using fstream to read every character including spaces and newline

Question

I wanted to use fstream to read a txt file.

I am using inFile >> characterToConvert, but the problem is that this omits any spaces an

Answer 1

Probably the best way is to read the entire file's contents into a string, which can be done very easily using ifstream's rdbuf() method:

std::ifstream in("myfile");

std::stringstream buffer;
buffer << in.rdbuf();

std::string contents(buffer.str());

You can then use regular string manipulation now that you've got everything from the file.

While Tomek was asking about reading a text file, the same approach will work for reading binary data, though the std::ios::binary flag needs to be provided when creating the input file stream.

Answer 2

I also find that the get() method of ifstream object can also read all the characters of the file, which do not require unset std::ios_base::skipws. Quote from C++ Primer:

Several of the unformatted operations deal with a stream one byte at a time. These operations, which are described in Table 17.19, read rather ignore whitespaces.

These operations are list as below: is.get(), os.put(), is.putback(), is.unget() and is.peek().

Below is a minimum working code

#include <iostream>
#include <fstream>
#include <string>

int main(){
    std::ifstream in_file("input.txt");

    char s;

    if (in_file.is_open()){
        int count = 0;
        while (in_file.get(s)){

            std::cout << count << ": "<< (int)s <<'\n';
            count++;
        }

    }
    else{
        std::cout << "Unable to open input.txt.\n";
    }
    in_file.close();

    return 0;
 }

The content of the input file (cat input.txt) is

ab cd
ef gh

The output of the program is:

0: 97
1: 98
2: 32
3: 99
4: 100
5: 10
6: 101
7: 102
8: 32
9: 103
10: 104
11: 32
12: 10

10 and 32 are decimal representation of newline and space character. Obviously, all characters have been read.

Answer 3

For encryption, you should probably use read(). Encryption algorithms usually deal with fixed-size blocks. Oh, and to open in binary mode (no translation frmo \n\r to \n), pass ios_base::binary as the second parameter to constructor or open() call.

Answer 4

I haven't tested this, but I believe you need to clear the "skip whitespace" flag:

inFile.unsetf(ios_base::skipws);

I use the following reference for C++ streams: IOstream Library

Answer 5

A lot of the benefit of the istream layer is providing basic formatting and parsing for simple types ro and from a stream. For the purposes that you describe, none of this is really important and you are just interested in the file as a stream of bytes.

For these purpose you may be better of just using the basic_streambuf interface provided by a filebuf. The 'skip whitespace' behaviour is part of the istream interface functionality that you just don't need.

filebuf underlies an ifstream, but it is perfectly valid to use it directly.

std::filebuf myfile;
myfile.open( "myfile.dat", std::ios_base::in | std::ios_base::binary );

// gets next char, then moves 'get' pointer to next char in the file
int ch = myfile.sbumpc();

// get (up to) the next n chars from the stream
std::streamsize getcount = myfile.sgetn( char_array, n );

Also have a look at the functions snextc (moves the 'get' pointer forward and then returns the current char), sgetc (gets the current char but doesn't move the 'get' pointer) and sungetc (backs up the 'get' pointer by one position if possible).

When you don't need any of the insertion and extraction operators provided by an istream class and just need a basic byte interface, often the streambuf interface (filebuf, stringbuf) is more appropriate than an istream interface (ifstream, istringstream).

Answer 6

Simple

#include <fstream>
#include <iomanip>


ifstream ifs ("file");
ifs >> noskipws

that's all.