Tarstats-pp/main.cpp

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <cmath>
#include <map>

// checks if a 512byte block consist only of 0 or \0
bool eof (const char* buf) {
    std::string test(&buf[0]);
    std::erase(test, '\0');
    std::erase(test, '0');
    if (test.size() == 0)
        return 1;
    return 0;
}

// gets name of an item (for test purposes)
std::string getitemname (const char* buf) {
    std::string name (&buf[0], 100);
    std::erase(name, '\0');
    return name;
}

// gets size of an item in bytes. assumes octal encoding.
uint64_t getitemsize(const char* buf){
    std::string asciisize(&buf[124], 11); // at offset 124 because first byte marks octal or base256 coding
    uint64_t itemsize{};
    uint8_t power = 10;
    for (auto i : asciisize) {
        uint8_t value = i - '0';
        itemsize += static_cast<uint64_t >(value * std::pow(8, power));
        power--;
    }
    return itemsize;
}

// gets type of an item
std::string getitemtype(char &n) {
    // read itemtype
    switch (n){
        case '0': case '\0':
            return "FILE";
        case '1':
            return "HARDLINK";
        case '2':
            return "SYMLINK";
        case '5':
            return "DIRECTORY";
        default:
            return "OTHER";
    }
}



int main(int argc, char** argv) {

    // GENERAL VARIABLES
    //count the types of all items
    std::map <std::string, uint> typecount{
        {"FILE", 0}, {"HARDLINK", 0}, {"SYMLINK", 0},
        {"DIRECTORY", 0}, {"OTHER", 0}
    };

    uint64_t sizeof_allfiles{}; // total size of all files in the archive
    std::string helptext
    {"usage: tarstats-pp [-h] [-j] [-f] tarfile.\n"
     "A tool to calculate basics statistics on tarball. Shamelessly inspired by github.com/isotopp/tarstats!\n\n"
     "mandatory argument:\n"
     "tarfile   a tarfile to calculate stats on\n\n"
     "optional arguments\n"
     "-h        this helptext\n"
     "-j        stats in JSON format printed to stdout\n"
     "-f        print stats to file <tarfilename>.txt or .json if -j invoked"};

    // Trivial check for arguments. Errorprone and has to be changed.
    if (argc < 2) {
        std::cout << helptext << '\n';
        return 9;
    }
    // Getting name from argument lists on startup. Trivial and errorprone. Placeholder for now.
    std::string archiveFilename(argv[1]);

    //Open tar File.
    std::ifstream file(archiveFilename, std::ios::binary);
    if(!file) {
        std::cout << "Error opening file" << std::endl;
        std::cout << helptext << '\n';
    }

    // Tar spec is working with continous 512 byte size blocks. Header is 512 bytes.
    int buffersize = 512;
    while (file) {
        //Read header of first item in tar archive
        char *headbuffer = new char[buffersize];
        file.read(headbuffer, buffersize);

        // tar file ends with 2 512byte blocks of 0. As no block should ever be 0 unless at the end, we check only once.
        if (eof(headbuffer)) {
            break;
        }

        // Read type of item
        std::string itemtype{};
        itemtype = getitemtype(headbuffer[156]);
        typecount[itemtype] += 1;


        // read itemsize and add to total
        sizeof_allfiles += getitemsize(headbuffer);

        // ignore file content. we want to get to the next header. item types != FILE have no content blocks (0 byte)
        if (getitemsize(headbuffer)!=0) {
            file.ignore((getitemsize(headbuffer) / 512) * 512 + 512);
        }

        // empty the headerbuffer
        delete[] headbuffer;
    }

    std::cout << sizeof_allfiles << std::endl;

    return 0;
}