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      1 // Copyright 2014 PDFium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
      6 
      7 #include "JBig2_ArithIntDecoder.h"
      8 CJBig2_ArithIntDecoder::CJBig2_ArithIntDecoder()
      9 {
     10     IAx = (JBig2ArithCtx*)m_pModule->JBig2_Malloc2(sizeof(JBig2ArithCtx), 512);
     11     JBIG2_memset(IAx, 0, sizeof(JBig2ArithCtx) * 512);
     12 }
     13 CJBig2_ArithIntDecoder::~CJBig2_ArithIntDecoder()
     14 {
     15     m_pModule->JBig2_Free(IAx);
     16 }
     17 int CJBig2_ArithIntDecoder::decode(CJBig2_ArithDecoder *pArithDecoder, int *nResult)
     18 {
     19     int PREV, V;
     20     int S, D;
     21     int nNeedBits, nTemp, i;
     22     PREV = 1;
     23     S = pArithDecoder->DECODE(IAx + PREV);
     24     PREV = (PREV << 1) | S;
     25     D = pArithDecoder->DECODE(IAx + PREV);
     26     PREV = (PREV << 1) | D;
     27     if(D) {
     28         D = pArithDecoder->DECODE(IAx + PREV);
     29         PREV = (PREV << 1) | D;
     30         if(D) {
     31             D = pArithDecoder->DECODE(IAx + PREV);
     32             PREV = (PREV << 1) | D;
     33             if(D) {
     34                 D = pArithDecoder->DECODE(IAx + PREV);
     35                 PREV = (PREV << 1) | D;
     36                 if(D) {
     37                     D = pArithDecoder->DECODE(IAx + PREV);
     38                     PREV = (PREV << 1) | D;
     39                     if(D) {
     40                         nNeedBits = 32;
     41                         V = 4436;
     42                     } else {
     43                         nNeedBits = 12;
     44                         V = 340;
     45                     }
     46                 } else {
     47                     nNeedBits = 8;
     48                     V = 84;
     49                 }
     50             } else {
     51                 nNeedBits = 6;
     52                 V = 20;
     53             }
     54         } else {
     55             nNeedBits = 4;
     56             V = 4;
     57         }
     58     } else {
     59         nNeedBits = 2;
     60         V = 0;
     61     }
     62     nTemp = 0;
     63     for(i = 0; i < nNeedBits; i++) {
     64         D = pArithDecoder->DECODE(IAx + PREV);
     65         if(PREV < 256) {
     66             PREV = (PREV << 1) | D;
     67         } else {
     68             PREV = (((PREV << 1) | D) & 511) | 256;
     69         }
     70         nTemp = (nTemp << 1) | D;
     71     }
     72     V += nTemp;
     73     if(S == 1 && V > 0) {
     74         V = -V;
     75     }
     76     *nResult = V;
     77     if(S == 1 && V == 0) {
     78         return JBIG2_OOB;
     79     }
     80     return 0;
     81 }
     82 CJBig2_ArithIaidDecoder::CJBig2_ArithIaidDecoder(unsigned char SBSYMCODELENA)
     83 {
     84     SBSYMCODELEN = SBSYMCODELENA;
     85     IAID = (JBig2ArithCtx*)m_pModule->JBig2_Malloc2(sizeof(JBig2ArithCtx), (1 << SBSYMCODELEN));
     86     JBIG2_memset(IAID, 0, sizeof(JBig2ArithCtx) * (int)(1 << SBSYMCODELEN));
     87 }
     88 CJBig2_ArithIaidDecoder::~CJBig2_ArithIaidDecoder()
     89 {
     90     m_pModule->JBig2_Free(IAID);
     91 }
     92 int CJBig2_ArithIaidDecoder::decode(CJBig2_ArithDecoder *pArithDecoder, int *nResult)
     93 {
     94     int PREV;
     95     int D;
     96     int i;
     97     PREV = 1;
     98     for(i = 0; i < SBSYMCODELEN; i++) {
     99         D = pArithDecoder->DECODE(IAID + PREV);
    100         PREV = (PREV << 1) | D;
    101     }
    102     PREV = PREV - (1 << SBSYMCODELEN);
    103     *nResult = PREV;
    104     return 0;
    105 }
    106