Question

Know this might be rather basic, but I been trying to figure out how to one after create a dynamic array such as

double* data = new double[size];

be used as a source of data to be kept in to a binary file such as

ofstream fs("data.bin",ios:binary");
fs.write(reinterpret_cast<const char *> (data),size*sizeof(double));

When I finish writing, I attempt to read the file through

double* data = new double[size];
ifstream fs("data.bin",ios:binary");
fs.read(reinterpret_cast<char*> (data),size*sizeof(double));

However I seem to encounter a run time error when reading the data. Do you guys have any advice how i should attempt to write a dynamic array using pointers passed from other methods to be stored in binary files?

Answer 1

1. Hy:)

If you use Unix you have some functions:    int read(int fd, void

*buf, int count);. int write (int fd, void *buf, int nbytes);.

The functions are verry fast because
are kernel-functions.

i run your code and everything was
ok : 

      1 #include <iostream>
      2 #include <fstream>
      3 #include <cstring>
      4 using namespace std;
      5 
      6 int main()
      7 {
      8     double * s;
      9     int ns = 10;                    //information
     10     s = new double[ns];
     11 
     12     for (int i = 0 ; i < ns ; ++i)
     13         s[i] = 17*i + 23;           // i put my information here
     14 
     15     ofstream os("data.txt", ios::binary);
     16     os.write(reinterpret_cast<const char*> (s), sizeof(double) * ns);
     17     os.close();
     18 
     19     double * final;
     20     final = new double[ns];
     21 
     22     ifstream is("data.txt", ios::binary);
     23     is.read(reinterpret_cast<char *>(final), sizeof(double) * ns);
     24     is.close();
     25 
     26     for (int i=0; i < ns; ++i)
     27         cout<<s[i]<<" "<<final[i]<<"\n";
     28 
     29     return 0;
     30 }

~            

none@Brusture:~/Desktop$ g++ -o test
test.cpp  none@Brusture:~/Desktop$
./test  23 23 40 40 57 57 74 74 91
91 108 108 125 125 142 142 159 159
176 176