More concise way to load a raw string from a file c++

Question

Basically what I want to do is to load a string from a file that is to be encoded as a json.

The way I have achieved this is quite verbose for what should be a simple operation:

std::ifstream t(json_path);

std::string stringbuf = std::string(std::istreambuf_iterator<char>(t), std::istreambuf_iterator<char>());

boost::erase_all(stringbuf, "\t");

boost::erase_all(stringbuf, "\n");

boost::erase_all(stringbuf, " ");

Is there a briefer way to load a text file to a string and strip out the special characters?

Answer 1

You can also use std::copy_if and an inserting iterator to copy only the characters that you want instead of copying everything, shuffling the bytes around (eg, std::remove_if ), and removing the ones that you don't want.

#include <algorithm>
#include <fstream>
#include <iostream>
#include <iterator>
#include <string>


int
main(int argc, char **argv)
{
    std::string outbuf;
    std::ifstream ins(argv[1]);
    std::copy_if(std::istreambuf_iterator<char>(ins),
                 std::istreambuf_iterator<char>(),
                 std::back_insert_iterator<std::string>(outbuf),
                 [](char c) { return !std::isspace(c); });
    std::cout << outbuf << std::endl;
    return 0;
}

Answer 2

You can use std::getline and erase/remove idiom with a lambda (or functor, if you don't have C++11 support), like

std::string string_buf(std::istreambuf_iterator<char>(t), {});
string_buf.erase(std::remove_if(string_buf.begin(), string_buf.end(), 
        [](char c) { return std::isspace(c);}), 
        string_buf.end()
);

Answer 3

// Open the file
std::ifstream t(json_path);

// Initialize the string directly, no = sign needed.
// C++11: Let second istreambuf_iterator argument be deduced from the first.
std::string stringbuf(std::istreambuf_iterator<char>(t),  {});

// C++11: Use a lambda to adapt remove_if.
char ws[] = " \t\n";
auto new_end = std::remove_if( stringbuf.begin(), stringbuf.end(),
    []( char c ) { return std::count( ws, ws + 3, c ); } );

// Boost was doing this part for you, but it's easy enough.
stringbuf.erase( new_end, stringbuf.end() );

Answer 4

You can do that in that way:

inFile.open(fileName, ios::in); 

if(inFile.fail()) {
    cout<<"error opening the file.";
} else {
    getline(inFile,paragraph);
    cout << paragraph << endl << endl;
}

numWords=paragraph.length();

while (subscript < numWords) {
    curChar = paragraph.substr(subscript, 1);
    if(curChar==","||curChar=="."||curChar==")"
        ||curChar=="("||curChar==";"||curChar==":"||curChar=="-"
        ||curChar=="\""||curChar=="&"||curChar=="?"||
        curChar=="%"||curChar=="$"||curChar=="!") {
        paragraph.erase(subscript, 1);
        numWords-=1;
    } else {
        subscript+=1;
    }
}

cout<<paragraph<<endl;
inFile.close();