pdf.js/src/core/document.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.
 */
/* eslint no-var: error */

import {
  assert, FormatError, getInheritableProperty, info, isArrayBuffer, isBool,
  isNum, isSpace, isString, MissingDataException, OPS, shadow, stringToBytes,
  stringToPDFString, Util, warn, XRefEntryException, XRefParseException
} from '../shared/util';
import { Catalog, ObjectLoader, XRef } from './obj';
import { Dict, isDict, isName, isStream, Ref } from './primitives';
import { NullStream, Stream, StreamsSequenceStream } from './stream';
import { AnnotationFactory } from './annotation';
import { calculateMD5 } from './crypto';
import { Linearization } from './parser';
import { OperatorList } from './operator_list';
import { PartialEvaluator } from './evaluator';
import { PDFFunctionFactory } from './function';

const DEFAULT_USER_UNIT = 1.0;
const LETTER_SIZE_MEDIABOX = [0, 0, 612, 792];

function isAnnotationRenderable(annotation, intent) {
  return (intent === 'display' && annotation.viewable) ||
         (intent === 'print' && annotation.printable);
}

class Page {
  constructor({ pdfManager, xref, pageIndex, pageDict, ref, fontCache,
                builtInCMapCache, pdfFunctionFactory, }) {
    this.pdfManager = pdfManager;
    this.pageIndex = pageIndex;
    this.pageDict = pageDict;
    this.xref = xref;
    this.ref = ref;
    this.fontCache = fontCache;
    this.builtInCMapCache = builtInCMapCache;
    this.pdfFunctionFactory = pdfFunctionFactory;
    this.evaluatorOptions = pdfManager.evaluatorOptions;
    this.resourcesPromise = null;

    const uniquePrefix = `p${this.pageIndex}_`;
    const idCounters = {
      obj: 0,
    };
    this.idFactory = {
      createObjId() {
        return uniquePrefix + (++idCounters.obj);
      },
    };
  }

  /**
   * @private
   */
  _getInheritableProperty(key, getArray = false) {
    const value = getInheritableProperty({ dict: this.pageDict, key, getArray,
                                           stopWhenFound: false, });
    if (!Array.isArray(value)) {
      return value;
    }
    if (value.length === 1 || !isDict(value[0])) {
      return value[0];
    }
    return Dict.merge(this.xref, value);
  }

  get content() {
    return this.pageDict.get('Contents');
  }

  get resources() {
    // For robustness: The spec states that a \Resources entry has to be
    // present, but can be empty. Some documents still omit it; in this case
    // we return an empty dictionary.
    return shadow(this, 'resources',
                  this._getInheritableProperty('Resources') || Dict.empty);
  }

  get mediaBox() {
    const mediaBox = this._getInheritableProperty('MediaBox',
                                                  /* getArray = */ true);
    // Reset invalid media box to letter size.
    if (!Array.isArray(mediaBox) || mediaBox.length !== 4) {
      return shadow(this, 'mediaBox', LETTER_SIZE_MEDIABOX);
    }
    return shadow(this, 'mediaBox', mediaBox);
  }

  get cropBox() {
    const cropBox = this._getInheritableProperty('CropBox',
                                                 /* getArray = */ true);
    // Reset invalid crop box to media box.
    if (!Array.isArray(cropBox) || cropBox.length !== 4) {
      return shadow(this, 'cropBox', this.mediaBox);
    }
    return shadow(this, 'cropBox', cropBox);
  }

  get userUnit() {
    let obj = this.pageDict.get('UserUnit');
    if (!isNum(obj) || obj <= 0) {
      obj = DEFAULT_USER_UNIT;
    }
    return shadow(this, 'userUnit', obj);
  }

  get view() {
    // From the spec, 6th ed., p.963:
    // "The crop, bleed, trim, and art boxes should not ordinarily
    // extend beyond the boundaries of the media box. If they do, they are
    // effectively reduced to their intersection with the media box."
    const mediaBox = this.mediaBox, cropBox = this.cropBox;
    if (mediaBox === cropBox) {
      return shadow(this, 'view', mediaBox);
    }

    const intersection = Util.intersect(cropBox, mediaBox);
    return shadow(this, 'view', intersection || mediaBox);
  }

  get rotate() {
    let rotate = this._getInheritableProperty('Rotate') || 0;

    // Normalize rotation so it's a multiple of 90 and between 0 and 270.
    if (rotate % 90 !== 0) {
      rotate = 0;
    } else if (rotate >= 360) {
      rotate = rotate % 360;
    } else if (rotate < 0) {
      // The spec doesn't cover negatives. Assume it's counterclockwise
      // rotation. The following is the other implementation of modulo.
      rotate = ((rotate % 360) + 360) % 360;
    }
    return shadow(this, 'rotate', rotate);
  }

  getContentStream() {
    const content = this.content;
    let stream;

    if (Array.isArray(content)) {
      // Fetching the individual streams from the array.
      const xref = this.xref;
      const streams = [];
      for (const stream of content) {
        streams.push(xref.fetchIfRef(stream));
      }
      stream = new StreamsSequenceStream(streams);
    } else if (isStream(content)) {
      stream = content;
    } else {
      // Replace non-existent page content with empty content.
      stream = new NullStream();
    }
    return stream;
  }

  loadResources(keys) {
    if (!this.resourcesPromise) {
      // TODO: add async `_getInheritableProperty` and remove this.
      this.resourcesPromise = this.pdfManager.ensure(this, 'resources');
    }
    return this.resourcesPromise.then(() => {
      const objectLoader = new ObjectLoader(this.resources, keys, this.xref);
      return objectLoader.load();
    });
  }

  getOperatorList({ handler, task, intent, renderInteractiveForms, }) {
    const contentStreamPromise = this.pdfManager.ensure(this,
                                                        'getContentStream');
    const resourcesPromise = this.loadResources([
      'ExtGState',
      'ColorSpace',
      'Pattern',
      'Shading',
      'XObject',
      'Font',
    ]);

    const partialEvaluator = new PartialEvaluator({
      pdfManager: this.pdfManager,
      xref: this.xref,
      handler,
      pageIndex: this.pageIndex,
      idFactory: this.idFactory,
      fontCache: this.fontCache,
      builtInCMapCache: this.builtInCMapCache,
      options: this.evaluatorOptions,
      pdfFunctionFactory: this.pdfFunctionFactory,
    });

    const dataPromises = Promise.all([contentStreamPromise, resourcesPromise]);
    const pageListPromise = dataPromises.then(([contentStream]) => {
      const opList = new OperatorList(intent, handler, this.pageIndex);

      handler.send('StartRenderPage', {
        transparency: partialEvaluator.hasBlendModes(this.resources),
        pageIndex: this.pageIndex,
        intent,
      });

      return partialEvaluator.getOperatorList({
        stream: contentStream,
        task,
        resources: this.resources,
        operatorList: opList,
      }).then(function() {
        return opList;
      });
    });

    // Fetch the page's annotations and add their operator lists to the
    // page's operator list to render them.
    return Promise.all([pageListPromise, this._parsedAnnotations]).then(
        function([pageOpList, annotations]) {
      if (annotations.length === 0) {
        pageOpList.flush(true);
        return pageOpList;
      }

      // Collect the operator list promises for the annotations. Each promise
      // is resolved with the complete operator list for a single annotation.
      const opListPromises = [];
      for (const annotation of annotations) {
        if (isAnnotationRenderable(annotation, intent)) {
          opListPromises.push(annotation.getOperatorList(
            partialEvaluator, task, renderInteractiveForms));
        }
      }

      return Promise.all(opListPromises).then(function(opLists) {
        pageOpList.addOp(OPS.beginAnnotations, []);
        for (const opList of opLists) {
          pageOpList.addOpList(opList);
        }
        pageOpList.addOp(OPS.endAnnotations, []);
        pageOpList.flush(true);
        return pageOpList;
      });
    });
  }

  extractTextContent({ handler, task, normalizeWhitespace, sink,
                       combineTextItems, }) {
    const contentStreamPromise = this.pdfManager.ensure(this,
                                                        'getContentStream');
    const resourcesPromise = this.loadResources([
      'ExtGState',
      'XObject',
      'Font',
    ]);

    const dataPromises = Promise.all([contentStreamPromise, resourcesPromise]);
    return dataPromises.then(([contentStream]) => {
      const partialEvaluator = new PartialEvaluator({
        pdfManager: this.pdfManager,
        xref: this.xref,
        handler,
        pageIndex: this.pageIndex,
        idFactory: this.idFactory,
        fontCache: this.fontCache,
        builtInCMapCache: this.builtInCMapCache,
        options: this.evaluatorOptions,
        pdfFunctionFactory: this.pdfFunctionFactory,
      });

      return partialEvaluator.getTextContent({
        stream: contentStream,
        task,
        resources: this.resources,
        normalizeWhitespace,
        combineTextItems,
        sink,
      });
    });
  }

  getAnnotationsData(intent) {
    return this._parsedAnnotations.then(function(annotations) {
      const annotationsData = [];
      for (let i = 0, ii = annotations.length; i < ii; i++) {
        if (!intent || isAnnotationRenderable(annotations[i], intent)) {
          annotationsData.push(annotations[i].data);
        }
      }
      return annotationsData;
    });
  }

  get annotations() {
    return shadow(this, 'annotations',
                  this._getInheritableProperty('Annots') || []);
  }

  get _parsedAnnotations() {
    const parsedAnnotations =
      this.pdfManager.ensure(this, 'annotations').then(() => {
        const annotationRefs = this.annotations;
        const annotationPromises = [];
        for (let i = 0, ii = annotationRefs.length; i < ii; i++) {
          annotationPromises.push(AnnotationFactory.create(
            this.xref, annotationRefs[i], this.pdfManager, this.idFactory));
        }

        return Promise.all(annotationPromises).then(function(annotations) {
          return annotations.filter(function isDefined(annotation) {
            return !!annotation;
          });
        }, function(reason) {
          warn(`_parsedAnnotations: "${reason}".`);
          return [];
        });
      });

    return shadow(this, '_parsedAnnotations', parsedAnnotations);
  }
}

const FINGERPRINT_FIRST_BYTES = 1024;
const EMPTY_FINGERPRINT = '\x00\x00\x00\x00\x00\x00\x00' +
                          '\x00\x00\x00\x00\x00\x00\x00\x00\x00';

function find(stream, needle, limit, backwards) {
  const pos = stream.pos;
  const end = stream.end;
  if (pos + limit > end) {
    limit = end - pos;
  }

  const strBuf = [];
  for (let i = 0; i < limit; ++i) {
    strBuf.push(String.fromCharCode(stream.getByte()));
  }
  const str = strBuf.join('');

  stream.pos = pos;
  const index = backwards ? str.lastIndexOf(needle) : str.indexOf(needle);
  if (index === -1) {
    return false;
  }
  stream.pos += index;
  return true;
}

/**
 * The `PDFDocument` class holds all the data of the PDF file. There exists
 * one `PDFDocument` object on the main thread and one object for each worker.
 * If no worker support is enabled, two `PDFDocument` objects are created on
 * the main thread.
 */
class PDFDocument {
  constructor(pdfManager, arg) {
    let stream;
    if (isStream(arg)) {
      stream = arg;
    } else if (isArrayBuffer(arg)) {
      stream = new Stream(arg);
    } else {
      throw new Error('PDFDocument: Unknown argument type');
    }
    if (stream.length <= 0) {
      throw new Error('PDFDocument: Stream must have data');
    }

    this.pdfManager = pdfManager;
    this.stream = stream;
    this.xref = new XRef(stream, pdfManager);

    this.pdfFunctionFactory = new PDFFunctionFactory({
      xref: this.xref,
      isEvalSupported: pdfManager.evaluatorOptions.isEvalSupported,
    });
    this._pagePromises = [];
  }

  parse(recoveryMode) {
    this.setup(recoveryMode);

    const version = this.catalog.catDict.get('Version');
    if (isName(version)) {
      this.pdfFormatVersion = version.name;
    }

    // Check if AcroForms are present in the document.
    try {
      this.acroForm = this.catalog.catDict.get('AcroForm');
      if (this.acroForm) {
        this.xfa = this.acroForm.get('XFA');
        const fields = this.acroForm.get('Fields');
        if ((!fields || !Array.isArray(fields) || fields.length === 0) &&
            !this.xfa) {
          this.acroForm = null; // No fields and no XFA, so it's not a form.
        }
      }
    } catch (ex) {
      if (ex instanceof MissingDataException) {
        throw ex;
      }
      info('Cannot fetch AcroForm entry; assuming no AcroForms are present');
      this.acroForm = null;
    }
  }

  get linearization() {
    let linearization = null;
    try {
      linearization = Linearization.create(this.stream);
    } catch (err) {
      if (err instanceof MissingDataException) {
        throw err;
      }
      info(err);
    }
    return shadow(this, 'linearization', linearization);
  }

  get startXRef() {
    const stream = this.stream;
    let startXRef = 0;

    if (this.linearization) {
      // Find the end of the first object.
      stream.reset();
      if (find(stream, 'endobj', 1024)) {
        startXRef = stream.pos + 6;
      }
    } else {
      // Find `startxref` by checking backwards from the end of the file.
      const step = 1024;
      const startXRefLength = 'startxref'.length;
      let found = false, pos = stream.end;

      while (!found && pos > 0) {
        pos -= step - startXRefLength;
        if (pos < 0) {
          pos = 0;
        }
        stream.pos = pos;
        found = find(stream, 'startxref', step, true);
      }

      if (found) {
        stream.skip(9);
        let ch;
        do {
          ch = stream.getByte();
        } while (isSpace(ch));
        let str = '';
        while (ch >= 0x20 && ch <= 0x39) { // < '9'
          str += String.fromCharCode(ch);
          ch = stream.getByte();
        }
        startXRef = parseInt(str, 10);
        if (isNaN(startXRef)) {
          startXRef = 0;
        }
      }
    }
    return shadow(this, 'startXRef', startXRef);
  }

  // Find the header, get the PDF format version and setup the
  // stream to start from the header.
  checkHeader() {
    const stream = this.stream;
    stream.reset();

    if (!find(stream, '%PDF-', 1024)) {
      // May not be a PDF file, but don't throw an error and let
      // parsing continue.
      return;
    }
    stream.moveStart();

    // Read the PDF format version.
    const MAX_PDF_VERSION_LENGTH = 12;
    let version = '', ch;
    while ((ch = stream.getByte()) > 0x20) { // Space
      if (version.length >= MAX_PDF_VERSION_LENGTH) {
        break;
      }
      version += String.fromCharCode(ch);
    }
    if (!this.pdfFormatVersion) {
      // Remove the "%PDF-" prefix.
      this.pdfFormatVersion = version.substring(5);
    }
  }

  parseStartXRef() {
    this.xref.setStartXRef(this.startXRef);
  }

  setup(recoveryMode) {
    this.xref.parse(recoveryMode);
    this.catalog = new Catalog(this.pdfManager, this.xref);
  }

  get numPages() {
    const linearization = this.linearization;
    const num = linearization ? linearization.numPages : this.catalog.numPages;
    return shadow(this, 'numPages', num);
  }

  get documentInfo() {
    const DocumentInfoValidators = {
      Title: isString,
      Author: isString,
      Subject: isString,
      Keywords: isString,
      Creator: isString,
      Producer: isString,
      CreationDate: isString,
      ModDate: isString,
      Trapped: isName,
    };

    const docInfo = {
      PDFFormatVersion: this.pdfFormatVersion,
      IsLinearized: !!this.linearization,
      IsAcroFormPresent: !!this.acroForm,
      IsXFAPresent: !!this.xfa,
    };

    let infoDict;
    try {
      infoDict = this.xref.trailer.get('Info');
    } catch (err) {
      if (err instanceof MissingDataException) {
        throw err;
      }
      info('The document information dictionary is invalid.');
    }

    if (isDict(infoDict)) {
      // Fill the document info with valid entries from the specification,
      // as well as any existing well-formed custom entries.
      for (const key of infoDict.getKeys()) {
        const value = infoDict.get(key);

        if (DocumentInfoValidators[key]) {
          // Make sure the (standard) value conforms to the specification.
          if (DocumentInfoValidators[key](value)) {
            docInfo[key] = (typeof value !== 'string' ?
                            value : stringToPDFString(value));
          } else {
            info(`Bad value in document info for "${key}".`);
          }
        } else if (typeof key === 'string') {
          // For custom values, only accept white-listed types to prevent
          // errors that would occur when trying to send non-serializable
          // objects to the main-thread (for example `Dict` or `Stream`).
          let customValue;
          if (isString(value)) {
            customValue = stringToPDFString(value);
          } else if (isName(value) || isNum(value) || isBool(value)) {
            customValue = value;
          } else {
            info(`Unsupported value in document info for (custom) "${key}".`);
            continue;
          }

          if (!docInfo['Custom']) {
            docInfo['Custom'] = Object.create(null);
          }
          docInfo['Custom'][key] = customValue;
        }
      }
    }
    return shadow(this, 'documentInfo', docInfo);
  }

  get fingerprint() {
    let hash;
    const idArray = this.xref.trailer.get('ID');
    if (Array.isArray(idArray) && idArray[0] && isString(idArray[0]) &&
        idArray[0] !== EMPTY_FINGERPRINT) {
      hash = stringToBytes(idArray[0]);
    } else {
      if (this.stream.ensureRange) {
        this.stream.ensureRange(0,
          Math.min(FINGERPRINT_FIRST_BYTES, this.stream.end));
      }
      hash = calculateMD5(this.stream.bytes.subarray(0,
        FINGERPRINT_FIRST_BYTES), 0, FINGERPRINT_FIRST_BYTES);
    }

    let fingerprint = '';
    for (let i = 0, ii = hash.length; i < ii; i++) {
      const hex = hash[i].toString(16);
      fingerprint += (hex.length === 1 ? '0' + hex : hex);
    }
    return shadow(this, 'fingerprint', fingerprint);
  }

  _getLinearizationPage(pageIndex) {
    const { catalog, linearization, } = this;
    assert(linearization && linearization.pageFirst === pageIndex);

    const ref = new Ref(linearization.objectNumberFirst, 0);
    return this.xref.fetchAsync(ref).then((obj) => {
      // Ensure that the object that was found is actually a Page dictionary.
      if (isDict(obj, 'Page') ||
          (isDict(obj) && !obj.has('Type') && obj.has('Contents'))) {
        if (ref && !catalog.pageKidsCountCache.has(ref)) {
          catalog.pageKidsCountCache.put(ref, 1); // Cache the Page reference.
        }
        return [obj, ref];
      }
      throw new FormatError('The Linearization dictionary doesn\'t point ' +
                            'to a valid Page dictionary.');
    }).catch((reason) => {
      info(reason);
      return catalog.getPageDict(pageIndex);
    });
  }

  getPage(pageIndex) {
    if (this._pagePromises[pageIndex] !== undefined) {
      return this._pagePromises[pageIndex];
    }
    const { catalog, linearization, } = this;

    const promise = (linearization && linearization.pageFirst === pageIndex) ?
      this._getLinearizationPage(pageIndex) : catalog.getPageDict(pageIndex);

    return this._pagePromises[pageIndex] = promise.then(([pageDict, ref]) => {
      return new Page({
        pdfManager: this.pdfManager,
        xref: this.xref,
        pageIndex,
        pageDict,
        ref,
        fontCache: catalog.fontCache,
        builtInCMapCache: catalog.builtInCMapCache,
        pdfFunctionFactory: this.pdfFunctionFactory,
      });
    });
  }

  checkFirstPage() {
    return this.getPage(0).catch((reason) => {
      if (reason instanceof XRefEntryException) {
        // Clear out the various caches to ensure that we haven't stored any
        // inconsistent and/or incorrect state, since that could easily break
        // subsequent `this.getPage` calls.
        this._pagePromises.length = 0;
        this.cleanup();

        throw new XRefParseException();
      }
    });
  }

  fontFallback(id, handler) {
    return this.catalog.fontFallback(id, handler);
  }

  cleanup() {
    return this.catalog.cleanup();
  }
}

export {
  Page,
  PDFDocument,
};