core_utils.js

/* Copyright 2019 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,
  BaseException,
  objectSize,
  stringToPDFString,
  warn,
} from "../shared/util.js";
import { Dict, isName, isRef, isStream, RefSet } from "./primitives.js";

function getLookupTableFactory(initializer) {
  let lookup;
  return function () {
    if (initializer) {
      lookup = Object.create(null);
      initializer(lookup);
      initializer = null;
    }
    return lookup;
  };
}

function getArrayLookupTableFactory(initializer) {
  let lookup;
  return function () {
    if (initializer) {
      let arr = initializer();
      initializer = null;
      lookup = Object.create(null);
      for (let i = 0, ii = arr.length; i < ii; i += 2) {
        lookup[arr[i]] = arr[i + 1];
      }
      arr = null;
    }
    return lookup;
  };
}

class MissingDataException extends BaseException {
  constructor(begin, end) {
    super(`Missing data [${begin}, ${end})`);
    this.begin = begin;
    this.end = end;
  }
}

class XRefEntryException extends BaseException {}

class XRefParseException extends BaseException {}

/**
 * Get the value of an inheritable property.
 *
 * If the PDF specification explicitly lists a property in a dictionary as
 * inheritable, then the value of the property may be present in the dictionary
 * itself or in one or more parents of the dictionary.
 *
 * If the key is not found in the tree, `undefined` is returned. Otherwise,
 * the value for the key is returned or, if `stopWhenFound` is `false`, a list
 * of values is returned.
 *
 * @param {Dict} dict - Dictionary from where to start the traversal.
 * @param {string} key - The key of the property to find the value for.
 * @param {boolean} getArray - Whether or not the value should be fetched as an
 *   array. The default value is `false`.
 * @param {boolean} stopWhenFound - Whether or not to stop the traversal when
 *   the key is found. If set to `false`, we always walk up the entire parent
 *   chain, for example to be able to find `\Resources` placed on multiple
 *   levels of the tree. The default value is `true`.
 */
function getInheritableProperty({
  dict,
  key,
  getArray = false,
  stopWhenFound = true,
}) {
  let values;
  const visited = new RefSet();

  while (dict instanceof Dict && !(dict.objId && visited.has(dict.objId))) {
    if (dict.objId) {
      visited.put(dict.objId);
    }
    const value = getArray ? dict.getArray(key) : dict.get(key);
    if (value !== undefined) {
      if (stopWhenFound) {
        return value;
      }
      if (!values) {
        values = [];
      }
      values.push(value);
    }
    dict = dict.get("Parent");
  }
  return values;
}

// prettier-ignore
const ROMAN_NUMBER_MAP = [
  "", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM",
  "", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC",
  "", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"
];

/**
 * Converts positive integers to (upper case) Roman numerals.
 * @param {number} number - The number that should be converted.
 * @param {boolean} lowerCase - Indicates if the result should be converted
 *   to lower case letters. The default value is `false`.
 * @returns {string} The resulting Roman number.
 */
function toRomanNumerals(number, lowerCase = false) {
  assert(
    Number.isInteger(number) && number > 0,
    "The number should be a positive integer."
  );
  const romanBuf = [];
  let pos;
  // Thousands
  while (number >= 1000) {
    number -= 1000;
    romanBuf.push("M");
  }
  // Hundreds
  pos = (number / 100) | 0;
  number %= 100;
  romanBuf.push(ROMAN_NUMBER_MAP[pos]);
  // Tens
  pos = (number / 10) | 0;
  number %= 10;
  romanBuf.push(ROMAN_NUMBER_MAP[10 + pos]);
  // Ones
  romanBuf.push(ROMAN_NUMBER_MAP[20 + number]);

  const romanStr = romanBuf.join("");
  return lowerCase ? romanStr.toLowerCase() : romanStr;
}

// Calculate the base 2 logarithm of the number `x`. This differs from the
// native function in the sense that it returns the ceiling value and that it
// returns 0 instead of `Infinity`/`NaN` for `x` values smaller than/equal to 0.
function log2(x) {
  if (x <= 0) {
    return 0;
  }
  return Math.ceil(Math.log2(x));
}

function readInt8(data, offset) {
  return (data[offset] << 24) >> 24;
}

function readUint16(data, offset) {
  return (data[offset] << 8) | data[offset + 1];
}

function readUint32(data, offset) {
  return (
    ((data[offset] << 24) |
      (data[offset + 1] << 16) |
      (data[offset + 2] << 8) |
      data[offset + 3]) >>>
    0
  );
}

// Checks if ch is one of the following characters: SPACE, TAB, CR or LF.
function isWhiteSpace(ch) {
  return ch === 0x20 || ch === 0x09 || ch === 0x0d || ch === 0x0a;
}

/**
 * AcroForm field names use an array like notation to refer to
 * repeated XFA elements e.g. foo.bar[nnn].
 * see: XFA Spec Chapter 3 - Repeated Elements
 *
 * @param {string} path - XFA path name.
 * @returns {Array} - Array of Objects with the name and pos of
 * each part of the path.
 */
function parseXFAPath(path) {
  const positionPattern = /(.+)\[([0-9]+)\]$/;
  return path.split(".").map(component => {
    const m = component.match(positionPattern);
    if (m) {
      return { name: m[1], pos: parseInt(m[2], 10) };
    }
    return { name: component, pos: 0 };
  });
}

function escapePDFName(str) {
  const buffer = [];
  let start = 0;
  for (let i = 0, ii = str.length; i < ii; i++) {
    const char = str.charCodeAt(i);
    // Whitespace or delimiters aren't regular chars, so escape them.
    if (
      char < 0x21 ||
      char > 0x7e ||
      char === 0x23 /* # */ ||
      char === 0x28 /* ( */ ||
      char === 0x29 /* ) */ ||
      char === 0x3c /* < */ ||
      char === 0x3e /* > */ ||
      char === 0x5b /* [ */ ||
      char === 0x5d /* ] */ ||
      char === 0x7b /* { */ ||
      char === 0x7d /* } */ ||
      char === 0x2f /* / */ ||
      char === 0x25 /* % */
    ) {
      if (start < i) {
        buffer.push(str.substring(start, i));
      }
      buffer.push(`#${char.toString(16)}`);
      start = i + 1;
    }
  }

  if (buffer.length === 0) {
    return str;
  }

  if (start < str.length) {
    buffer.push(str.substring(start, str.length));
  }

  return buffer.join("");
}

function _collectJS(entry, xref, list, parents) {
  if (!entry) {
    return;
  }

  let parent = null;
  if (isRef(entry)) {
    if (parents.has(entry)) {
      // If we've already found entry then we've a cycle.
      return;
    }
    parent = entry;
    parents.put(parent);
    entry = xref.fetch(entry);
  }
  if (Array.isArray(entry)) {
    for (const element of entry) {
      _collectJS(element, xref, list, parents);
    }
  } else if (entry instanceof Dict) {
    if (isName(entry.get("S"), "JavaScript") && entry.has("JS")) {
      const js = entry.get("JS");
      let code;
      if (isStream(js)) {
        code = js.getString();
      } else {
        code = js;
      }
      code = stringToPDFString(code);
      if (code) {
        list.push(code);
      }
    }
    _collectJS(entry.getRaw("Next"), xref, list, parents);
  }

  if (parent) {
    parents.remove(parent);
  }
}

function collectActions(xref, dict, eventType) {
  const actions = Object.create(null);
  const additionalActionsDicts = getInheritableProperty({
    dict,
    key: "AA",
    stopWhenFound: false,
  });
  if (additionalActionsDicts) {
    // additionalActionsDicts contains dicts from ancestors
    // as they're found in the tree from bottom to top.
    // So the dicts are visited in reverse order to guarantee
    // that actions from elder ancestors will be overwritten
    // by ones from younger ancestors.
    for (let i = additionalActionsDicts.length - 1; i >= 0; i--) {
      const additionalActions = additionalActionsDicts[i];
      if (!(additionalActions instanceof Dict)) {
        continue;
      }
      for (const key of additionalActions.getKeys()) {
        const action = eventType[key];
        if (!action) {
          continue;
        }
        const actionDict = additionalActions.getRaw(key);
        const parents = new RefSet();
        const list = [];
        _collectJS(actionDict, xref, list, parents);
        if (list.length > 0) {
          actions[action] = list;
        }
      }
    }
  }
  // Collect the Action if any (we may have one on pushbutton).
  if (dict.has("A")) {
    const actionDict = dict.get("A");
    const parents = new RefSet();
    const list = [];
    _collectJS(actionDict, xref, list, parents);
    if (list.length > 0) {
      actions.Action = list;
    }
  }
  return objectSize(actions) > 0 ? actions : null;
}

const XMLEntities = {
  /* < */ 0x3c: "&lt;",
  /* > */ 0x3e: "&gt;",
  /* & */ 0x26: "&amp;",
  /* " */ 0x22: "&quot;",
  /* ' */ 0x27: "&apos;",
};

function encodeToXmlString(str) {
  const buffer = [];
  let start = 0;
  for (let i = 0, ii = str.length; i < ii; i++) {
    const char = str.codePointAt(i);
    if (0x20 <= char && char <= 0x7e) {
      // ascii
      const entity = XMLEntities[char];
      if (entity) {
        if (start < i) {
          buffer.push(str.substring(start, i));
        }
        buffer.push(entity);
        start = i + 1;
      }
    } else {
      if (start < i) {
        buffer.push(str.substring(start, i));
      }
      buffer.push(`&#x${char.toString(16).toUpperCase()};`);
      if (char > 0xd7ff && (char < 0xe000 || char > 0xfffd)) {
        // char is represented by two u16
        i++;
      }
      start = i + 1;
    }
  }

  if (buffer.length === 0) {
    return str;
  }
  if (start < str.length) {
    buffer.push(str.substring(start, str.length));
  }
  return buffer.join("");
}

function validateCSSFont(cssFontInfo) {
  // See https://developer.mozilla.org/en-US/docs/Web/CSS/font-style.
  const DEFAULT_CSS_FONT_OBLIQUE = "14";
  // See https://developer.mozilla.org/en-US/docs/Web/CSS/font-weight.
  const DEFAULT_CSS_FONT_WEIGHT = "400";
  const CSS_FONT_WEIGHT_VALUES = new Set([
    "100",
    "200",
    "300",
    "400",
    "500",
    "600",
    "700",
    "800",
    "900",
    "1000",
    "normal",
    "bold",
    "bolder",
    "lighter",
  ]);

  const { fontFamily, fontWeight, italicAngle } = cssFontInfo;

  // See https://developer.mozilla.org/en-US/docs/Web/CSS/string.
  if (/^".*"$/.test(fontFamily)) {
    if (/[^\\]"/.test(fontFamily.slice(1, fontFamily.length - 1))) {
      warn(`XFA - FontFamily contains some unescaped ": ${fontFamily}.`);
      return false;
    }
  } else if (/^'.*'$/.test(fontFamily)) {
    if (/[^\\]'/.test(fontFamily.slice(1, fontFamily.length - 1))) {
      warn(`XFA - FontFamily contains some unescaped ': ${fontFamily}.`);
      return false;
    }
  } else {
    // See https://developer.mozilla.org/en-US/docs/Web/CSS/custom-ident.
    for (const ident of fontFamily.split(/[ \t]+/)) {
      if (
        /^([0-9]|(-([0-9]|-)))/.test(ident) ||
        !/^[a-zA-Z0-9\-_\\]+$/.test(ident)
      ) {
        warn(
          `XFA - FontFamily contains some invalid <custom-ident>: ${fontFamily}.`
        );
        return false;
      }
    }
  }

  const weight = fontWeight ? fontWeight.toString() : "";
  cssFontInfo.fontWeight = CSS_FONT_WEIGHT_VALUES.has(weight)
    ? weight
    : DEFAULT_CSS_FONT_WEIGHT;

  const angle = parseFloat(italicAngle);
  cssFontInfo.italicAngle =
    isNaN(angle) || angle < -90 || angle > 90
      ? DEFAULT_CSS_FONT_OBLIQUE
      : italicAngle.toString();

  return true;
}

export {
  collectActions,
  encodeToXmlString,
  escapePDFName,
  getArrayLookupTableFactory,
  getInheritableProperty,
  getLookupTableFactory,
  isWhiteSpace,
  log2,
  MissingDataException,
  parseXFAPath,
  readInt8,
  readUint16,
  readUint32,
  toRomanNumerals,
  validateCSSFont,
  XRefEntryException,
  XRefParseException,
};