PoE particle remover

/**
* removes all particle / emitter durations from Content.ggpk (Path Of Exile)
* creates new file, renames old .ggpk to .bak*
*
* code isn't optimized at all, but works fine.
* 2014-12-21.
*
*/

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

using namespace std;

//========================================

inline bool isFileExists (const string& name) {
    if (FILE *file = fopen(name.c_str(), "r")) {
        fclose(file);
        return true;
    } else {
        return false;
    }
}

//========================================

const int CHARCODE_PREV_0 = 0x2F;
const int CHARCODE_AFTER_9 = 0x3A;
const int CHARCODE_POINT = 0x2E;
const int CHARCODE_SPACE = 0x20;

/**
* changes strings like "var 1" -> "var 0", "var 23.456" -> "var 00.000" etc where '0' == param var.
*
* @param line - string for replacement.
* @param varName - finding string. next symbols will be replaced to param var if they're digital.
* @param var - new var symbol.
* @param offset - skip symbols before var position.
* @param multivars - if there're can be few vars. i.e. with multivars = true and var = "0": "someparam 1 2.2 3" -> "someparam 0 0.0 0".
*/
void replaceStringVar(string& line, const string& varName, const string& var, int offset = 0, bool multivars = true) {
        //unicode.
        size_t linePos = 0;
        size_t lineLen = line.length();
        size_t varNameLen = varName.length();
        size_t newVarPos = 0;
        int oldVar = 0;
        bool next = true;
        size_t varNum = 0;
        while((linePos = line.find(varName, linePos)) != string::npos) {
            next = true;
            varNum = 0;
            while (next) {
                newVarPos = linePos + varNameLen + offset + varNum;
                if (newVarPos < lineLen) {
                    oldVar = int(line[newVarPos]);
                    if (oldVar > CHARCODE_PREV_0 && oldVar < CHARCODE_AFTER_9) {
                        line.replace(newVarPos, 1, var);
                    } else if (oldVar == CHARCODE_POINT) {
                        //skip
                    } else if (oldVar == CHARCODE_SPACE) {
                        if (!multivars) {
                            next = false;
                        }
                    } else {
                        next = false;
                    }
                } else {
                    break;
                }
                varNum += 2; //unicode.
            }
            linePos += varNameLen;
        }
}

//========================================

/** not really, it's just converting. don't use wstring. */
string ansiToUnicode(string& line) {
    const char cNull = 0x00;
    string ret = "";
    int len = line.length();
    for (int i = 0; i < len; i++) {
        //actually it must be first \0, then char but it's easier to replace the next symbol, not the next+1
        ret += line[i];
        ret += cNull;
    }
    return ret;
}

//========================================

int main() {
    string fIn = "Content.ggpk";

    string fOut = fIn + "_repl.tmp";
    const string replVar = "0";

    //todo: make array
    string sAnsiPD1 = "particle_duration ";
    string sRepl1 = ansiToUnicode(sAnsiPD1);

    string sAnsiPD2 = "particle_duration_variance ";
    string sRepl2 = ansiToUnicode(sAnsiPD2);

    string sAnsiPD3 = "particles_per_second ";
    string sRepl3 = ansiToUnicode(sAnsiPD3);

    string sAnsiPD4 = "emitter_duration ";
    string sRepl4 = ansiToUnicode(sAnsiPD4);


    //===

    const char charNewLine1 = 0x0A;
    string sNewLine;
    sNewLine = charNewLine1;

    ifstream inFile(fIn.c_str(), ifstream::binary);
    ofstream outFile(fOut.c_str(), ofstream::binary);
    //todo: check if everything is ok

    size_t iLine = 0;
    string line;

    bool isContinue = getline(inFile, line);

    if (isContinue) {
        cout<<"\nopened file: "<<fIn<<"\n";

        while (isContinue) {
            //iLine++;

            istringstream iss(line);

            replaceStringVar(line, sRepl1, replVar, 0, true);
            replaceStringVar(line, sRepl2, replVar, 0, true);
            replaceStringVar(line, sRepl3, replVar, 0, true);
            replaceStringVar(line, sRepl4, replVar, 0, true);

            outFile<<line;

            isContinue = getline(inFile, line);
            //todo: read bigger part of file for less i/o operations.
            if (isContinue) {
                outFile<<sNewLine;
            }
        }

        inFile.close();
        outFile.close();

        cout<<"replacement: done.\n";

        string defaultBak = fIn + ".bak";
        string newBak = "";
        bool renamed = false;
        for (char c = '0'; c < '6'; c++) {
            newBak = defaultBak + c;
            if (!isFileExists(newBak)) {
                int result = rename(fIn.c_str(), newBak.c_str());
                if (result == 0) {
                    cout<<"old file saved as: "<<newBak<<"\n";
                    result = rename(fOut.c_str(), fIn.c_str());
                    if (result == 0) {
                        cout<<"new file saved as: "<<fIn<<"\n";
                    }
                    renamed = true;
                    break;
                }
            }
        }
        if (!renamed) {
            cout<<"can't rename file: "<<fIn<<"\n to: "<<newBak<<"\n\nFile with replacements is: "<<fOut;
        }


    } else {
        cout<<"\nCan't open file.";
    }

    cout<<"\n.";
    char c[1024];
    cin>>c;
}