Instream & outstream

Question

So when you reading a file, char by char, how can you use a void function to remove all the white-space? How about at the start and at the end of the text.

Purpose: remove white-space
“Test1.dat” input file text
“ Hello World 123 4567 “
“translated.dat” output file support to be
“Hello World 123 4567” no space at begin and end

#include <iostream>
#include <fstream>
using namespace std;

void remove_blanks(ifstream& in_stream);

int main() {
const char INFILE[] = "test1.dat";
const char OUTFILE[] = "translated.dat";
char next; // get next char in file

// setup input file stream
fin.open(INFILE);
if (fin.fail()) {
cout << "Cannot open file\n";
exit(1);
}

// setup output file stream
ofstream fout;
fout.open(OUTFILE);
if (fout.fail()) {
cout << "Input file cannot be opened\n";
exit(1);
}

fin.get(next);
while (! fin.eof()) {
if (isspace(next)) {
remove_blanks(fin);
}
fout.put(next);
fin.get(next);
} // end of file loop

cout << "End of editing files.\n"
<< "Check translated.dat for result!" << endl;
// close streams
fin.close();
fout.close();
return 0;
}

void remove_blanks(ifstream& in_stream) {
char symbol;
in_stream.get(symbol);
while (isspace(symbol)) {
in_stream.get(symbol);
}
in_stream.putback(symbol); //error here it keep loop back to put back last char so file can’t end of file
return;

Answer 1

I'm not well versed with I/o streams, but I'll try. I think in your function, you may be trying to rearrange the input stream (which might be a bad idea, because output streams is where the output goes).

I think a simpler approach might do well. Test if the next char is a redundant space, if so, continue on. Else, put that char to the ofstream. To test it, it appears you allow only one space between words. You can set up a counter to keep track of the number of successive spaces found and reset it once it is > 1.

You might not need to have a function after all, but having one that takes an ifstream and a ofstream (and an optional length requirement to specify when to stop) might be nice.