BitPacker.cpp

#include "BitPacker.h" 
BitPacker::BitPacker(){
    bitBuffer = 0;
    bitCount = 0;
}
BitPacker::~BitPacker(){
    if (outputFile.is_open())
        outputFile.close();
}

void BitPacker::initWriter( const std::string& outputFName, const std::string& inputFName){
    outputFile.open(outputFName, std::ios::binary);
    if (!outputFile)
        throw std::runtime_error("Failed to open output file " + outputFName); 
    
    for (int i = 0; i < inputFName.size(); ++i) {
        char c = inputFName[i];
        outputFile.write(&c, sizeof(char));
    }
    char separator = 'N';
    // separator - the end of the string
    outputFile.write(&separator, sizeof(char));

}

void BitPacker::resetBuffer() {

    bitBuffer = 0;
    bitCount = 0;
}

void BitPacker::packBits(uint16_t bits, int lenght) {
    if( bitCount > 0){ // if there are bits in buffer left from last time 
        bitBuffer = bitBuffer | (bits << bitCount); // 10101010 << 4 = 10101010000 
                                                    
        
        writeByte(bitBuffer); //write a formed byte 
            
        bits = bits >> (8  - bitCount); // shifting for 'clearing' bits that were written
        
        lenght -= 8 - bitCount; //to keep track of the remaining bits left to write.

        resetBuffer();
    }
    while(lenght > 0){
        if(lenght >= 8){ // 1 byte or more left
            writeByte(bits);
            bits >>= 8; // remove the bits that are already in file
            lenght -= 8; 
        }
        else{ // if less than a byte is left
        //add whats left to buffer
            bitCount = lenght; 
            bitBuffer = bits;
            lenght = 0; // reset to end the while loop
        }
    }
}

void BitPacker::writeByte(uint16_t byte) {

    outputFile.put(static_cast<char>(byte));
}

void BitPacker::writeLast() {
    uint16_t bits = 0; 
    if(bitCount > 0) { // if there are bits in the buffer left from last time
        writeByte(bitBuffer); // write the buffer to the file
    }
}
void BitPacker::closeStream(){
    outputFile.put(EOF); 
    outputFile.close();
}