storing text to string from a file that contains spaces - c++

Question

So I've been doing algorithms in C++ for about 3 months now as a hobby. I've never had a problem I couldn't solve by googleing up until now. I'm trying to read from a text file that will be converted into a hash table, but when i try and capture the data from a file it ends at a space. here's the code
#include <iostream>
#include <fstream>
int main()
{
using namespace std;
ifstream file("this.hash");
file >> noskipws;
string thing;
file >> thing;
cout << thing << endl;
return 0;
}
I'm aware of the noskipws flag i just don't know how to properly implement it

Answer 1

When using the formatted input operator for std::string it always stops at what the stream considers to be whitespace. Using the std::locale's character classification facet std::ctype<char> you can redefine what space means. It's a bit involved, though.
If you want to read up to a specific separator, you can use std::getline(), possibly specifying the separator you are interested in, e.g.:
std::string value;
if (std::getline(in, value, ',')) { ... }
reads character until it finds a comma or the end of the file is reached and stores the characters up to the separator in value.
If you just want to read the entire file, one way to do is to use
std::ifstream in(file.c_str());
std::string all((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());

Answer 2

I think the best tool for what you're trying to do is get, getline or read. Now those all use char buffers rather than std::strings, so need a bit more thought, but they're quite straightforward really. (edit: std::getline( file, string ), as pointed out by Dietmar Kühl, uses c++ strings rather than character buffers, so I would actually recommend that. Then you won't need to worry about maximum line lengths)
Here's an example which will loop through the entire file:
#include <iostream>
int main () {
char buffer[1024]; // line length is limited to 1023 bytes
std::ifstream file( "this.hash" );
while( file.good( ) ) {
file.getline( buffer, sizeof( buffer ) );
std::string line( buffer ); // convert to c++ string for convenience
// do something with the line
}
return 0;
}
(note that line length is limited to 1023 bytes, and if a line is longer it will be broken into 2 reads. When it's a true newline, you'll see a \n character at the end of the string)
Of course, if you a maximum length for your file in advance, you can just set the buffer accordingly and do away with the loop. If the buffer needs to be very big (more than a couple of kilobytes), you should probably use new char[size] and delete[] instead of the static array, to avoid stack overflows.
and here's a reference page: http://www.cplusplus.com/reference/fstream/ifstream/