model.cpp

/**
 * @file model.cpp
 * @author Marián Tarageľ (xtarag01)
 * @brief Model and RLE encoding
 * @date 8.5.2024
 */

#include <vector>
#include <cstdint>

std::vector<uint8_t> diff_model(std::vector<uint8_t> buffer)
{
    uint8_t prev = buffer[0];
    for (unsigned long int i = 1; i < buffer.size(); i++) {
        uint8_t copy = buffer[i];
        buffer[i] -= prev;
        prev = copy;
    }
    
    return buffer;
}

std::vector<uint8_t> rle(std::vector<uint8_t> buffer)
{
    std::vector<uint8_t> rle_buffer;
    unsigned long int i = 0;
    while (i < buffer.size()) {
        uint8_t value = buffer[i];
        uint8_t count = 1;

        if (i + count < buffer.size()) { // check whether we are still in buffer
            // while the symbol is the same increase value count
            while (buffer[i + count] == value) {
                count++;
                if ((count == 255) || (i + count == buffer.size())) // maximum possible value count is 255 (8 bits)
                    break;
            }
        }

        // encode in tuples (count, value)
        rle_buffer.push_back(count);
        rle_buffer.push_back(value);
        i += count;
    }

    return rle_buffer;
}

std::vector<uint8_t> inverse_diff_model(std::vector<uint8_t> buffer)
{
    std::vector<uint8_t> output;
    uint8_t prev = buffer[0];
    output.push_back(prev);

    for (unsigned long int i = 1; i < buffer.size(); i++) {
        uint8_t value = buffer[i] + prev;
        output.push_back(value);
        prev = value;
    }

    return output;
}

std::vector<uint8_t> inverse_rle(std::vector<uint8_t> buffer)
{
    std::vector<uint8_t> output;

    for (unsigned long int i = 0; i < buffer.size(); i += 2) {
        uint8_t count = buffer[i];
        uint8_t value = buffer[i + 1];

        for (unsigned long int i = 0; i < count; i++)
            output.push_back(value);
    }

    return output;    
}