read line of string to array of chars

[ekailan]

I am reading a file line by line I need to copy the line which is string to array of chars named packet.

what function could help me do that.
this is my code:

char *packet;
packet=new char [1000000];
ifstream  inFile2;
string t, line;
cout<<"Enter a file name.\n";
    cin>>t;
    inFile2.open(f.c_str());
       if ( !inFile2 )
       {
          cout<<"Unable to open file. Enter a different name: ";
          inFile2.clear();
          cin >> t;
          inFile2.open(t.c_str());
 
       }
        while(!inFile2.eof())
        {
 
 
      getline(inFile2, line);
 
//how to copy line to the array packet???
 
 
 
      }
 
 

[weaknessforcats]

Just create a string object an assign the packet to the object.

string data;
data= packet;

[ekailan]

thank you for your reply

I need to copy the string to the array "packet"

[Banfa]

If you really need to do that then use std::copy from the algorithms library however weaknessforcats question is why don't you just make packet a std::string then you can simply

packet = line;
 

Even if you do not want it to be a std::string then it should at the very least be a std::vector rather than a C array in which case you could use std::vector::insert.

[ekailan]

I cant use any other declaration for the "packet", because its input for another algorithm ...I will try to read a bout "std::copy ".


Thanks

[ekailan]

I modified the code to this, but I get this error
" out of memory".after three iteration of excution.

char *packet; 
packet=new char [1000000]; 
ifstream  inFile2; 
string t, line; 
cout<<"Enter a file name.\n"; 
    cin>>t; 
    inFile2.open(t.c_str()); 
       if ( !inFile2 ) 
       { 
          cout<<"Unable to open file. Enter a different name: "; 
          inFile2.clear(); 
          cin >> t; 
          inFile2.open(t.c_str()); 
 
       } 
        while(!inFile2.eof()) 
        { 
 
 
      getline(inFile2, line); 
 
strcpy_s(packet, 500, line.c_str()); 
 
 

[Banfa]

If the other algorithm expects a new'd char buffer that it then frees itself this is true (although it speaks of poor design of the other algorithm).

If you just need to pass a char * or const char * and you handle the delete yourself then this is not true. You can use a std::vector which has the same memory footprint as an array, i.e. this is valid

void function(const char *data);
 
char *pointer = new char[50];
 
std::vector<char> vec(50);
 
function(pointer);
function(&pointer[0]);
function(&vec[0]);
 

Allocating 1000000 bytes to packet seems extremely poor as is copying 500 bytes out of line. All of these sizes can be based on std::string::size to get the actual size required.

"out of memory"

Do you ever free the memory allocated to packet or do you just keep on allocating more? Memory allocation needs to be handled carefully which is why you should try to minimise it where possible or better still hand it off to code that handles it for you like std::vector.