112 lines
3.2 KiB
C++
112 lines
3.2 KiB
C++
#define DEBUG 0
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#include "eyd_bitreader.hh"
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namespace EydLib {
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/*
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* int _group_pos;
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int _fd;
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*/
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BitReader::BitReader(int size, int buffer_size = 1024){
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// tous les groupes de bits seront de la taille donnée
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this->_bitgroup_size = size;
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this->_wanted_buffer_size = buffer_size;
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this->_real_buffer_size = 0;
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this->_read_buffer = new char[this->_wanted_buffer_size];
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this->_file_desc = -1;
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this->_current_bit_position = (8 * buffer_size) + 1; // on dépasse volontairement
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}
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BitReader::~BitReader(){
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delete(this->_read_buffer);
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}
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void BitReader::open(std::string filename){
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this->_file_desc = ::open(filename.c_str(), O_RDONLY);
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this->_eof = false;
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}
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/*
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BitGroup * BitReader::read(int size){
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int i;
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BitGroup * result = new BitGroup[size];
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for (i=0; i<size; i++){
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result[i] = this->read_once();
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}
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return result;
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}
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*/
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bool BitReader::getBitAt(int position){
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// on attrappe la bonne case du tableau
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// on shift dans le bon sens
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// on retourne la valeur du bit.
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int size_of_char = 8 * sizeof(char);
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int i;
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int index_of_char = position / size_of_char;
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int shift_of_char = position % size_of_char;
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char reader;
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if (position > this->_real_buffer_size * size_of_char){
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//FIXME: throw exception
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} else {
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reader = this->_read_buffer[index_of_char];
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if (shift_of_char > 0){ reader = reader << shift_of_char; reader = reader >> shift_of_char; }
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reader = reader >> (size_of_char - shift_of_char - 1 );
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pDEBUG("BitReader::getBitAt","->%c<- shift %d = %d\n",this->_read_buffer[index_of_char], shift_of_char, reader);
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}
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return reader;
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}
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ssize_t BitReader::readDirect(void *buf, size_t count){
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return ::read(this->_file_desc, buf, count);
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}
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BitGroup BitReader::read(){
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int i;
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bool bitValue;
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int size_of_char = 8 * sizeof(char);
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BitGroup result(this->_bitgroup_size);
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if (this->_eof) { throw eBitReaderEndOfFile(); }
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if (this->_file_desc < 0){ throw eBitReaderBadFileDescriptor(); }
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for (i=0; i < this->_bitgroup_size; i++){
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if (this->_current_bit_position >= (this->_wanted_buffer_size * 8)){
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// on charge un nouveau bout de fichier
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this->_real_buffer_size = ::read(this->_file_desc, this->_read_buffer, this->_wanted_buffer_size);
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pDEBUG("BitReader::read","read() -> buffer()\n");
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pDEBUG("BitReader::read","READ BUFFER(%d): %s\n",this->_real_buffer_size, this->_read_buffer);
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this->_current_bit_position = 0;
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}
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if (this->_current_bit_position < this->_real_buffer_size * 8){
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//printf("TMP result = %s",result.toString().c_str());
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bitValue = this->getBitAt(this->_current_bit_position);
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result.setBitAt(i, bitValue);
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} else {
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// dans le cas ou on dépasse la fin du fichier avec un mauvais alignement
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this->_eof = true;
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if (i==0){ // on est sur le premier caractère
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throw eBitReaderEndOfFile();
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} else {
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BitGroup eof_bg(i);
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pDEBUG("BitReader::read","SMALLER BITGROUP ! (%d)\n",i);
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for (int j=0; j<i; j++){
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eof_bg.setBitAt(j, result.getBitAt(j));
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}
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result = eof_bg;
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break;
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}
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}
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this->_current_bit_position += 1;
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}
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return result;
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}
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void BitReader::close(){
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::close(this->_file_desc);
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}
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}
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