core/src/fxcodec/jbig2/JBig2_HuffmanDecoder.cpp

// Copyright 2014 PDFium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com

#include "JBig2_HuffmanDecoder.h"
CJBig2_HuffmanDecoder::CJBig2_HuffmanDecoder(CJBig2_BitStream *pStream)
{
    m_pStream = pStream;
}
CJBig2_HuffmanDecoder::~CJBig2_HuffmanDecoder()
{
}
int CJBig2_HuffmanDecoder::decodeAValue(CJBig2_HuffmanTable *pTable, int *nResult)
{
    int nVal, nTmp, i, nBits;
    nVal = 0;
    nBits = 0;
    while(1) {
        if(m_pStream->read1Bit(&nTmp) == -1) {
            return -1;
        }
        nVal = (nVal << 1) | nTmp;
        nBits ++;
        for(i = 0; i < pTable->NTEMP; i++) {
            if((pTable->PREFLEN[i] == nBits) && (pTable->CODES[i] == nVal)) {
                if((pTable->HTOOB == 1) && (i == pTable->NTEMP - 1)) {
                    return JBIG2_OOB;
                }
                if(m_pStream->readNBits(pTable->RANGELEN[i], &nTmp) == -1) {
                    return -1;
                }
                if(pTable->HTOOB) {
                    if(i == pTable->NTEMP - 3) {
                        *nResult = pTable->RANGELOW[i] - nTmp;
                        return 0;
                    } else {
                        *nResult = pTable->RANGELOW[i] + nTmp;
                        return 0;
                    }
                } else {
                    if(i == pTable->NTEMP - 2) {
                        *nResult = pTable->RANGELOW[i] - nTmp;
                        return 0;
                    } else {
                        *nResult = pTable->RANGELOW[i] + nTmp;
                        return 0;
                    }
                }
            }
        }
    }
    return -2;
}