File_CW01_v3.cpp

/*
Дан файл f, компоненты которого являются целыми числами.
Число компонент файла делится на 2n.
Записать в файл g наибольшее значение первых 2n компонент файла f, затем следующих 2n и т.д.
*/

#include <iostream>
#include <fstream>

using namespace std;

void readFileData(ifstream &f, char fileName[20]);
void writeFileData(ofstream &f, char fileName[20]);
void calculateFileData(ifstream &iFile, ofstream &oFile, char sourceFileName[20], char resultFileName[20]);

int n;

int main()
{
    char sourceFileName[20], resultFileName[20], action;
    ifstream iFile;
    ofstream oFile;

    cout << "Please enter surce file name: ";
    cin >> sourceFileName;
    cout << "Please enter result file name: ";
    cin >> resultFileName;
    cout << "Please enter n: ";
    cin >> n;

restartMark:
    cout << "Read source (r). Write source (w). Calculate (c). Read result (d). Exit (e). ? ";
    cin >> action;

    switch (action) {
    case 'r':
    case 'R':
        readFileData(iFile, sourceFileName);
        break;
    case 'w':
    case 'W':
        writeFileData(oFile, sourceFileName);
        break;
    case 'c':
    case 'C':
        calculateFileData(iFile, oFile, sourceFileName, resultFileName);
        break;
    case 'd':
    case 'D':
        readFileData(iFile, resultFileName);
        break;
    default:
        return 0;
    }

    goto restartMark;

    return 0;
}

void readFileData(ifstream &f, char fileName[20])
{
    int element, i = 0;

    cout << "Reading file \"" << fileName << "\":" << endl;

    f.open(fileName, ios::binary | ios::in);

    if (f.is_open()) {
        if (f.eof()) {
            f.clear();
            f.seekg(0);
        }

        while (f.read((char *)&element, sizeof element)) {
            cout << ++i << ") " << element << endl;
        }

        f.close();
    }
    else {
        cout << "An error ocured while reading file." << endl;
    }
}

void writeFileData(ofstream &f, char fileName[20])
{
    char action = 'n';
    int i, j, element;

    cout << "Writing file \"" << fileName << "\":" << endl;

    f.open(fileName, ios::binary | ios::out);

    if (f.is_open()) {
        while (action != 'y' && action != 'Y') {
            for (i = 0; i < 2; i++) {
                for (j = 0; j < n; j++) {
                    cout << "Enter element (int): ";
                    cin >> element;
                    f.write((char *)&element, sizeof element);
                }
            }
            cout << "Do you want to stop entering numbers? (y/n) ";
            cin >> action;
        }

        f.close();
        cout << "File \"" << fileName << "\" successfully writed." << endl;
    }
    else {
        cout << "An error ocured while writing file." << endl;
    }
}

void calculateFileData(ifstream &iFile, ofstream &oFile, char sourceFileName[20], char resultFileName[20])
{
    int element, i = 0, max = -100000;

    cout << "Reading file \"" << sourceFileName << "\":" << endl;

    iFile.open(sourceFileName, ios::binary | ios::in);
    oFile.open(resultFileName, ios::binary | ios::out);

    if (iFile.is_open() && oFile.is_open()) {
        if (iFile.eof()) {
            iFile.clear();
            iFile.seekg(0);
        }

        while (iFile.read((char *)&element, sizeof element)) {
            if (i == 0 || element > max) {
                max = element;
            }
            i++;
            if (i == 2 * n) {
                oFile.write((char *)&max, sizeof element);
                i = 0;
            }
        }

        iFile.close();
        oFile.close();
        cout << "File \"" << resultFileName << "\" successfully writed." << endl;
    }
    else {
        cout << "An error ocured while opening file." << endl;
    }
}