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BitsReader.h

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00001 // BitsReader.h:  bits reader, for Gnash.
00002 // 
00003 //   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Free Software
00004 //   Foundation, Inc
00005 // 
00006 // This program is free software; you can redistribute it and/or modify
00007 // it under the terms of the GNU General Public License as published by
00008 // the Free Software Foundation; either version 3 of the License, or
00009 // (at your option) any later version.
00010 // 
00011 // This program is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 // 
00016 // You should have received a copy of the GNU General Public License
00017 // along with this program; if not, write to the Free Software
00018 // Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
00019 //
00020 
00021 
00022 #ifndef BITSREADER_H
00023 #define BITSREADER_H
00024 
00025 #include "dsodefs.h"
00026 #include "log.h"
00027 
00028 #include <sstream>
00029 #include <cassert>
00030 #include <boost/cstdint.hpp> // for boost::uint32_t used in this file
00031 
00032 namespace gnash {
00033 
00035 //
00039 class DSOEXPORT BitsReader 
00040 {
00041 public:
00042         typedef unsigned char byte;
00043 
00045         BitsReader(const byte* input, size_t len)
00046                 :
00047                 start(input),
00048                 ptr(start),
00049                 end(start+len),
00050                 usedBits(0)
00051         {
00052         }
00053 
00055         //
00062         BitsReader(const BitsReader& from, size_t len)
00063                 :
00064                 start(from.ptr),
00065                 ptr(start),
00066                 end(start+len),
00067                 usedBits(from.usedBits) 
00068         {
00069         }
00070 
00071         ~BitsReader() {}
00072 
00073         size_t size() const
00074         {
00075                 return end-start;
00076         }
00077 
00079         void setBuffer(byte* input, size_t len)
00080         {
00081                 start = ptr = input;
00082                 end = start+len;
00083                 usedBits = 0;
00084         }
00085 
00090         unsigned read_uint(unsigned short bitcount);
00091 
00095         bool read_bit();
00096 
00101         boost::int32_t read_sint(unsigned short bitcount);
00102 
00104         boost::uint8_t  read_u8()
00105         {
00106                 align();
00107                 return *ptr++;
00108         }
00109 
00111     boost::int8_t read_s8()
00112         {
00113                 return static_cast<boost::int8_t>(read_u8());
00114         }
00115 
00117         boost::uint16_t read_u16()
00118         {
00119                 align();
00120                 assert(ptr+2 < end);
00121                 boost::uint16_t result = *ptr++;
00122                 result |= *ptr++ << 8;
00123                 return result ;
00124         }
00125 
00127         boost::int16_t  read_s16()
00128         {
00129                 return static_cast<boost::int16_t>(read_u16());
00130         }
00131 
00133         boost::uint32_t read_u32()
00134         {
00135                 align();
00136                 assert(ptr+4 < end);
00137                 boost::uint32_t result = *ptr++;
00138                 result |= *ptr++ << 8;
00139                 result |= *ptr++ << 16;
00140                 result |= *ptr++ << 24;
00141                 return(result);
00142         }
00143 
00145         boost::int32_t read_s32()
00146         {
00147                 return static_cast<boost::int32_t>(read_u32());
00148         }
00149 
00153         void align()
00154         {
00155                 if ( usedBits ) advanceToNextByte();
00156         }
00157 
00159         bool gotBits(boost::uint32_t nbits)
00160         {
00161                 boost::uint32_t gotbits = 8-usedBits +8*(end-ptr-1);
00162                 if (gotbits > nbits) return true;
00163                 else return false;
00164         }
00165 
00166 private:
00167 
00168         void advanceToNextByte()
00169         {
00170                 if ( ++ptr == end )
00171                 {
00172                         log_debug("Going round");
00173                         ptr=start;
00174                 }
00175                 usedBits=0;
00176         }
00177 
00179         const byte* start;
00180 
00182         const byte* ptr;
00183 
00185         const byte* end;
00186 
00188         unsigned usedBits;
00189 
00190 };
00191 
00192 
00193 }       // end namespace gnash
00194 
00195 
00196 #endif // BITSREADER_H
00197 
00198 
00199 // Local Variables:
00200 // mode: C++
00201 // c-basic-offset: 8 
00202 // tab-width: 8
00203 // indent-tabs-mode: t
00204 // End:

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