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

Question

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

Answer 1

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

Answer 2

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;
}

Answer 3

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?

Answer 4

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.

Answer 5

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.