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Edit File: type1_parser.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 { getEncoding } from "./encodings.js";
import { isWhiteSpace } from "./core_utils.js";
import { Stream } from "./stream.js";
import { warn } from "../shared/util.js";

// Hinting is currently disabled due to unknown problems on windows
// in tracemonkey and various other pdfs with type1 fonts.
const HINTING_ENABLED = false;

const COMMAND_MAP = {
  hstem: [1],
  vstem: [3],
  vmoveto: [4],
  rlineto: [5],
  hlineto: [6],
  vlineto: [7],
  rrcurveto: [8],
  callsubr: [10],
  flex: [12, 35],
  drop: [12, 18],
  endchar: [14],
  rmoveto: [21],
  hmoveto: [22],
  vhcurveto: [30],
  hvcurveto: [31],
};

/**
 * CharStrings are encoded following the CharString Encoding sequence
 * describe in Chapter 6 of the "Adobe Type1 Font Format" specification.
 * The value in a byte indicates a command, a number, or subsequent bytes
 * that are to be interpreted in a special way.
 *
 * CharString Number Encoding:
 *  A CharString byte containing the values from 32 through 255 inclusive
 *  indicate an integer. These values are decoded in four ranges.
 *
 * 1. A CharString byte containing a value, v, between 32 and 246 inclusive,
 * indicate the integer v - 139. Thus, the integer values from -107 through
 * 107 inclusive may be encoded in single byte.
 *
 * 2. A CharString byte containing a value, v, between 247 and 250 inclusive,
 * indicates an integer involving the next byte, w, according to the formula:
 * [(v - 247) x 256] + w + 108
 *
 * 3. A CharString byte containing a value, v, between 251 and 254 inclusive,
 * indicates an integer involving the next byte, w, according to the formula:
 * -[(v - 251) * 256] - w - 108
 *
 * 4. A CharString containing the value 255 indicates that the next 4 bytes
 * are a two complement signed integer. The first of these bytes contains the
 * highest order bits, the second byte contains the next higher order bits
 * and the fourth byte contain the lowest order bits.
 *
 *
 * CharString Command Encoding:
 *  CharStrings commands are encoded in 1 or 2 bytes.
 *
 *  Single byte commands are encoded in 1 byte that contains a value between
 *  0 and 31 inclusive.
 *  If a command byte contains the value 12, then the value in the next byte
 *  indicates a command. This "escape" mechanism allows many extra commands
 *  to be encoded and this encoding technique helps to minimize the length of
 *  the charStrings.
 */
class Type1CharString {
  constructor() {
    this.width = 0;
    this.lsb = 0;
    this.flexing = false;
    this.output = [];
    this.stack = [];
  }

convert(encoded, subrs, seacAnalysisEnabled) {
    const count = encoded.length;
    let error = false;
    let wx, sbx, subrNumber;
    for (let i = 0; i < count; i++) {
      let value = encoded[i];
      if (value < 32) {
        if (value === 12) {
          value = (value << 8) + encoded[++i];
        }
        switch (value) {
          case 1: // hstem
            if (!HINTING_ENABLED) {
              this.stack = [];
              break;
            }
            error = this.executeCommand(2, COMMAND_MAP.hstem);
            break;
          case 3: // vstem
            if (!HINTING_ENABLED) {
              this.stack = [];
              break;
            }
            error = this.executeCommand(2, COMMAND_MAP.vstem);
            break;
          case 4: // vmoveto
            if (this.flexing) {
              if (this.stack.length < 1) {
                error = true;
                break;
              }
              // Add the dx for flex and but also swap the values so they are
              // the right order.
              const dy = this.stack.pop();
              this.stack.push(0, dy);
              break;
            }
            error = this.executeCommand(1, COMMAND_MAP.vmoveto);
            break;
          case 5: // rlineto
            error = this.executeCommand(2, COMMAND_MAP.rlineto);
            break;
          case 6: // hlineto
            error = this.executeCommand(1, COMMAND_MAP.hlineto);
            break;
          case 7: // vlineto
            error = this.executeCommand(1, COMMAND_MAP.vlineto);
            break;
          case 8: // rrcurveto
            error = this.executeCommand(6, COMMAND_MAP.rrcurveto);
            break;
          case 9: // closepath
            // closepath is a Type1 command that does not take argument and is
            // useless in Type2 and it can simply be ignored.
            this.stack = [];
            break;
          case 10: // callsubr
            if (this.stack.length < 1) {
              error = true;
              break;
            }
            subrNumber = this.stack.pop();
            if (!subrs[subrNumber]) {
              error = true;
              break;
            }
            error = this.convert(subrs[subrNumber], subrs, seacAnalysisEnabled);
            break;
          case 11: // return
            return error;
          case 13: // hsbw
            if (this.stack.length < 2) {
              error = true;
              break;
            }
            // To convert to type2 we have to move the width value to the
            // first part of the charstring and then use hmoveto with lsb.
            wx = this.stack.pop();
            sbx = this.stack.pop();
            this.lsb = sbx;
            this.width = wx;
            this.stack.push(wx, sbx);
            error = this.executeCommand(2, COMMAND_MAP.hmoveto);
            break;
          case 14: // endchar
            this.output.push(COMMAND_MAP.endchar[0]);
            break;
          case 21: // rmoveto
            if (this.flexing) {
              break;
            }
            error = this.executeCommand(2, COMMAND_MAP.rmoveto);
            break;
          case 22: // hmoveto
            if (this.flexing) {
              // Add the dy for flex.
              this.stack.push(0);
              break;
            }
            error = this.executeCommand(1, COMMAND_MAP.hmoveto);
            break;
          case 30: // vhcurveto
            error = this.executeCommand(4, COMMAND_MAP.vhcurveto);
            break;
          case 31: // hvcurveto
            error = this.executeCommand(4, COMMAND_MAP.hvcurveto);
            break;
          case (12 << 8) + 0: // dotsection
            // dotsection is a Type1 command to specify some hinting feature
            // for dots that do not take a parameter and it can safely be
            // ignored for Type2.
            this.stack = [];
            break;
          case (12 << 8) + 1: // vstem3
            if (!HINTING_ENABLED) {
              this.stack = [];
              break;
            }
            // [vh]stem3 are Type1 only and Type2 supports [vh]stem with
            // multiple parameters, so instead of returning [vh]stem3 take a
            // shortcut and return [vhstem] instead.
            error = this.executeCommand(2, COMMAND_MAP.vstem);
            break;
          case (12 << 8) + 2: // hstem3
            if (!HINTING_ENABLED) {
              this.stack = [];
              break;
            }
            // See vstem3.
            error = this.executeCommand(2, COMMAND_MAP.hstem);
            break;
          case (12 << 8) + 6: // seac
            // seac is like type 2's special endchar but it doesn't use the
            // first argument asb, so remove it.
            if (seacAnalysisEnabled) {
              const asb = this.stack.at(-5);
              this.seac = this.stack.splice(-4, 4);
              this.seac[0] += this.lsb - asb;
              error = this.executeCommand(0, COMMAND_MAP.endchar);
            } else {
              error = this.executeCommand(4, COMMAND_MAP.endchar);
            }
            break;
          case (12 << 8) + 7: // sbw
            if (this.stack.length < 4) {
              error = true;
              break;
            }
            // To convert to type2 we have to move the width value to the
            // first part of the charstring and then use rmoveto with
            // (dx, dy). The height argument will not be used for vmtx and
            // vhea tables reconstruction -- ignoring it.
            this.stack.pop(); // wy
            wx = this.stack.pop();
            const sby = this.stack.pop();
            sbx = this.stack.pop();
            this.lsb = sbx;
            this.width = wx;
            this.stack.push(wx, sbx, sby);
            error = this.executeCommand(3, COMMAND_MAP.rmoveto);
            break;
          case (12 << 8) + 12: // div
            if (this.stack.length < 2) {
              error = true;
              break;
            }
            const num2 = this.stack.pop();
            const num1 = this.stack.pop();
            this.stack.push(num1 / num2);
            break;
          case (12 << 8) + 16: // callothersubr
            if (this.stack.length < 2) {
              error = true;
              break;
            }
            subrNumber = this.stack.pop();
            const numArgs = this.stack.pop();
            if (subrNumber === 0 && numArgs === 3) {
              const flexArgs = this.stack.splice(-17, 17);
              this.stack.push(
                flexArgs[2] + flexArgs[0], // bcp1x + rpx
                flexArgs[3] + flexArgs[1], // bcp1y + rpy
                flexArgs[4], // bcp2x
                flexArgs[5], // bcp2y
                flexArgs[6], // p2x
                flexArgs[7], // p2y
                flexArgs[8], // bcp3x
                flexArgs[9], // bcp3y
                flexArgs[10], // bcp4x
                flexArgs[11], // bcp4y
                flexArgs[12], // p3x
                flexArgs[13], // p3y
                flexArgs[14] // flexDepth
                // 15 = finalx unused by flex
                // 16 = finaly unused by flex
              );
              error = this.executeCommand(13, COMMAND_MAP.flex, true);
              this.flexing = false;
              this.stack.push(flexArgs[15], flexArgs[16]);
            } else if (subrNumber === 1 && numArgs === 0) {
              this.flexing = true;
            }
            break;
          case (12 << 8) + 17: // pop
            // Ignore this since it is only used with othersubr.
            break;
          case (12 << 8) + 33: // setcurrentpoint
            // Ignore for now.
            this.stack = [];
            break;
          default:
            warn('Unknown type 1 charstring command of "' + value + '"');
            break;
        }
        if (error) {
          break;
        }
        continue;
      } else if (value <= 246) {
        value -= 139;
      } else if (value <= 250) {
        value = (value - 247) * 256 + encoded[++i] + 108;
      } else if (value <= 254) {
        value = -((value - 251) * 256) - encoded[++i] - 108;
      } else {
        value =
          ((encoded[++i] & 0xff) << 24) |
          ((encoded[++i] & 0xff) << 16) |
          ((encoded[++i] & 0xff) << 8) |
          ((encoded[++i] & 0xff) << 0);
      }
      this.stack.push(value);
    }
    return error;
  }

executeCommand(howManyArgs, command, keepStack) {
    const stackLength = this.stack.length;
    if (howManyArgs > stackLength) {
      return true;
    }
    const start = stackLength - howManyArgs;
    for (let i = start; i < stackLength; i++) {
      let value = this.stack[i];
      if (Number.isInteger(value)) {
        this.output.push(28, (value >> 8) & 0xff, value & 0xff);
      } else {
        // fixed point
        value = (65536 * value) | 0;
        this.output.push(
          255,
          (value >> 24) & 0xff,
          (value >> 16) & 0xff,
          (value >> 8) & 0xff,
          value & 0xff
        );
      }
    }
    this.output.push(...command);
    if (keepStack) {
      this.stack.splice(start, howManyArgs);
    } else {
      this.stack.length = 0;
    }
    return false;
  }
}

/**
 * Decrypt a Sequence of Ciphertext Bytes to Produce the Original Sequence
 * of Plaintext Bytes. The function takes a key as a parameter which can be
 * for decrypting the eexec block or for decoding charStrings.
 */
const EEXEC_ENCRYPT_KEY = 55665;
const CHAR_STRS_ENCRYPT_KEY = 4330;

function isHexDigit(code) {
  return (
    (code >= 48 && code <= 57) || // '0'-'9'
    (code >= 65 && code <= 70) || // 'A'-'F'
    (code >= 97 && code <= 102) // 'a'-'f'
  );
}

function isSpecial(c) {
  return (
    c === /* '/' = */ 0x2f ||
    c === /* '[' = */ 0x5b ||
    c === /* ']' = */ 0x5d ||
    c === /* '{' = */ 0x7b ||
    c === /* '}' = */ 0x7d ||
    c === /* '(' = */ 0x28 ||
    c === /* ')' = */ 0x29
  );
}

/**
 * Type1Parser encapsulate the needed code for parsing a Type1 font program.
 * Some of its logic depends on the Type2 charstrings structure.
 * NOTE: This doesn't really parse the font since that would require evaluation
 *       of PostScript, but it is possible in most cases to extract what we need
 *       without a full parse.
 */
class Type1Parser {
  constructor(stream, encrypted, seacAnalysisEnabled) {
    if (encrypted) {
      const data = stream.getBytes();
      const isBinary = !(
        (isHexDigit(data[0]) || isWhiteSpace(data[0])) &&
        isHexDigit(data[1]) &&
        isHexDigit(data[2]) &&
        isHexDigit(data[3]) &&
        isHexDigit(data[4]) &&
        isHexDigit(data[5]) &&
        isHexDigit(data[6]) &&
        isHexDigit(data[7])
      );
      stream = new Stream(
        isBinary
          ? decrypt(data, EEXEC_ENCRYPT_KEY, 4)
          : decryptAscii(data, EEXEC_ENCRYPT_KEY, 4)
      );
    }
    this.seacAnalysisEnabled = !!seacAnalysisEnabled;

this.stream = stream;
    this.nextChar();
  }

readNumberArray() {
    this.getToken(); // read '[' or '{' (arrays can start with either)
    const array = [];
    while (true) {
      const token = this.getToken();
      if (token === null || token === "]" || token === "}") {
        break;
      }
      array.push(parseFloat(token || 0));
    }
    return array;
  }

readNumber() {
    const token = this.getToken();
    return parseFloat(token || 0);
  }

readInt() {
    // Use '| 0' to prevent setting a double into length such as the double
    // does not flow into the loop variable.
    const token = this.getToken();
    return parseInt(token || 0, 10) | 0;
  }

readBoolean() {
    const token = this.getToken();
    // Use 1 and 0 since that's what type2 charstrings use.
    return token === "true" ? 1 : 0;
  }

nextChar() {
    return (this.currentChar = this.stream.getByte());
  }

prevChar() {
    this.stream.skip(-2);
    return (this.currentChar = this.stream.getByte());
  }

getToken() {
    // Eat whitespace and comments.
    let comment = false;
    let ch = this.currentChar;
    while (true) {
      if (ch === -1) {
        return null;
      }

if (comment) {
        if (ch === 0x0a || ch === 0x0d) {
          comment = false;
        }
      } else if (ch === /* '%' = */ 0x25) {
        comment = true;
      } else if (!isWhiteSpace(ch)) {
        break;
      }
      ch = this.nextChar();
    }
    if (isSpecial(ch)) {
      this.nextChar();
      return String.fromCharCode(ch);
    }
    let token = "";
    do {
      token += String.fromCharCode(ch);
      ch = this.nextChar();
    } while (ch >= 0 && !isWhiteSpace(ch) && !isSpecial(ch));
    return token;
  }

readCharStrings(bytes, lenIV) {
    if (lenIV === -1) {
      // This isn't in the spec, but Adobe's tx program handles -1
      // as plain text.
      return bytes;
    }
    return decrypt(bytes, CHAR_STRS_ENCRYPT_KEY, lenIV);
  }

/*
   * Returns an object containing a Subrs array and a CharStrings
   * array extracted from and eexec encrypted block of data
   */
  extractFontProgram(properties) {
    const stream = this.stream;

if (token !== "/") {
              continue;
            }
            const glyph = this.getToken();
            length = this.readInt();
            this.getToken(); // read in 'RD' or '-|'
            data = length > 0 ? stream.getBytes(length) : new Uint8Array(0);
            lenIV = program.properties.privateData.lenIV;
            const encoded = this.readCharStrings(data, lenIV);
            this.nextChar();
            token = this.getToken(); // read in 'ND' or '|-'
            if (token === "noaccess") {
              this.getToken(); // read in 'def'
            } else if (token === "/") {
              // The expected 'ND' or '|-' token is missing, avoid swallowing
              // the start of the next glyph (fixes issue14462_reduced.pdf).
              this.prevChar();
            }
            charstrings.push({
              glyph,
              encoded,
            });
          }
          break;
        case "Subrs":
          this.readInt(); // num
          this.getToken(); // read in 'array'
          while (this.getToken() === "dup") {
            const index = this.readInt();
            length = this.readInt();
            this.getToken(); // read in 'RD' or '-|'
            data = length > 0 ? stream.getBytes(length) : new Uint8Array(0);
            lenIV = program.properties.privateData.lenIV;
            const encoded = this.readCharStrings(data, lenIV);
            this.nextChar();
            token = this.getToken(); // read in 'NP' or '|'
            if (token === "noaccess") {
              this.getToken(); // read in 'put'
            }
            subrs[index] = encoded;
          }
          break;
        case "BlueValues":
        case "OtherBlues":
        case "FamilyBlues":
        case "FamilyOtherBlues":
          const blueArray = this.readNumberArray();
          // *Blue* values may contain invalid data: disables reading of
          // those values when hinting is disabled.
          if (
            blueArray.length > 0 &&
            blueArray.length % 2 === 0 &&
            HINTING_ENABLED
          ) {
            program.properties.privateData[token] = blueArray;
          }
          break;
        case "StemSnapH":
        case "StemSnapV":
          program.properties.privateData[token] = this.readNumberArray();
          break;
        case "StdHW":
        case "StdVW":
          program.properties.privateData[token] = this.readNumberArray()[0];
          break;
        case "BlueShift":
        case "lenIV":
        case "BlueFuzz":
        case "BlueScale":
        case "LanguageGroup":
          program.properties.privateData[token] = this.readNumber();
          break;
        case "ExpansionFactor":
          // Firefox doesn't render correctly a font with a null factor on
          // Windows (see issue 15289), hence we just reset it to its default
          // value (0.06).
          program.properties.privateData[token] = this.readNumber() || 0.06;
          break;
        case "ForceBold":
          program.properties.privateData[token] = this.readBoolean();
          break;
      }
    }

for (const { encoded, glyph } of charstrings) {
      const charString = new Type1CharString();
      const error = charString.convert(
        encoded,
        subrs,
        this.seacAnalysisEnabled
      );
      let output = charString.output;
      if (error) {
        // It seems when FreeType encounters an error while evaluating a glyph
        // that it completely ignores the glyph so we'll mimic that behaviour
        // here and put an endchar to make the validator happy.
        output = [14];
      }
      const charStringObject = {
        glyphName: glyph,
        charstring: output,
        width: charString.width,
        lsb: charString.lsb,
        seac: charString.seac,
      };
      if (glyph === ".notdef") {
        // Make sure .notdef is at index zero (issue #11477).
        program.charstrings.unshift(charStringObject);
      } else {
        program.charstrings.push(charStringObject);
      }

// Attempt to replace missing widths, from the font dictionary /Widths
      // entry, with ones from the font data (fixes issue11150_reduced.pdf).
      if (properties.builtInEncoding) {
        const index = properties.builtInEncoding.indexOf(glyph);
        if (
          index > -1 &&
          properties.widths[index] === undefined &&
          index >= properties.firstChar &&
          index <= properties.lastChar
        ) {
          properties.widths[index] = charString.width;
        }
      }
    }

return program;
  }

extractFontHeader(properties) {
    let token;
    while ((token = this.getToken()) !== null) {
      if (token !== "/") {
        continue;
      }
      token = this.getToken();
      switch (token) {
        case "FontMatrix":
          const matrix = this.readNumberArray();
          properties.fontMatrix = matrix;
          break;
        case "Encoding":
          const encodingArg = this.getToken();
          let encoding;
          if (!/^\d+$/.test(encodingArg)) {
            // encoding name is specified
            encoding = getEncoding(encodingArg);
          } else {
            encoding = [];
            const size = parseInt(encodingArg, 10) | 0;
            this.getToken(); // read in 'array'

for (let j = 0; j < size; j++) {
              token = this.getToken();
              // skipping till first dup or def (e.g. ignoring for statement)
              while (token !== "dup" && token !== "def") {
                token = this.getToken();
                if (token === null) {
                  return; // invalid header
                }
              }
              if (token === "def") {
                break; // read all array data
              }
              const index = this.readInt();
              this.getToken(); // read in '/'
              const glyph = this.getToken();
              encoding[index] = glyph;
              this.getToken(); // read the in 'put'
            }
          }
          properties.builtInEncoding = encoding;
          break;
        case "FontBBox":
          const fontBBox = this.readNumberArray();
          // adjusting ascent/descent
          properties.ascent = Math.max(fontBBox[3], fontBBox[1]);
          properties.descent = Math.min(fontBBox[1], fontBBox[3]);
          properties.ascentScaled = true;
          break;
      }
    }
  }
}

export { Type1Parser };