fbreader/src/formats/chm/BitStream.h

   1 /*
   2  * Copyright (C) 2004-2008 Geometer Plus <contact@geometerplus.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  */
  19
  20 #ifndef __BITSTREAM_H__
  21 #define __BITSTREAM_H__
  22
  23 #include <string>
  24
  25 class BitStream {
  26
  27 public:
  28         static const int BufferSize;
  29
  30 public:
  31         BitStream();
  32         void setData(const std::string &data);
  33         void reset();
  34         unsigned int peek(unsigned char length);
  35         void remove(unsigned char length);
  36         unsigned int get(unsigned char length);
  37         unsigned int bytesLeft() const;
  38
  39         unsigned int get4BytesDirect();
  40         bool getBytesDirect(unsigned char *buffer, unsigned int length);
  41
  42 private:
  43         bool ensure(unsigned char length);
  44
  45 private:
  46         unsigned int myBuffer;
  47         unsigned char myBitCounter;
  48         const unsigned char *myByteStream;
  49         const unsigned char *myByteStreamEnd;
  50
  51 private:
  52         BitStream(const BitStream&);
  53         const BitStream &operator = (const BitStream&);
  54 };
  55
  56 inline BitStream::BitStream() : myBuffer(0), myBitCounter(0) {
  57 }
  58
  59 inline void BitStream::setData(const std::string &data) {
  60         myByteStream = (const unsigned char*)data.data();
  61         myByteStreamEnd = myByteStream + data.length();
  62         myBuffer = 0;
  63         myBitCounter = 0;
  64 }
  65
  66 inline void BitStream::reset() {
  67         myByteStream -= myBitCounter / 8;
  68         myBuffer = 0;
  69         myBitCounter = 0;
  70 }
  71
  72 inline bool BitStream::ensure(unsigned char length) {
  73         while ((myBitCounter < length) && (bytesLeft() >= 2)) {
  74                 myBuffer |= ((myByteStream[1] << 8) | myByteStream[0]) << (BitStream::BufferSize - 16 - myBitCounter);
  75                 myBitCounter += 16;
  76                 myByteStream += 2;
  77         }
  78         return myBitCounter >= length;
  79 }
  80
  81 inline unsigned int BitStream::peek(unsigned char length) {
  82         ensure(length);
  83         return (length > 0) ? (myBuffer >> (BufferSize - length)) : 0;
  84 }
  85
  86 inline void BitStream::remove(unsigned char length) {
  87         if (ensure(length)) {
  88                 myBuffer <<= length;
  89                 myBitCounter -= length;
  90         }
  91 }
  92
  93 inline unsigned int BitStream::get(unsigned char length) {
  94         unsigned int bits;
  95         if (length > 16) {
  96                 bits = peek(length - 16) << 16;
  97                 remove(length - 16);
  98                 bits += peek(16);
  99                 remove(16);
 100         } else {
 101                 bits = peek(length);
 102                 remove(length);
 103         }
 104         return bits;
 105 }
 106
 107 inline unsigned int BitStream::bytesLeft() const {
 108         return myByteStreamEnd - myByteStream;
 109 }
 110
 111 #endif /* __BITSTREAM_H__ */