pdfjs-dist/lib/core/arithmetic_decoder.js

/* Copyright 2017 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.
 */
'use strict';
var ArithmeticDecoder = function ArithmeticDecoderClosure() {
 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
  }
 ];
 function ArithmeticDecoder(data, start, end) {
  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;
 }
 ArithmeticDecoder.prototype = {
  byteIn: function ArithmeticDecoder_byteIn() {
   var data = this.data;
   var bp = this.bp;
   if (data[bp] === 0xFF) {
    var b1 = data[bp + 1];
    if (b1 > 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;
   }
  },
  readBit: function ArithmeticDecoder_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;