Converts Cave Story TSC files to plaintext files and back

tsc.cpp

/*
TSC Converter v1.0
A command-line program that converts Cave Story TSC files to plaintext files and back
Created by FDeityLink
Released under public domain

-- Must be compiled with the C++11 standard --

Instructions for use:
    -Supply a file directory as an argument or in the program itself - the program auto-detects format and converts accordingly.
        -If the filedir has spaces, you needn't put it in quotes (unless it's an argument)
        -If you do it as an argument, then you can put in as many file directories as you wish 
            -However, this does not work for files given in the program itself
    -If you wish to exit, type "exit"

TSC File Format Notes:    
    Encoding char is the middle character in file: char at floor(file size / 2)
        ex: size of 313 bytes, encode char is at 156th byte

    Newlines are Windows-style newlines ("\r\n"): 0x0D + encode char val, then 0x0A + encode char val
        - Because they're Windows-style newlines, open your files in binary mode, not text, otherwise the following transformations are done, which will end up corrupting the file
	    - '\r\n' --> "\n" for input
	    - '\n' --> "\r\n" for output

    All characters in the file except for the encoding char itself (so other copies of the character are still encoded) have the value of the encoding char added to them when saved
    ex: encoding char = [space]: only that instance of the [space] character will not be encoded, but the others will

    When reading a TSC file, subtract the encoding character from each character (except the encoding char itself, as noted above) to properly decode the file
    When writing a TSC file, add the encoding character to each character (except the encoding char itself, as noted above) to properly encode the file
*/

#include <iostream>
#include <string>
#include <fstream>
#include <algorithm> //std::remove(ForwardIterator first, ForwardIterator last, const T& val)
#include <cstdio> //remove(const char* filename)

#define EXTENSION_LENGTH 4

int main(const int argc, const char* argv[]) {
    using namespace std;

    if (argc < 1) { //signed int, possible error with it holding zero or a negative value
        throw out_of_range("Argument count must be greater than or equal to 1 (including executable name). Try again.");
    }

    cout << "TSC Converter v1.0" << endl;
    cout << "Created by F_Deity_Link\n" << endl;

    for (int i = 1;;) {
        //Parsing input and setting up variables for later
        string originalDir;
        if (i < argc) {
            originalDir = argv[i++];
            cout << originalDir << endl;
        }
        else {
            cout << "Enter the path of a TSC or text file you wish to convert, or type \"exit\" to quit" << endl;
            while ("" == originalDir) {
                getline(cin, originalDir);
            }
        }

        if (string("exit") == originalDir) {
            return 0;
        }

        originalDir.erase(std::remove(originalDir.begin(), originalDir.end(), '\"'), originalDir.end()); //takes out quote marks
                            //std::remove to ensure no conflict with remove(), which deletes a file
        bool originalIsTscFile = false;
        string convertedExtension = ".tsc";
        if (originalDir.length() >= EXTENSION_LENGTH) { //if length < EXTENSION_LENGTH, std::out_of_range thrown when passing (str.length() - EXTENSION_LENGTH) to compare()
            if (originalDir.compare(originalDir.length() - EXTENSION_LENGTH, EXTENSION_LENGTH, string(".tsc")) == 0) {
                originalIsTscFile = true;
                convertedExtension = ".txt";
            }
            else if (originalDir.compare(originalDir.length() - EXTENSION_LENGTH, EXTENSION_LENGTH, string(".txt")) != 0) {
                cerr << "ERROR: Unsupported file type\n" << endl;
                continue;
            }
        }
        else {
            cerr << "ERROR: Unsupported file type\n" << endl;
            continue;
        }

        //Opening files
        ifstream originalFile(originalDir, ifstream::binary | ifstream::ate); //ate (at end) starts at end (so I don't need to seek before finding encoder pos)
        if (!originalFile) {
            cerr << "ERROR: Could not open file \"" << originalDir << "\"\n" << endl;
            continue;
        }

        string convertedDir = originalDir;
        convertedDir.replace(convertedDir.length() - EXTENSION_LENGTH, EXTENSION_LENGTH, convertedExtension); //change the extension
        ofstream convertedFile(convertedDir, ofstream::binary | ofstream::trunc);
        if (!convertedFile) {
            cerr << "ERROR: Could not open file \"" << convertedDir << "\"\n" << endl;
            continue;
        }

        //Converting the file
        cout << "Converting \"" << originalDir << "\" and writing it out to \"" << convertedDir << "\"" << endl;

        const int encoderCharPos = originalFile.tellg() / 2; //integer division, will truncate decimal
        originalFile.seekg(encoderCharPos);
        unsigned char encoderChar;
        originalFile >> noskipws >> encoderChar;
        if (originalIsTscFile) { //subtract to decode, add to encode
            encoderChar *= -1;
        }
        originalFile.seekg(0, ios_base::beg);

        for (unsigned char c; originalFile >> noskipws >> c;) {
            if (encoderCharPos + 1 != originalFile.tellg()) {
                c += encoderChar;
            }
            convertedFile << c;
        }

        if (originalFile.bad() || convertedFile.bad()) {
                cerr << "ERROR: An error occurred with converting \"" << originalDir << "\" to \"" << convertedDir << "\". Please try again\n" << endl;
                convertedFile.close();
                remove(convertedDir.c_str());
        }
        else {
            cout << "\"" << originalDir << "\" was converted to \"" << convertedDir << "\"\n" << endl;
        }
    }
    return 0;
}