      stream.pos = 0;
      var buffer = stream.getBytes();
      var position = stream.start, length = buffer.length;
      var trailers = [], xrefStms = [];
      while (position < length) {
        var ch = buffer[position];
        if (ch === TAB || ch === LF || ch === CR || ch === SPACE) {
          ++position;
          continue;
        }
        if (ch === PERCENT) { // %-comment
          do {
            ++position;
            if (position >= length) {
              break;
            }
            ch = buffer[position];
          } while (ch !== LF && ch !== CR);
          continue;
        }
        var token = readToken(buffer, position);
        var m;
        if (token.indexOf('xref') === 0 &&
            (token.length === 4 || /\s/.test(token[4]))) {
          position += skipUntil(buffer, position, trailerBytes);
          trailers.push(position);
          position += skipUntil(buffer, position, startxrefBytes);
        } else if ((m = objRegExp.exec(token))) {
          if (typeof this.entries[m[1]] === 'undefined') {
            this.entries[m[1]] = {
              offset: position - stream.start,
              gen: m[2] | 0,
              uncompressed: true,
            };
          }
          var contentLength = skipUntil(buffer, position, endobjBytes) + 7;
          var content = buffer.subarray(position, position + contentLength);

          // checking XRef stream suspect
          // (it shall have '/XRef' and next char is not a letter)
          var xrefTagOffset = skipUntil(content, 0, xrefBytes);
          if (xrefTagOffset < contentLength &&
              content[xrefTagOffset + 5] < 64) {
            xrefStms.push(position - stream.start);
            this.xrefstms[position - stream.start] = 1; // Avoid recursion
          }

          position += contentLength;
        } else if (token.indexOf('trailer') === 0 &&
                   (token.length === 7 || /\s/.test(token[7]))) {
          trailers.push(position);
          position += skipUntil(buffer, position, startxrefBytes);
        } else {
          position += token.length + 1;
        }
      }
      // reading XRef streams
      var i, ii;
      for (i = 0, ii = xrefStms.length; i < ii; ++i) {
        this.startXRefQueue.push(xrefStms[i]);
        this.readXRef(/* recoveryMode */ true);
      }
      // finding main trailer
      var dict;
      for (i = 0, ii = trailers.length; i < ii; ++i) {
        stream.pos = trailers[i];
        var parser = new Parser(new Lexer(stream), /* allowStreams = */ true,
                                /* xref = */ this, /* recoveryMode = */ true);
        var obj = parser.getObj();
        if (!isCmd(obj, 'trailer')) {
          continue;
        }
        // read the trailer dictionary
        dict = parser.getObj();
        if (!isDict(dict)) {
          continue;
        }
        // taking the first one with 'ID'
        if (dict.has('ID')) {
          return dict;
        }
      }
      // no tailer with 'ID', taking last one (if exists)
      if (dict) {
        return dict;
      }
      // nothing helps
      // calling error() would reject worker with an UnknownErrorException.
      throw new InvalidPDFException('Invalid PDF structure');
    },

    readXRef: function XRef_readXRef(recoveryMode) {
      var stream = this.stream;

      try {
        while (this.startXRefQueue.length) {
          var startXRef = this.startXRefQueue[0];

          stream.pos = startXRef + stream.start;

          var parser = new Parser(new Lexer(stream), true, this);
          var obj = parser.getObj();
          var dict;

          // Get dictionary
          if (isCmd(obj, 'xref')) {
            // Parse end-of-file XRef
            dict = this.processXRefTable(parser);
            if (!this.topDict) {
              this.topDict = dict;
            }

            // Recursively get other XRefs 'XRefStm', if any
            obj = dict.get('XRefStm');
            if (isInt(obj)) {
              var pos = obj;
              // ignore previously loaded xref streams
              // (possible infinite recursion)
              if (!(pos in this.xrefstms)) {
                this.xrefstms[pos] = 1;
                this.startXRefQueue.push(pos);
              }
            }
          } else if (isInt(obj)) {
            // Parse in-stream XRef
            if (!isInt(parser.getObj()) ||
                !isCmd(parser.getObj(), 'obj') ||
                !isStream(obj = parser.getObj())) {
              error('Invalid XRef stream');
            }
            dict = this.processXRefStream(obj);
            if (!this.topDict) {
              this.topDict = dict;
            }
            if (!dict) {
              error('Failed to read XRef stream');
            }
          } else {
            error('Invalid XRef stream header');
          }

          // Recursively get previous dictionary, if any
          obj = dict.get('Prev');
          if (isInt(obj)) {
            this.startXRefQueue.push(obj);
          } else if (isRef(obj)) {
            // The spec says Prev must not be a reference, i.e. "/Prev NNN"
            // This is a fallback for non-compliant PDFs, i.e. "/Prev NNN 0 R"
            this.startXRefQueue.push(obj.num);
          }

          this.startXRefQueue.shift();
        }

        return this.topDict;
      } catch (e) {
        if (e instanceof MissingDataException) {
          throw e;
        }
        info('(while reading XRef): ' + e);
      }

      if (recoveryMode) {
        return;
      }
      throw new XRefParseException();
    },

    getEntry: function XRef_getEntry(i) {
      var xrefEntry = this.entries[i];
      if (xrefEntry && !xrefEntry.free && xrefEntry.offset) {
        return xrefEntry;
      }
      return null;
    },

    fetchIfRef: function XRef_fetchIfRef(obj, suppressEncryption) {
      if (!isRef(obj)) {
        return obj;
      }
      return this.fetch(obj, suppressEncryption);
    },

    fetch: function XRef_fetch(ref, suppressEncryption) {
      assert(isRef(ref), 'ref object is not a reference');
      var num = ref.num;
      if (num in this.cache) {
        var cacheEntry = this.cache[num];
        // In documents with Object Streams, it's possible that cached `Dict`s
        // have not been assigned an `objId` yet (see e.g. issue3115r.pdf).
        if (cacheEntry instanceof Dict && !cacheEntry.objId) {
          cacheEntry.objId = ref.toString();
        }
        return cacheEntry;
      }

      var xrefEntry = this.getEntry(num);

      // the referenced entry can be free
      if (xrefEntry === null) {
        return (this.cache[num] = null);
      }

      if (xrefEntry.uncompressed) {
        xrefEntry = this.fetchUncompressed(ref, xrefEntry, suppressEncryption);
      } else {
        xrefEntry = this.fetchCompressed(xrefEntry, suppressEncryption);
      }
      if (isDict(xrefEntry)) {
        xrefEntry.objId = ref.toString();
      } else if (isStream(xrefEntry)) {
        xrefEntry.dict.objId = ref.toString();
      }
      return xrefEntry;
    },

    fetchUncompressed: function XRef_fetchUncompressed(ref, xrefEntry,
                                                       suppressEncryption) {
      var gen = ref.gen;
      var num = ref.num;
      if (xrefEntry.gen !== gen) {
        error('inconsistent generation in XRef');
      }
      var stream = this.stream.makeSubStream(xrefEntry.offset +
                                             this.stream.start);
      var parser = new Parser(new Lexer(stream), true, this);
      var obj1 = parser.getObj();
      var obj2 = parser.getObj();
      var obj3 = parser.getObj();
      if (!isInt(obj1) || parseInt(obj1, 10) !== num ||
          !isInt(obj2) || parseInt(obj2, 10) !== gen ||
          !isCmd(obj3)) {
        error('bad XRef entry');
      }
      if (!isCmd(obj3, 'obj')) {
        // some bad PDFs use "obj1234" and really mean 1234
        if (obj3.cmd.indexOf('obj') === 0) {
          num = parseInt(obj3.cmd.substring(3), 10);
          if (!isNaN(num)) {
            return num;
          }
        }
        error('bad XRef entry');
      }
      if (this.encrypt && !suppressEncryption) {
        xrefEntry = parser.getObj(this.encrypt.createCipherTransform(num, gen));
      } else {
        xrefEntry = parser.getObj();
      }
      if (!isStream(xrefEntry)) {
        this.cache[num] = xrefEntry;
      }
      return xrefEntry;
    },

    fetchCompressed: function XRef_fetchCompressed(xrefEntry,
                                                   suppressEncryption) {
      var tableOffset = xrefEntry.offset;
      var stream = this.fetch(new Ref(tableOffset, 0));
      if (!isStream(stream)) {
        error('bad ObjStm stream');
      }
      var first = stream.dict.get('First');
      var n = stream.dict.get('N');
      if (!isInt(first) || !isInt(n)) {
        error('invalid first and n parameters for ObjStm stream');
      }
      var parser = new Parser(new Lexer(stream), false, this);
      parser.allowStreams = true;
      var i, entries = [], num, nums = [];
      // read the object numbers to populate cache
      for (i = 0; i < n; ++i) {
        num = parser.getObj();
        if (!isInt(num)) {
          error('invalid object number in the ObjStm stream: ' + num);
        }
        nums.push(num);
        var offset = parser.getObj();
        if (!isInt(offset)) {
          error('invalid object offset in the ObjStm stream: ' + offset);
        }
      }
      // read stream objects for cache
      for (i = 0; i < n; ++i) {
        entries.push(parser.getObj());
        // The ObjStm should not contain 'endobj'. If it's present, skip over it
        // to support corrupt PDFs (fixes issue 5241, bug 898610, bug 1037816).
        if (isCmd(parser.buf1, 'endobj')) {
          parser.shift();
        }
        num = nums[i];
        var entry = this.entries[num];
        if (entry && entry.offset === tableOffset && entry.gen === i) {
          this.cache[num] = entries[i];
        }
      }
      xrefEntry = entries[xrefEntry.gen];
      if (xrefEntry === undefined) {
        error('bad XRef entry for compressed object');
      }
      return xrefEntry;
    },

    fetchIfRefAsync: function XRef_fetchIfRefAsync(obj, suppressEncryption) {
      if (!isRef(obj)) {
        return Promise.resolve(obj);
      }
      return this.fetchAsync(obj, suppressEncryption);
    },

    fetchAsync: function XRef_fetchAsync(ref, suppressEncryption) {
      var streamManager = this.stream.manager;
      var xref = this;
      return new Promise(function tryFetch(resolve, reject) {
        try {
          resolve(xref.fetch(ref, suppressEncryption));
        } catch (e) {
          if (e instanceof MissingDataException) {
            streamManager.requestRange(e.begin, e.end).then(function () {
              tryFetch(resolve, reject);
            }, reject);
            return;
          }
          reject(e);
        }
      });
    },

    getCatalogObj: function XRef_getCatalogObj() {
      return this.root;
    },
  };

  return XRef;
})();

/**
 * A NameTree/NumberTree is like a Dict but has some advantageous properties,
 * see the specification (7.9.6 and 7.9.7) for additional details.
 * TODO: implement all the Dict functions and make this more efficient.
 */
var NameOrNumberTree = (function NameOrNumberTreeClosure() {
  function NameOrNumberTree(root, xref) {
    throw new Error('Cannot initialize NameOrNumberTree.');
  }

  NameOrNumberTree.prototype = {
    getAll: function NameOrNumberTree_getAll() {
      var dict = Object.create(null);
      if (!this.root) {
        return dict;
      }
      var xref = this.xref;
      // Reading Name/Number tree.
      var processed = new RefSet();
      processed.put(this.root);
      var queue = [this.root];
      while (queue.length > 0) {
        var i, n;
        var obj = xref.fetchIfRef(queue.shift());
        if (!isDict(obj)) {
          continue;
        }
        if (obj.has('Kids')) {
          var kids = obj.get('Kids');
          for (i = 0, n = kids.length; i < n; i++) {
            var kid = kids[i];
            assert(!processed.has(kid),
                   'Duplicate entry in "' + this._type + '" tree.');
            queue.push(kid);
            processed.put(kid);
          }
          continue;
        }
        var entries = obj.get(this._type);
        if (isArray(entries)) {
          for (i = 0, n = entries.length; i < n; i += 2) {
            dict[xref.fetchIfRef(entries[i])] = xref.fetchIfRef(entries[i + 1]);
          }
        }
      }
      return dict;
    },

    get: function NameOrNumberTree_get(key) {
      if (!this.root) {
        return null;
      }

      var xref = this.xref;
      var kidsOrEntries = xref.fetchIfRef(this.root);
      var loopCount = 0;
      var MAX_LEVELS = 10;
      var l, r, m;

      // Perform a binary search to quickly find the entry that
      // contains the key we are looking for.
      while (kidsOrEntries.has('Kids')) {
        if (++loopCount > MAX_LEVELS) {
          warn('Search depth limit reached for "' + this._type + '" tree.');
          return null;
        }

        var kids = kidsOrEntries.get('Kids');
        if (!isArray(kids)) {
          return null;
        }

        l = 0;
        r = kids.length - 1;
        while (l <= r) {
          m = (l + r) >> 1;
          var kid = xref.fetchIfRef(kids[m]);
          var limits = kid.get('Limits');

          if (key < xref.fetchIfRef(limits[0])) {
            r = m - 1;
          } else if (key > xref.fetchIfRef(limits[1])) {
            l = m + 1;
          } else {
            kidsOrEntries = xref.fetchIfRef(kids[m]);
            break;
          }
        }
        if (l > r) {
          return null;
        }
      }

      // If we get here, then we have found the right entry. Now go through the
      // entries in the dictionary until we find the key we're looking for.
      var entries = kidsOrEntries.get(this._type);
      if (isArray(entries)) {
        // Perform a binary search to reduce the lookup time.
        l = 0;
        r = entries.length - 2;
        while (l <= r) {
          // Check only even indices (0, 2, 4, ...) because the
          // odd indices contain the actual data.
          m = (l + r) & ~1;
          var currentKey = xref.fetchIfRef(entries[m]);
          if (key < currentKey) {
            r = m - 2;
          } else if (key > currentKey) {
            l = m + 2;
          } else {
            return xref.fetchIfRef(entries[m + 1]);
          }
        }
      }
      return null;
    },
  };
  return NameOrNumberTree;
})();

var NameTree = (function NameTreeClosure() {
  function NameTree(root, xref) {
    this.root = root;
    this.xref = xref;
    this._type = 'Names';
  }

  Util.inherit(NameTree, NameOrNumberTree, {});

  return NameTree;
})();

var NumberTree = (function NumberTreeClosure() {
  function NumberTree(root, xref) {
    this.root = root;
    this.xref = xref;
    this._type = 'Nums';
  }

  Util.inherit(NumberTree, NameOrNumberTree, {});

  return NumberTree;
})();

/**
 * "A PDF file can refer to the contents of another file by using a File
 * Specification (PDF 1.1)", see the spec (7.11) for more details.
 * NOTE: Only embedded files are supported (as part of the attachments support)
 * TODO: support the 'URL' file system (with caching if !/V), portable
 * collections attributes and related files (/RF)
 */
var FileSpec = (function FileSpecClosure() {
  function FileSpec(root, xref) {
    if (!root || !isDict(root)) {
      return;
    }
    this.xref = xref;
    this.root = root;
    if (root.has('FS')) {
      this.fs = root.get('FS');
    }
    this.description = root.has('Desc') ?
                         stringToPDFString(root.get('Desc')) :
                         '';
    if (root.has('RF')) {
      warn('Related file specifications are not supported');
    }
    this.contentAvailable = true;
    if (!root.has('EF')) {
      this.contentAvailable = false;
      warn('Non-embedded file specifications are not supported');
    }
  }

  function pickPlatformItem(dict) {
    // Look for the filename in this order:
    // UF, F, Unix, Mac, DOS
    if (dict.has('UF')) {
      return dict.get('UF');
    } else if (dict.has('F')) {
      return dict.get('F');
    } else if (dict.has('Unix')) {
      return dict.get('Unix');
    } else if (dict.has('Mac')) {
      return dict.get('Mac');
    } else if (dict.has('DOS')) {
      return dict.get('DOS');
    }
    return null;
  }

  FileSpec.prototype = {
    get filename() {
      if (!this._filename && this.root) {
        var filename = pickPlatformItem(this.root) || 'unnamed';
        this._filename = stringToPDFString(filename).
          replace(/\\\\/g, '\\').
          replace(/\\\//g, '/').
          replace(/\\/g, '/');
      }
      return this._filename;
    },
    get content() {
      if (!this.contentAvailable) {
        return null;
      }
      if (!this.contentRef && this.root) {
        this.contentRef = pickPlatformItem(this.root.get('EF'));
      }
      var content = null;
      if (this.contentRef) {
        var xref = this.xref;
        var fileObj = xref.fetchIfRef(this.contentRef);
        if (fileObj && isStream(fileObj)) {
          content = fileObj.getBytes();
        } else {
          warn('Embedded file specification points to non-existing/invalid ' +
            'content');
        }
      } else {
        warn('Embedded file specification does not have a content');
      }
      return content;
    },
    get serializable() {
      return {
        filename: this.filename,
        content: this.content,
      };
    },
  };
  return FileSpec;
})();

/**
 * A helper for loading missing data in object graphs. It traverses the graph
 * depth first and queues up any objects that have missing data. Once it has
 * has traversed as many objects that are available it attempts to bundle the
 * missing data requests and then resume from the nodes that weren't ready.
 *
 * NOTE: It provides protection from circular references by keeping track of
 * of loaded references. However, you must be careful not to load any graphs
 * that have references to the catalog or other pages since that will cause the
 * entire PDF document object graph to be traversed.
 */
var ObjectLoader = (function() {
  function mayHaveChildren(value) {
    return isRef(value) || isDict(value) || isArray(value) || isStream(value);
  }

  function addChildren(node, nodesToVisit) {
    var value;
    if (isDict(node) || isStream(node)) {
      var map;
      if (isDict(node)) {
        map = node.map;
      } else {
        map = node.dict.map;
      }
      for (var key in map) {
        value = map[key];
        if (mayHaveChildren(value)) {
          nodesToVisit.push(value);
        }
      }
    } else if (isArray(node)) {
      for (var i = 0, ii = node.length; i < ii; i++) {
        value = node[i];
        if (mayHaveChildren(value)) {
          nodesToVisit.push(value);
        }
      }
    }
  }

  function ObjectLoader(obj, keys, xref) {
    this.obj = obj;
    this.keys = keys;
    this.xref = xref;
    this.refSet = null;
    this.capability = null;
  }

  ObjectLoader.prototype = {
    load: function ObjectLoader_load() {
      var keys = this.keys;
      this.capability = createPromiseCapability();
      // Don't walk the graph if all the data is already loaded.
      if (!(this.xref.stream instanceof ChunkedStream) ||
          this.xref.stream.getMissingChunks().length === 0) {
        this.capability.resolve();
        return this.capability.promise;
      }

      this.refSet = new RefSet();
      // Setup the initial nodes to visit.
      var nodesToVisit = [];
      for (var i = 0; i < keys.length; i++) {
        nodesToVisit.push(this.obj[keys[i]]);
      }

      this._walk(nodesToVisit);
      return this.capability.promise;
    },

    _walk: function ObjectLoader_walk(nodesToVisit) {
      var nodesToRevisit = [];
      var pendingRequests = [];
      // DFS walk of the object graph.
      while (nodesToVisit.length) {
        var currentNode = nodesToVisit.pop();

        // Only references or chunked streams can cause missing data exceptions.
        if (isRef(currentNode)) {
          // Skip nodes that have already been visited.
          if (this.refSet.has(currentNode)) {
            continue;
          }
          try {
            var ref = currentNode;
            this.refSet.put(ref);
            currentNode = this.xref.fetch(currentNode);
          } catch (e) {
            if (!(e instanceof MissingDataException)) {
              throw e;
            }
            nodesToRevisit.push(currentNode);
            pendingRequests.push({ begin: e.begin, end: e.end, });
          }
        }
        if (currentNode && currentNode.getBaseStreams) {
          var baseStreams = currentNode.getBaseStreams();
          var foundMissingData = false;
          for (var i = 0; i < baseStreams.length; i++) {
            var stream = baseStreams[i];
            if (stream.getMissingChunks && stream.getMissingChunks().length) {
              foundMissingData = true;
              pendingRequests.push({
                begin: stream.start,
                end: stream.end,
              });
            }
          }
          if (foundMissingData) {
            nodesToRevisit.push(currentNode);
          }
        }

        addChildren(currentNode, nodesToVisit);
      }

      if (pendingRequests.length) {
        this.xref.stream.manager.requestRanges(pendingRequests).then(() => {
          nodesToVisit = nodesToRevisit;
          for (var i = 0; i < nodesToRevisit.length; i++) {
            var node = nodesToRevisit[i];
            // Remove any reference nodes from the currrent refset so they
            // aren't skipped when we revist them.
            if (isRef(node)) {
              this.refSet.remove(node);
            }
          }
          this._walk(nodesToVisit);
        }, this.capability.reject);
        return;
      }
      // Everything is loaded.
      this.refSet = null;
      this.capability.resolve();
    },
  };

  return ObjectLoader;
})();

export {
  Catalog,
  ObjectLoader,
  XRef,
  FileSpec,
};