How do you save a whole array to a disk in c++

I've been looking, but i've never been able to save anything other than one coordinate in a 开发者_StackOverflow社区2 dimensional array

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This is called serialization. Have a look at this question for more info on using Boost to do just that.

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Based on StackedCrooked's idea, here's a solution that allows you to user either a C-style array of std::vector or any other sequence whose elements have << defined for them.

#include <cstddef>
#include <fstream>
#include <iostream>


// Beware, brain-compiled code ahead! 
template<class InpIt>
void save_seq(const std::ostream& os, InpIt begin, InpIt end)
{
    if(begin != end)
        os << *begin++;
    while(begin != end)
        os << ' ' << *begin++;
}

template<class OutpIt>
bool load_seq(const std::istream& is, OutpIt begin, std::size_t n)
{
    for( std::size_t i=0; is && i<n; ++i)
        is >> *begin++
    return is.good() || is.eof();
}
template<class OutpIt>
bool load_seq(const std::istream& is, OutpIt begin)
{
    while(is.good())
        is >> *begin++
    return is.eof();
}

template<class T, std::size_t N>
void save_array(const std::ostream& os, const T (&data)[N])
{
    save_seq(os, data, data+N);
}


template<class T, std::size_t N>
bool load_array(const std::istream& is, T (&data)[N])
{
    return load_seq(is, data, N);
}

int main()
{
    const std::size_t size = 5;
    int numbers[size];
    numbers[0] = 10;
    numbers[1] = 11;
    numbers[2] = 12;
    numbers[3] = 13;
    numbers[4] = 14;
    {
        std::oftsream ofs("array.txt");
        if(!ofs.good())
            return 1;
        save_array(ofs, numbers);
    }
    {
        std::iftsream ifs("array.txt");
        if(!ifs.good())
            return 2;
        int test[size];
        load_array(ifs, test);
        for (std::size_t idx = 0; idx < size; ++idx)
            std::cout << "test[" << idx << "]: " << test[idx] << std::endl;
    }

    std::vector<int> numbers2;
    numbers2.push_back(20);
    numbers2.push_back(21);
    numbers2.push_back(22);
    numbers2.push_back(23);
    {
        std::oftsream ofs("array.txt");
        if(!ofs.good())
            return 1;
        save_Seq(ofs, numbers2.begin(), numbers2.end());
    }
    {
        std::iftsream ifs("array.txt");
        if(!ifs.good())
            return 2;
        std::vector<int> test;
        load_seq(ifs, std::back_inserter(test));
        for (std::size_t idx = 0; idx < numbers2.size(); ++idx)
            std::cout << "test[" << idx << "]: " << test[idx] << std::endl;
    }

    return 0;
}

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You could use a std::fstream or boost::serialization. Your question is a bit vague, so I'm not entirely sure what it is you want, need?

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If the array contains flat data (i.e., data that does not include pointers to other data), you can write an entire array in a single write to a file.

Without any idea what your data looks like, it would not be possible to say much more about it.

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After some tinkering I came up with this:

#include <cstddef>
#include <fstream>
#include <iostream>


template<class T>
void SaveArray(const std::string & file, T * data, std::size_t length)
{
    std::ofstream out(file.c_str());
    for (std::size_t idx = 0; idx < length; ++idx)
    {
        if (idx != 0)
        {
            out << " ";
        }
        out << *data++;
    }
}


template<class T>
std::size_t LoadArray(const std::string & file, T * data, std::size_t length)
{
    std::ifstream in(file.c_str());
    std::size_t count = 0;
    while (count++ < length && in >> *data++);
    return count - 1; // return number of items
}


int main()
{
    int numbers[5];
    numbers[0] = 10;
    numbers[1] = 11;
    numbers[2] = 12;
    numbers[3] = 13;
    numbers[4] = 14;
    SaveArray("array.txt", &numbers[0], 5);

    int test[5];
    LoadArray("array.txt", &test[0], 5);

    for (std::size_t idx = 0; idx < 5; ++idx)
    {
        std::cout << "test[" << idx << "]: " << test[idx] << std::endl;
    }
    return 0;
}

Suggestions for improvement are welcome.