Чтение слов из текстового файла и замена этими словами названий переменных в других файлах (оптимизация)

#include <iostream>
using namespace std;
using namespace System;
using namespace System::IO;
using namespace System::Text;
 
String* insertChar(String *data, int loc, String *replacement, int i) {
    return data->Insert(loc, replacement->Substring(i, 1));
}
 
String* replace_word(String* data, int loc, int length, String* replacement) {
    // delete the pattern string from loc:
    data = data->Remove(loc, length);
    // insert each character of the replacement string:
    for (int i = 0; i < replacement->Length; i++) {
        data = insertChar(data, loc+i, replacement, i);
        // data->Insert(loc + i, replacement->Substring(i, 1));
    }
    return data;
}
 
String* string_subst(String *data, String *pattern, String *replacement) {
    try {
            int loc;
            // find every occurrence of pattern:
            [I]for (loc = data->IndexOf(pattern, 0); loc >= 0;
                loc = data->IndexOf(pattern, 0)) {[/I]
                // replace word
                data = replace_word(data, loc, pattern->Length, replacement);
            }   
            return data;
    } catch (Exception *e) {
        Console::WriteLine("Error in substitute ");
        Console::WriteLine(e->ToString());
        return data;
    }
}
 
 
String* batch_subst(String *data, const char* subs_filename) {
    try {
        String *subs_file = new String(subs_filename);
        StreamReader *subs_reader = new StreamReader(subs_file);
        String *pattern, *replacement, *separator;
        while (subs_reader->Peek() >= 0) {
            pattern = subs_reader->ReadLine();
            replacement = subs_reader->ReadLine();
            separator = subs_reader->ReadLine();
            data = string_subst(data, pattern, replacement);
        }
        return data;
    } catch(Exception* e ) {
        Console::WriteLine( "Error in do_substitutions ");
        Console::WriteLine( e->ToString());
        return data;
    }
}
 
void process_file(const char* filename, const char* subs_filename) {
    StreamReader *reader;
    StreamWriter *writer;
    String *file = new String(filename);
    try {
        reader = new StreamReader( file );
        String *data = reader->ReadToEnd();
        data = batch_subst(data, subs_filename);
        reader->Close();
        // write the data
        writer = new StreamWriter(file, false);
        writer->Write(data);
        writer->Close();
    }  catch(Exception* e) {
        Console::WriteLine( "Error while processing file ");
        Console::WriteLine( e->ToString());
    }
}
 
int main(int argc, char *argv[]) {  
    if (argc < 3) {
        cout << "Not enough input arguments" << endl;
        cout << "Usage: substitute subs-file src1 src2 ..." << endl;
    } else {
 
        for (int i = 2; i < argc; i++) {
            process_file(argv[i], argv[1]);
        }
    }
    return 0;
}