Reading and writing a std::vector into a file correctly

Question

That is the point. How to write and read binary files with std::vector inside them?

I was thinking something like:

//============ WRITING A VECTOR INTO A FILE ================ const int DIM = 6; int array[DIM] = {1,2,3,4,5,6}; std::vector<int> myVector(array, array + DIM); ofstream FILE(Path, ios::out | ofstream::binary); FILE.write(reinterpret_cast<const char *>(&myVector), sizeof(vector) * 6); //=========================================================== 

But I don't know how to read this vector. Because I thought that the following was correctly but it isn't:

ifstream FILE(Path, ios::in | ifstream::binary); FILE.read(reinterpret_cast<const char *>(&myVector), sizeof(vector) * 6); 

So, how to perform the operation?

Answer 1

Try using an ostream_iterator/ostreambuf_iterator, istream_iterator/istreambuf_iterator, and the STL copy methods:

#include <algorithm> #include <iostream> #include <iterator> #include <vector>  #include <fstream> // looks like we need this too (edit by π)  std::string path("/some/path/here");  const int DIM = 6; int array[DIM] = {1,2,3,4,5,6}; std::vector<int> myVector(array, array + DIM); std::vector<int> newVector;  std::ofstream FILE(path, std::ios::out | std::ofstream::binary); std::copy(myVector.begin(), myVector.end(), std::ostreambuf_iterator<char>(FILE));  std::ifstream INFILE(path, std::ios::in | std::ifstream::binary); std::istreambuf_iterator iter(INFILE); std::copy(iter.begin(), iter.end(), std::back_inserter(newVector)); 

Answer 2

Use boost::serialization.

If you don't want use boost - write size and vector.

size_t sz = myVector.size(); FILE.write(reinterpret_cast<const char*>(&sz), sizeof(sz)); FILE.write(reinterpret_cast<const char*>(&myVector[0]), sz * sizeof(myVector[0]));