C++ replace words in a string (text file)

Question

so I worked on my program and now I am on a point where I can not find a solution. I need to replace some more signs in the fext file, for now the program only replaces "TIT" with the code number "*245$a", if I want to replace other letters the same way, the program does not change. Does anybody know how I can implement some more replacements in the text file? Let me know if there is a better option to replace more than 5 signs with another ones. Thank you

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


int main()
{

    char dateiname[64], kommando[64];

    ifstream iStream;

    cout << "Choose an activity" << endl <<
    " s - search " << endl <<
    " c - convert" << endl <<
    " * - end program" << endl;
    cin.getline(kommando,64,'\n');
    switch(kommando[0])
    {
        case 'c':
            cout << "Enter a text file!" << endl;
            cin.getline(dateiname,64,'\n');
            iStream.open("C://users//silita//desktop//schwarz.txt");

        case 's':
            break;
        case '*':
            return 0;
        default:
            cout << "I can not read " << kommando << endl;
    }

    if (!iStream)
    {
        cout << "The File" << dateiname << "does not exist." << endl;
    }

    string s;
    char o[] = "TIT";
    while (getline(iStream, s))
    {
        while(s.find(o, 0) < s.length())
            s.replace(s.find(o, 0), s.length() - s.find(o, 3),"*245$a");

        cout << s << endl;
    }

    iStream.close();
}

Answer 1

You can use map in C++ STL to store multiple convert rules:

#include<map>
#include<algorithm>
using namespace std;

map<string,string> convertRules;
typedef map<string,string>::iterator MIT;

void setConvertRules(int numOfRules){
    string word,code;
    for(int i = 0 ; i < numOfRules; ++i){
        cin>>word>>code;

        //Use code as search key in order to decrypt
        //If you want to encrypt, use convertrules[word] = code;
        convertRules[code] = word;
    }
}

To convert a file, just do as follows (some functions and classes need to be declared and implemented first, but here we mainly focus on top-level design):

/* Detailed class implementations are omitted for simplicity */

//a class to store contents of a file
class File;

//a processor to read, insert and overwrite certain file
class FileProcessor;

void FileProcessor::convert(const string &code, const string &word){
    cursor == file.begin();
    while(cursor != fp.end()){
         _fp.convertNextLine(code,word);
    }
}

File file;
FileProcessor filePcr;

int main()

    const string sourceDir = "C://users//silita//desktop//schwarz.txt";
    const string destDir = "C://users//silita//desktop//schwarz_decrypted.txt";

    //Open a .txt file and read in its contents
    if (!file.openAndReadIn(sourceDir)){
        cerr << "The File" << sourceDir << "does not exist." << endl;
        abort();
    }

    //Try to link processor to open file
    if(!fp.linkTo(file)){
        cerr << "Access to file" << sourceDir << "is denied." << endl;
        abort();
    }

    //iterator is like a more safe version of C-style pointer
    //the object type is a string-string pair
    for(MIT it = convertRules.begin(); it != convertRules.end(); ++it){
        fp.convert(it->first, it->second);
    }

    file.saveAs(destDir);
    return 0;
}

Finally, if I would suggest you use C-style strstr function for efficiency when dealing with large files or batch processing. string::find adopts a naive sequential search startegy while strstr is implemented with the famous KMP algorithm for fast pattern match in strings , which is both efficient and thorough(can replace all matchs in one go instead of another for-loop).