ASCII85

main.cpp

#include <cmath>
#include <fstream>
#include <iostream>
#include <sys/stat.h>
#include <vector>

int32_t ascii_to_int(std::string c) {
    int32_t rv;
    for (size_t i=0; i<c.size(); ++i) {
        rv <<= 8;
        rv |= (int)c[i] & 0xFF;
    }
    return rv;
}

int32_t base85_to_int(std::string c) {
    int32_t rv = 0;
    for (int i=c.size()-1; i>=0; --i) {
        int x = ((int) c[i]) - 33;
        rv += x * (pow(85, (c.size()-i-1)));
    }
    return rv;
}

std::string int_to_base85(int32_t x) {
    std::string rv;
    int32_t rem = 0;
    for (int i=4; i>=0; --i) {
        rem = x % 85;
        rv.insert(rv.begin(), (char) (rem + 33));
        x = (x-rem) / 85;
    }
    return rv;
}

std::string int_to_ascii(int32_t x) {
    std::string rv;
    int32_t rem = 0;
    for (int i=4; i>0; --i) {
        rem = x & 127;
        rv.insert(rv.begin(), (char) rem);
        x >>= 8;
    }
    return rv;
}

int code(std::ifstream & in, int in_len, char pad_char, int32_t (*f1)(std::string), std::string (*f2)(int32_t))
{
    std::string cx("     ");
    int i = 0;
    int j = 0;
    int rv = 0;
    std::string whole;
    while (!in.eof()) {
        j = 0;
        for (i=0; i<in_len && !in.eof(); ++i) in.get(cx[i]);
        if (in.eof() && i < in_len) {
            for (j=i; j<in_len+1; ++j) cx[j-1] = pad_char;
            j -= i;
        }
        i = 0;
        whole.append(f2(f1(cx)));
    }
    if (j>0) whole.erase(whole.size()-j);
    std::cout << whole << std::endl;
    return rv;
}

int main(int argc, char *argv[])
{
    if (argc < 3) {
        std::cout << "Usage: " << argv[0] << "OPTION FILENAME" << std::endl;
        std::cout << "\t-e\tencode to ASCII85" << std::endl;
        std::cout << "\t-d\tdecode from ASCII85" << std::endl;
        return 0;
    }
    std::string opt = argv[1];
    if (opt != "-e" && opt != "-d") {
        std::cout << "Wrong option: " << opt << std::endl;
        return 0;
    }
    bool encodingMode = (opt == "-e");
    char * filename;
    filename = argv[2];

    struct stat buf;
    stat(filename, &buf);
    std::cerr << "Reading " << filename << ", size: " << buf.st_size << std::endl;

    std::ifstream in;
    in.open(filename, std::ios::in | std::ios::binary);
    if (!in || !in.is_open()) {
        std::cerr << "Can't open input file " << filename << std::endl;
        return 1;
    }

    int rv = 1;
    if (encodingMode) {
        rv = code(in, 4, '\0', ascii_to_int, int_to_base85);
    } else {
        rv = code(in, 5, 'u', base85_to_int, int_to_ascii);
    }
    if (in.is_open()) in.close();
    return rv;
}