pdfjs-dist/lib/core/arithmetic_decoder.js

/**
 * @licstart The following is the entire license notice for the
 * Javascript code in this page
 *
 * 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.
 *
 * @licend The above is the entire license notice for the
 * Javascript code in this page
 */
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.ArithmeticDecoder = void 0;

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

function _defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

function _createClass(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties(Constructor.prototype, protoProps); if (staticProps) _defineProperties(Constructor, staticProps); return Constructor; }

var QeTable = [{
  qe: 0x5601,
  nmps: 1,
  nlps: 1,
  switchFlag: 1
}, {
  qe: 0x3401,
  nmps: 2,
  nlps: 6,
  switchFlag: 0
}, {
  qe: 0x1801,
  nmps: 3,
  nlps: 9,
  switchFlag: 0
}, {
  qe: 0x0AC1,
  nmps: 4,
  nlps: 12,
  switchFlag: 0
}, {
  qe: 0x0521,
  nmps: 5,
  nlps: 29,
  switchFlag: 0
}, {
  qe: 0x0221,
  nmps: 38,
  nlps: 33,
  switchFlag: 0
}, {
  qe: 0x5601,
  nmps: 7,
  nlps: 6,
  switchFlag: 1
}, {
  qe: 0x5401,
  nmps: 8,
  nlps: 14,
  switchFlag: 0
}, {
  qe: 0x4801,
  nmps: 9,
  nlps: 14,
  switchFlag: 0
}, {
  qe: 0x3801,
  nmps: 10,
  nlps: 14,
  switchFlag: 0
}, {
  qe: 0x3001,
  nmps: 11,
  nlps: 17,
  switchFlag: 0
}, {
  qe: 0x2401,
  nmps: 12,
  nlps: 18,
  switchFlag: 0
}, {
  qe: 0x1C01,
  nmps: 13,
  nlps: 20,
  switchFlag: 0
}, {
  qe: 0x1601,
  nmps: 29,
  nlps: 21,
  switchFlag: 0
}, {
  qe: 0x5601,
  nmps: 15,
  nlps: 14,
  switchFlag: 1
}, {
  qe: 0x5401,
  nmps: 16,
  nlps: 14,
  switchFlag: 0
}, {
  qe: 0x5101,
  nmps: 17,
  nlps: 15,
  switchFlag: 0
}, {
  qe: 0x4801,
  nmps: 18,
  nlps: 16,
  switchFlag: 0
}, {
  qe: 0x3801,
  nmps: 19,
  nlps: 17,
  switchFlag: 0
}, {
  qe: 0x3401,
  nmps: 20,
  nlps: 18,
  switchFlag: 0
}, {
  qe: 0x3001,
  nmps: 21,
  nlps: 19,
  switchFlag: 0
}, {
  qe: 0x2801,
  nmps: 22,
  nlps: 19,
  switchFlag: 0
}, {
  qe: 0x2401,
  nmps: 23,
  nlps: 20,
  switchFlag: 0
}, {
  qe: 0x2201,
  nmps: 24,
  nlps: 21,
  switchFlag: 0
}, {
  qe: 0x1C01,
  nmps: 25,
  nlps: 22,
  switchFlag: 0
}, {
  qe: 0x1801,
  nmps: 26,
  nlps: 23,
  switchFlag: 0
}, {
  qe: 0x1601,
  nmps: 27,
  nlps: 24,
  switchFlag: 0
}, {
  qe: 0x1401,
  nmps: 28,
  nlps: 25,
  switchFlag: 0
}, {
  qe: 0x1201,
  nmps: 29,
  nlps: 26,
  switchFlag: 0
}, {
  qe: 0x1101,
  nmps: 30,
  nlps: 27,
  switchFlag: 0
}, {
  qe: 0x0AC1,
  nmps: 31,
  nlps: 28,
  switchFlag: 0
}, {
  qe: 0x09C1,
  nmps: 32,
  nlps: 29,
  switchFlag: 0
}, {
  qe: 0x08A1,
  nmps: 33,
  nlps: 30,
  switchFlag: 0
}, {
  qe: 0x0521,
  nmps: 34,
  nlps: 31,
  switchFlag: 0
}, {
  qe: 0x0441,
  nmps: 35,
  nlps: 32,
  switchFlag: 0
}, {
  qe: 0x02A1,
  nmps: 36,
  nlps: 33,
  switchFlag: 0
}, {
  qe: 0x0221,
  nmps: 37,
  nlps: 34,
  switchFlag: 0
}, {
  qe: 0x0141,
  nmps: 38,
  nlps: 35,
  switchFlag: 0
}, {
  qe: 0x0111,
  nmps: 39,
  nlps: 36,
  switchFlag: 0
}, {
  qe: 0x0085,
  nmps: 40,
  nlps: 37,
  switchFlag: 0
}, {
  qe: 0x0049,
  nmps: 41,
  nlps: 38,
  switchFlag: 0
}, {
  qe: 0x0025,
  nmps: 42,
  nlps: 39,
  switchFlag: 0
}, {
  qe: 0x0015,
  nmps: 43,
  nlps: 40,
  switchFlag: 0
}, {
  qe: 0x0009,
  nmps: 44,
  nlps: 41,
  switchFlag: 0
}, {
  qe: 0x0005,
  nmps: 45,
  nlps: 42,
  switchFlag: 0
}, {
  qe: 0x0001,
  nmps: 45,
  nlps: 43,
  switchFlag: 0
}, {
  qe: 0x5601,
  nmps: 46,
  nlps: 46,
  switchFlag: 0
}];

var ArithmeticDecoder =
/*#__PURE__*/
function () {
  function ArithmeticDecoder(data, start, end) {
    _classCallCheck(this, ArithmeticDecoder);

    this.data = data;
    this.bp = start;
    this.dataEnd = end;
    this.chigh = data[start];
    this.clow = 0;
    this.byteIn();
    this.chigh = this.chigh << 7 & 0xFFFF | this.clow >> 9 & 0x7F;
    this.clow = this.clow << 7 & 0xFFFF;
    this.ct -= 7;
    this.a = 0x8000;
  }

  _createClass(ArithmeticDecoder, [{
    key: "byteIn",
    value: function byteIn() {
      var data = this.data;
      var bp = this.bp;

      if (data[bp] === 0xFF) {
        if (data[bp + 1] > 0x8F) {
          this.clow += 0xFF00;
          this.ct = 8;
        } else {
          bp++;
          this.clow += data[bp] << 9;
          this.ct = 7;
          this.bp = bp;
        }
      } else {
        bp++;
        this.clow += bp < this.dataEnd ? data[bp] << 8 : 0xFF00;
        this.ct = 8;
        this.bp = bp;
      }

      if (this.clow > 0xFFFF) {
        this.chigh += this.clow >> 16;
        this.clow &= 0xFFFF;
      }
    }
  }, {
    key: "readBit",
    value: function readBit(contexts, pos) {
      var cx_index = contexts[pos] >> 1,
          cx_mps = contexts[pos] & 1;
      var qeTableIcx = QeTable[cx_index];
      var qeIcx = qeTableIcx.qe;
      var d;
      var a = this.a - qeIcx;

      if (this.chigh < qeIcx) {
        if (a < qeIcx) {
          a = qeIcx;
          d = cx_mps;
          cx_index = qeTableIcx.nmps;
        } else {
          a = qeIcx;
          d = 1 ^ cx_mps;

          if (qeTableIcx.switchFlag === 1) {
            cx_mps = d;
          }

          cx_index = qeTableIcx.nlps;
        }
      } else {
        this.chigh -= qeIcx;

        if ((a & 0x8000) !== 0) {
          this.a = a;
          return cx_mps;
        }

        if (a < qeIcx) {
          d = 1 ^ cx_mps;

          if (qeTableIcx.switchFlag === 1) {
            cx_mps = d;
          }

          cx_index = qeTableIcx.nlps;
        } else {
          d = cx_mps;
          cx_index = qeTableIcx.nmps;
        }
      }

      do {
        if (this.ct === 0) {
          this.byteIn();
        }

        a <<= 1;
        this.chigh = this.chigh << 1 & 0xFFFF | this.clow >> 15 & 1;
        this.clow = this.clow << 1 & 0xFFFF;
        this.ct--;
      } while ((a & 0x8000) === 0);

      this.a = a;
      contexts[pos] = cx_index << 1 | cx_mps;
      return d;
    }
  }]);

  return ArithmeticDecoder;
}();

exports.ArithmeticDecoder = ArithmeticDecoder;