path: root/Bachelor/Prog2/Codebeispiele/4_ch14/Fig14_15.cpp

// Fig. 14.15: fig14_15.cpp

// This program reads a random access file sequentially, updates

// data previously written to the file, creates data to be placed

// in the file, and deletes data previously in the file.

#include <iostream>



using std::cout;

using std::cerr;

using std::cin;

using std::endl;

using std::ios;

using std::left;

using std::right;

using std::fixed;

using std::showpoint;



#include <fstream>



using std::ofstream;

using std::ostream;

using std::fstream;



#include <iomanip>



using std::setw;

using std::setprecision;



#include <cstdlib>

#include "clientData.h"  // ClientData class definition



int enterChoice();

void printRecord( fstream& );

void updateRecord( fstream& );

void newRecord( fstream& );

void deleteRecord( fstream& );

void outputLine( ostream&, const ClientData & );

int getAccount( const char * const );



enum Choices { PRINT = 1, UPDATE, NEW, DELETE, END };



int main()

{

   // open file for reading and writing

   fstream inOutCredit( "credit.dat", ios::in | ios::out );



   // exit program if fstream cannot open file

   if ( !inOutCredit ) {

      cerr << "File could not be opened." << endl;

      exit ( 1 );



   } // end if

   

   int choice;



   // enable user to specify action

   while ( ( choice = enterChoice() ) != END ) {



      switch ( choice ) {



         // create text file from record file

         case PRINT:

            printRecord( inOutCredit );

            break;



         // update record

         case UPDATE:

            updateRecord( inOutCredit );

            break;



         // create record

         case NEW:

            newRecord( inOutCredit );

            break;



         // delete existing record

         case DELETE:

            deleteRecord( inOutCredit );

            break;



         // display error if user does not select valid choice

         default:

            cerr << "Incorrect choice" << endl;

            break;



      } // end switch



      inOutCredit.clear(); // reset end-of-file indicator



   } // end while



   return 0;



} // end main



// enable user to input menu choice

int enterChoice()

{

   // display available options

   cout << "\nEnter your choice" << endl

        << "1 - store a formatted text file of accounts" << endl

        << "    called \"print.txt\" for printing" << endl

        << "2 - update an account" << endl

        << "3 - add a new account" << endl

        << "4 - delete an account" << endl

        << "5 - end program\n? ";



   int menuChoice;

   cin >> menuChoice; // receive choice from user



   return menuChoice;



} // end function enterChoice



// create formatted text file for printing

void printRecord( fstream &readFromFile )

{

   // create text file

   ofstream outPrintFile( "print.txt", ios::out );



   // exit program if ofstream cannot create file

   if ( !outPrintFile ) {

      cerr << "File could not be created." << endl;

      exit( 1 );



   } // end if



   outPrintFile << left << setw( 10 ) << "Account" << setw( 16 )

       << "Last Name" << setw( 11 ) << "First Name" << right

       << setw( 10 ) << "Balance" << endl;



   // set file-position pointer to beginning of record file

   readFromFile.seekg( 0 );



   // read first record from record file

   ClientData client;

   readFromFile.read( reinterpret_cast< char * >( &client ),

      sizeof( ClientData ) );



   // copy all records from record file into text file

   while ( !readFromFile.eof() ) {



      // write single record to text file

      if ( client.getAccountNumber() != 0 )

         outputLine( outPrintFile, client );



      // read next record from record file

      readFromFile.read( reinterpret_cast< char * >( &client ), 

         sizeof( ClientData ) );



   } // end while



} // end function printRecord



// update balance in record

void updateRecord( fstream &updateFile )

{

   // obtain number of account to update

   int accountNumber = getAccount( "Enter account to update" );



   // move file-position pointer to correct record in file

   updateFile.seekg( 

      ( accountNumber - 1 ) * sizeof( ClientData ) );



   // read first record from file

   ClientData client;

   updateFile.read( reinterpret_cast< char * >( &client ), 

      sizeof( ClientData ) );



   // update record

   if ( client.getAccountNumber() != 0 ) {

      outputLine( cout, client );



      // request user to specify transaction

      cout << "\nEnter charge (+) or payment (-): ";

      double transaction; // charge or payment

      cin >> transaction;



      // update record balance

      double oldBalance = client.getBalance();

      client.setBalance( oldBalance + transaction );

      outputLine( cout, client );



      // move file-position pointer to correct record in file

      updateFile.seekp(

         ( accountNumber - 1 ) * sizeof( ClientData ) );



      // write updated record over old record in file

      updateFile.write( 

         reinterpret_cast< const char * >( &client ), 

         sizeof( ClientData ) );



   } // end if



   // display error if account does not exist

   else

      cerr << "Account #" << accountNumber 

         << " has no information." << endl;



} // end function updateRecord



// create and insert record

void newRecord( fstream &insertInFile )

{

   // obtain number of account to create

   int accountNumber = getAccount( "Enter new account number" );



   // move file-position pointer to correct record in file

   insertInFile.seekg( 

      ( accountNumber - 1 ) * sizeof( ClientData ) );



   // read record from file

   ClientData client;

   insertInFile.read( reinterpret_cast< char * >( &client ), 

      sizeof( ClientData ) );



   // create record, if record does not previously exist

   if ( client.getAccountNumber() == 0 ) {



      char lastName[ 15 ];

      char firstName[ 10 ];

      double balance;



      // user enters last name, first name and balance

      cout << "Enter lastname, firstname, balance\n? ";

      cin >> setw( 15 ) >> lastName;

      cin >> setw( 10 ) >> firstName;

      cin >> balance;



      // use values to populate account values

      client.setLastName( lastName );

      client.setFirstName( firstName );

      client.setBalance( balance );

      client.setAccountNumber( accountNumber );



      // move file-position pointer to correct record in file

      insertInFile.seekp( ( accountNumber - 1 ) * 

         sizeof( ClientData ) );



      // insert record in file

      insertInFile.write( 

         reinterpret_cast< const char * >( &client ), 

         sizeof( ClientData ) );



   } // end if



   // display error if account previously exists

   else

      cerr << "Account #" << accountNumber

           << " already contains information." << endl;



} // end function newRecord



// delete an existing record

void deleteRecord( fstream &deleteFromFile )

{

   // obtain number of account to delete

   int accountNumber = getAccount( "Enter account to delete" );



   // move file-position pointer to correct record in file

   deleteFromFile.seekg( 

      ( accountNumber - 1 ) * sizeof( ClientData ) );



   // read record from file

   ClientData client;

   deleteFromFile.read( reinterpret_cast< char * >( &client ), 

      sizeof( ClientData ) );



   // delete record, if record exists in file

   if ( client.getAccountNumber() != 0 ) {

      ClientData blankClient;



      // move file-position pointer to correct record in file

      deleteFromFile.seekp( ( accountNumber - 1 ) * 

         sizeof( ClientData ) );



      // replace existing record with blank record

      deleteFromFile.write( 

         reinterpret_cast< const char * >( &blankClient ), 

         sizeof( ClientData ) );



      cout << "Account #" << accountNumber << " deleted.\n";



   } // end if



   // display error if record does not exist

   else

      cerr << "Account #" << accountNumber << " is empty.\n";



} // end deleteRecord



// display single record

void outputLine( ostream &output, const ClientData &record )

{

   output << left << setw( 10 ) << record.getAccountNumber()

          << setw( 16 ) << record.getLastName().data()

          << setw( 11 ) << record.getFirstName().data()

          << setw( 10 ) << setprecision( 2 ) << right << fixed 

          << showpoint << record.getBalance() << endl;



} // end function outputLine



// obtain account-number value from user

int getAccount( const char * const prompt )

{

   int accountNumber;



   // obtain account-number value

   do {

      cout << prompt << " (1 - 100): ";

      cin >> accountNumber;



   } while ( accountNumber < 1 || accountNumber > 100 );



   return accountNumber;



} // end function getAccount



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