File Processing

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File Processing Outline 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9 14.10 14.11 14.12

Introduction The Data Hierarchy Files and Streams Creating a Sequential-Access File Reading Data from a Sequential-Access File Updating Sequential-Access Files Random-Access Files Creating a Random-Access File Writing Data Randomly to a Random-Access File Reading Data Sequentially from a Random-Access File Example: A Transaction-Processing Program Input/Output of Objects

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14.1 Introduction • Storage of data – Arrays, variables are temporary – Files are permanent • Magnetic disk, optical disk, tapes

• In this chapter – Create, update, process files – Sequential and random access – Formatted and raw processing

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14.2 The Data Hierarchy • From smallest to largest – Bit (binary digit) • • • •

1 or 0 Everything in computer ultimately represented as bits Cumbersome for humans to use Character set – Digits, letters, symbols used to represent data – Every character represented by 1's and 0's

– Byte: 8 bits • Can store a character (char) • Also Unicode for large character sets (wchar_t)

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14.2 The Data Hierarchy • From smallest to largest (continued) – Field: group of characters with some meaning • Your name

– Record: group of related fields • struct or class in C++ • In payroll system, could be name, SS#, address, wage • Each field associated with same employee • Record key: field used to uniquely identify record

– File: group of related records • Payroll for entire company • Sequential file: records stored by key

– Database: group of related files • Payroll, accounts-receivable, inventory… © 2003 Prentice Hall, Inc. All rights reserved.

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14.2 The Data Hierarchy

Sally Tom Judy Iris Randy

Judy

Black Blue Green Orange Red

Green

Judy

Field

01001010 Byte (ASCII character J) 1 Bit

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File

Record

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14.3 Files and Streams • C++ views file as sequence of bytes – Ends with end-of-file marker 0

1

2

3

4

5

6

7

8

9

... ...

n-1 end-of-file marker

• When file opened – Object created, stream associated with it – cin, cout, etc. created when included • Communication between program and file/device

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14.3 Files and Streams • To perform file processing – Include and – Class templates • basic_ifstream (input) • basic_ofstream (output) • basic_fstream (I/O)

– typedefs for specializations that allow char I/O • ifstream (char input) • ofstream (char output) • fstream (char I/O)

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14.3 Files and Streams • Opening files – Create objects from template – Derive from stream classes • Can use stream methods from Ch. 12 • put, get, peek, etc. basic_ios

basic_istream

basic_ifstream

basic_ostream

basic_iostream

basic_fstream

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basic_ofstream

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14.4 Creating a Sequential-Access File • C++ imposes no structure on file – Concept of "record" must be implemented by programmer

• To open file, create objects – Creates "line of communication" from object to file – Classes • ifstream (input only) • ofstream (output only) • fstream (I/O)

– Constructors take file name and file-open mode ofstream outClientFile( "filename", fileOpenMode );

– To attach a file later Ofstream outClientFile; outClientFile.open( "filename", fileOpenMode);

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14.4 Creating a Sequential-Access File • File-open modes Mode

Description

ios::app

Write all output to the end of the file.

ios::ate

Open a file for output and move to the end of the file (normally used to append data to a file). Data can be written anywhere in the file. Open a file for input. Open a file for output. Discard the file’s contents if it exists (this is also the default action for ios::out)

ios::in ios::out ios::trunc ios::binary

Open a file for binary (i.e., non-text) input or output.

– ofstream opened for output by default • ofstream outClientFile( "clients.dat", ios::out ); • ofstream outClientFile( "clients.dat");

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14.4 Creating a Sequential-Access File • Operations – Overloaded operator! • !outClientFile • Returns nonzero (true) if badbit or failbit set – Opened non-existent file for reading, wrong permissions

– Overloaded operator void* • Converts stream object to pointer • 0 when when failbit or badbit set, otherwise nonzero – failbit set when EOF found • while ( cin >> myVariable ) – Implicitly converts cin to pointer – Loops until EOF

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14.4 Creating a Sequential-Access File • Operations – Writing to file (just like cout) • outClientFile << myVariable

– Closing file • outClientFile.close() • Automatically closed when destructor called

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// Fig. 14.4: fig14_04.cpp // Create a sequential file. #include using using using using using

Outline fig14_04.cpp (1 of 2)

std::cout; std::cin; std::ios; std::cerr; std::endl;

#include using std::ofstream; #include

Notice the the header files required for file I/O. // exit prototype

int main() { // ofstream constructor opens file ofstream outClientFile( "clients.dat", ios::out ); // exit program if unable to create file if ( !outClientFile ) { // overloaded ! operator cerr << "File could not be opened" << endl; exit( 1 );

ofstream object created and used to open file "clients.dat". If the file does not exist, it is created. ! operator used to test if the file opened properly.

} // end if

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14 cout << "Enter the account, name, and balance." << endl << "Enter end-of-file to end input.\n? "; int account; char name[ 30 ]; double balance;

cin is implicitly converted to a pointer. When EOF is encountered, it returns 0 and the loop stops.

Outline fig14_04.cpp (2 of 2)

// read account, name and balance from cin, then place in file while ( cin >> account >> name >> balance ) { outClientFile << account << ' ' << name << ' ' << balance << endl; cout << "? "; } // end while return 0; } // end main

Write data to file like a regular stream.

// ofstream destructor closes file

File closed when destructor called for object. Can be explicitly closed with close().

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Enter Enter ? 100 ? 200 ? 300 ? 400 ? 500 ? ^Z

the account, name, and balance. end-of-file to end input. Jones 24.98 Doe 345.67 White 0.00 Stone -42.16 Rich 224.62

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Outline fig14_04.cpp output (1 of 1)

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14.5 Reading Data from a SequentialAccess File • Reading files – ifstream inClientFile( "filename", ios::in );

– Overloaded ! • !inClientFile tests if file was opened properly

– operator void* converts to pointer • while (inClientFile >> myVariable) • Stops when EOF found (gets value 0)

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// Fig. 14.7: fig14_07.cpp // Reading and printing a sequential file. #include using using using using using using using using using

std::cout; std::cin; std::ios; std::cerr; std::endl; std::left; std::right; std::fixed; std::showpoint;

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Outline fig14_07.cpp (1 of 3)

#include using std::ifstream; #include using std::setw; using std::setprecision; #include // exit prototype void outputLine( int, const char * const, double );

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int main() { // ifstream constructor opens the file ifstream inClientFile( "clients.dat", ios::in ); // exit program if ifstream could not open file if ( !inClientFile ) { cerr << "File could not be opened" << endl; exit( 1 );

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Outline Open and test file for input. fig14_07.cpp (2 of 3)

} // end if int account; char name[ 30 ]; double balance; cout << left << setw( 10 ) << "Account" << setw( 13 ) Read from<
found. // display each record in file while ( inClientFile >> account >> name >> balance ) outputLine( account, name, balance ); return 0; // ifstream destructor closes the file } // end main

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19 // display single record from file void outputLine( int account, const char * const name, double balance ) { cout << left << setw( 10 ) << account << setw( 13 ) << name << setw( 7 ) << setprecision( 2 ) << right << balance << endl;

Outline fig14_07.cpp (3 of 3) fig14_07.cpp output (1 of 1)

} // end function outputLine

Account 100 200 300 400 500

Name Jones Doe White Stone Rich

Balance 24.98 345.67 0.00 -42.16 224.62

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14.5 Reading Data from a SequentialAccess File • File position pointers – Number of next byte to read/write – Functions to reposition pointer • seekg (seek get for istream class) • seekp (seek put for ostream class) • Classes have "get" and "put" pointers

– seekg and seekp take offset and direction • Offset: number of bytes relative to direction • Direction (ios::beg default) – ios::beg - relative to beginning of stream – ios::cur - relative to current position – ios::end - relative to end

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14.5 Reading Data from a SequentialAccess File • Examples – fileObject.seekg(0) • Goes to front of file (location 0) because ios::beg is default

– fileObject.seekg(n) • Goes to nth byte from beginning

– fileObject.seekg(n, ios::cur) • Goes n bytes forward

– fileObject.seekg(y, ios::end) • Goes y bytes back from end

– fileObject.seekg(0, ios::cur) • Goes to last byte

– seekp similar © 2003 Prentice Hall, Inc. All rights reserved.

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14.5 Reading Data from a SequentialAccess File • To find pointer location – tellg and tellp – location = fileObject.tellg()

• Upcoming example – Credit manager program – List accounts with zero balance, credit, and debit

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// Fig. 14.8: fig14_08.cpp // Credit-inquiry program. #include using using using using using using using using using

std::cout; std::cin; std::ios; std::cerr; std::endl; std::fixed; std::showpoint; std::left; std::right;

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Outline fig14_08.cpp (1 of 6)

#include using std::ifstream; #include using std::setw; using std::setprecision; #include

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enum RequestType { ZERO_BALANCE = 1, CREDIT_BALANCE, DEBIT_BALANCE, END }; int getRequest(); bool shouldDisplay( int, double ); void outputLine( int, const char * const, double );

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Outline fig14_08.cpp (2 of 6)

int main() { // ifstream constructor opens the file ifstream inClientFile( "clients.dat", ios::in ); // exit program if ifstream could not open file if ( !inClientFile ) { cerr << "File could not be opened" << endl; exit( 1 ); } // end if int request; int account; char name[ 30 ]; double balance; // get user's request (e.g., zero, credit or debit balance) request = getRequest();

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// process user's request while ( request != END ) { switch ( request ) { case ZERO_BALANCE: cout << "\nAccounts with zero balances:\n"; break;

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Outline fig14_08.cpp (3 of 6)

case CREDIT_BALANCE: cout << "\nAccounts with credit balances:\n"; break; case DEBIT_BALANCE: cout << "\nAccounts with debit balances:\n"; break; } // end switch

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// read account, name and balance from file inClientFile >> account >> name >> balance; // display file contents (until eof) while ( !inClientFile.eof() ) {

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Outline fig14_08.cpp (4 of 6)

// display record if ( shouldDisplay( request, balance ) ) outputLine( account, name, balance ); // read account, name and balance from file inClientFile >> account >> name >> balance; } // end inner while

Use clear to reset eof. Use seekg to set file position pointer to beginning of file.

inClientFile.clear(); // reset eof for next input inClientFile.seekg( 0 ); // move to beginning of file request = getRequest(); // get additional request from user } // end outer while cout << "End of run." << endl; return 0; // ifstream destructor closes the file } // end main

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27 // obtain request from user int getRequest() { int request;

Outline fig14_08.cpp (5 of 6)

// display request options cout << "\nEnter request" << endl << " 1 - List accounts with zero balances" << endl << " 2 - List accounts with credit balances" << endl << " 3 - List accounts with debit balances" << endl << " 4 - End of run" << fixed << showpoint; // input user request do { cout << "\n? "; cin >> request; } while ( request < ZERO_BALANCE && request > END ); return request; } // end function getRequest

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// determine whether to display given record bool shouldDisplay( int type, double balance ) { // determine whether to display credit balances if ( type == CREDIT_BALANCE && balance < 0 ) return true;

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Outline fig14_08.cpp (6 of 6)

// determine whether to display debit balances if ( type == DEBIT_BALANCE && balance > 0 ) return true; // determine whether to display zero balances if ( type == ZERO_BALANCE && balance == 0 ) return true; return false; } // end function shouldDisplay // display single record from file void outputLine( int account, const char * const name, double balance ) { cout << left << setw( 10 ) << account << setw( 13 ) << name << setw( 7 ) << setprecision( 2 ) << right << balance << endl; } // end function outputLine

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Enter request 1 - List accounts with zero balances 2 - List accounts with credit balances 3 - List accounts with debit balances 4 - End of run ? 1

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Outline fig14_08.cpp output (1 of 2)

Accounts with zero balances: 300 White 0.00 Enter request 1 - List accounts with zero balances 2 - List accounts with credit balances 3 - List accounts with debit balances 4 - End of run ? 2 Accounts with credit balances: 400 Stone -42.16

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Enter request 1 - List accounts with zero balances 2 - List accounts with credit balances 3 - List accounts with debit balances 4 - End of run ? 3

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Outline fig14_08.cpp output (2 of 2)

Accounts with debit balances: 100 Jones 24.98 200 Doe 345.67 500 Rich 224.62 Enter request 1 - List accounts with zero balances 2 - List accounts with credit balances 3 - List accounts with debit balances 4 - End of run ? 4 End of run.

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14.6 Updating Sequential-Access Files • Updating sequential files – Risk overwriting other data – Example: change name "White" to "Worthington" • Old data 300 White 0.00 400 Jones 32.87

• Insert new data 300 Worthington 0.00 300 White 0.00 400 Jones 32.87

Data gets overwritten 300 Worthington 0.00ones 32.87

– Formatted text different from internal representation – Problem can be avoided, but awkward © 2003 Prentice Hall, Inc. All rights reserved.

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14.7 Random-Access Files • Instant access – Want to locate record quickly • Airline reservations, ATMs

– Sequential files must search through each one

• Random-access files are solution – Instant access – Insert record without destroying other data – Update/delete items without changing other data

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14.7 Random-Access Files • C++ imposes no structure on files – Programmer must create random-access files – Simplest way: fixed-length records • Calculate position in file from record size and key 0

100

200

300

400

500

}

byte offsets

}

}

}

}

}

}

100

100

100

100

100

100

bytes

bytes

bytes

bytes

bytes

bytes

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14.8 Creating a Random-Access File • "1234567" (char *) vs 1234567 (int) – char * takes 8 bytes (1 for each character + null) – int takes fixed number of bytes (perhaps 4) • 123 same size in bytes as 1234567

• << operator and write() – outFile << number • Outputs number (int) as a char * • Variable number of bytes

– outFile.write( const char *, size ); • Outputs raw bytes • Takes pointer to memory location, number of bytes to write – Copies data directly from memory into file – Does not convert to char * © 2003 Prentice Hall, Inc. All rights reserved.

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14.8 Creating a Random-Access File • Example outFile.write( reinterpret_cast(&number), sizeof( number ) );

– &number is an int * • Convert to const char * with reinterpret_cast

– sizeof(number) • Size of number (an int) in bytes

– read function similar (more later) – Must use write/read between compatible machines • Only when using raw, unformatted data

– Use ios::binary for raw writes/reads

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14.8 Creating a Random-Access File • Usually write entire struct or object to file • Problem statement – Credit processing program – Store at most 100 fixed-length records – Record • Account number (key) • First and last name • Balance

– Account operations • Update, create new, delete, list all accounts in a file

• Next: program to create blank 100-record file © 2003 Prentice Hall, Inc. All rights reserved.

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// Fig. 14.10: clientData.h // Class ClientData definition used in Fig. 14.12–Fig. 14.15. #ifndef CLIENTDATA_H #define CLIENTDATA_H #include using std::string;

Class ClientData stores the information for each person. 100 blank ClientData objects will be written to a file.

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Outline clientData.h (1 of 2)

class ClientData { public: // default ClientData constructor ClientData( int = 0, string = "", string = "", double = 0.0 ); // accessor functions for accountNumber void setAccountNumber( int ); int getAccountNumber() const; // accessor functions for lastName void setLastName( string ); string getLastName() const;

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// accessor functions for firstName void setFirstName( string ); string getFirstName() const;

Outline clientData.h (2 of 2)

// accessor functions for balance void setBalance( double ); double getBalance() const; private: int accountNumber; char lastName[ 15 ]; char firstName[ 10 ]; double balance;

Put limits on the size of the first and last name. accountNumber (an int) and balance (double) are already of a fixed size.

}; // end class ClientData #endif

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// Fig. 14.11: ClientData.cpp // Class ClientData stores customer's credit information. #include using std::string;

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Outline ClientData.cpp (1 of 4)

#include #include "clientData.h" // default ClientData constructor ClientData::ClientData( int accountNumberValue, string lastNameValue, string firstNameValue, double balanceValue ) { setAccountNumber( accountNumberValue ); setLastName( lastNameValue ); setFirstName( firstNameValue ); setBalance( balanceValue ); } // end ClientData constructor // get account-number value int ClientData::getAccountNumber() const { return accountNumber; } // end function getAccountNumber

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40 // set account-number value void ClientData::setAccountNumber( int accountNumberValue ) { accountNumber = accountNumberValue;

Outline ClientData.cpp (2 of 4)

} // end function setAccountNumber // get last-name value string ClientData::getLastName() const { return lastName; } // end function getLastName // set last-name value void ClientData::setLastName( string lastNameString ) { // copy at most 15 characters from string to lastName const char *lastNameValue = lastNameString.data(); int length = strlen( lastNameValue ); length = ( length < 15 ? length : 14 ); strncpy( lastName, lastNameValue, length ); // append null character to lastName lastName[ length ] = '\0';

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41 } // end function setLastName // get first-name value string ClientData::getFirstName() const { return firstName;

Outline ClientData.cpp (3 of 4)

} // end function getFirstName // set first-name value void ClientData::setFirstName( string firstNameString ) { // copy at most 10 characters from string to firstName const char *firstNameValue = firstNameString.data(); int length = strlen( firstNameValue ); length = ( length < 10 ? length : 9 ); strncpy( firstName, firstNameValue, length ); // append new-line character to firstName firstName[ length ] = '\0'; } // end function setFirstName

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// get balance value double ClientData::getBalance() const { return balance; } // end function getBalance

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Outline ClientData.cpp (4 of 4)

// set balance value void ClientData::setBalance( double balanceValue ) { balance = balanceValue; } // end function setBalance

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// Fig. 14.12: fig14_12.cpp // Creating a randomly accessed file. #include

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Outline fig14_12.cpp (1 of 2)

using std::cerr; using std::endl; using std::ios; #include using std::ofstream; #include #include "clientData.h"

// ClientData class definition

int main() { ofstream outCredit( "credit.dat", ios::binary );

Open a file for raw writing using an ofstream object and ios::binary.

// exit program if ofstream could not open file if ( !outCredit ) { cerr << "File could not be opened." << endl; exit( 1 ); } // end if

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44 // create ClientData with no information ClientData blankClient;

Outline Create a blank object. Use write to output the raw data fig14_12.cpp to a file (passing a pointer to (2 of 2) the object and its size).

// output 100 blank records to file for ( int i = 0; i < 100; i++ ) outCredit.write( reinterpret_cast< const char * >( &blankClient ), sizeof( ClientData ) ); return 0; } // end main

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14.9 Writing Data Randomly to a RandomAccess File • Use seekp to write to exact location in file – Where does the first record begin? • Byte 0

– The second record? • Byte 0 + sizeof(object)

– Any record? • (Recordnum - 1) * sizeof(object)

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// Fig. 14.13: fig14_13.cpp // Writing to a random access file. #include using using using using using

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Outline fig14_13.cpp (1 of 4)

std::cerr; std::endl; std::cout; std::cin; std::ios;

#include using std::setw; #include using std::ofstream; #include #include "clientData.h"

// ClientData class definition

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int main() { int accountNumber; char lastName[ 15 ]; char firstName[ 10 ]; double balance;

Outline fig14_13.cpp Open file for raw (binary) (2 of 4) writing.

ofstream outCredit( "credit.dat", ios::binary ); // exit program if ofstream cannot open file if ( !outCredit ) { cerr << "File could not be opened." << endl; exit( 1 ); } // end if cout << "Enter account number " << "(1 to 100, 0 to end input)\n? ";

Get account number, put into number object. It has not yet been written to file.

// require user to specify account ClientData client; cin >> accountNumber; client.setAccountNumber( accountNumber );

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// user enters information, which is copied into file while ( client.getAccountNumber() > 0 && client.getAccountNumber() <= 100 ) { // user enters last name, first name and balance cout << "Enter lastname, firstname, balance\n? "; cin >> setw( 15 ) >> lastName; cin >> setw( 10 ) >> firstName; cin >> balance;

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Outline fig14_13.cpp (3 of 4)

// set record lastName, firstName and balance values Position outCredit to the client.setLastName( lastName ); proper location in the file client.setFirstName( firstName ); (based on the account client.setBalance( balance );

number). // seek position in file of user-specified record outCredit.seekp( ( client.getAccountNumber() - 1 ) * Write ClientData sizeof( ClientData ) );

object to file at specified position.

// write user-specified information in file outCredit.write( reinterpret_cast< const char * >( &client ), sizeof( ClientData ) );

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// enable user to specify another account number cout << "Enter account number\n? "; cin >> accountNumber; client.setAccountNumber( accountNumber ); } // end while

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Outline fig14_13.cpp (4 of 4)

return 0; } // end main

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Enter account number (1 to ? 37 Enter lastname, firstname, ? Barker Doug 0.00 Enter account number ? 29 Enter lastname, firstname, ? Brown Nancy -24.54 Enter account number ? 96 Enter lastname, firstname, ? Stone Sam 34.98 Enter account number ? 88 Enter lastname, firstname, ? Smith Dave 258.34 Enter account number ? 33 Enter lastname, firstname, ? Dunn Stacey 314.33 Enter account number ? 0

100, 0 to end input)

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Outline

balance

Notice that accounts can be created in any order.

fig14_13.cpp output (1 of 1)

balance

balance

balance

balance

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14.10 Reading Data Sequentially from a Random-Access File • read - similar to write – Reads raw bytes from file into memory – inFile.read( reinterpret_cast( &number ), sizeof( int ) );

• &number: location to store data • sizeof(int): how many bytes to read

– Do not use inFile >> number with raw bytes • >> expects char *

• Upcoming program – Output data from a random-access file – Go through each record sequentially • If no data (accountNumber == 0) then skip

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// Fig. 14.14: fig14_14.cpp // Reading a random access file. #include using using using using using using using using

std::cout; std::endl; std::ios; std::cerr; std::left; std::right; std::fixed; std::showpoint;

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Outline fig14_14.cpp (1 of 3)

#include using std::setprecision; using std::setw; #include using std::ifstream; using std::ostream; #include // exit protoyype #include "clientData.h" // ClientData class definition

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void outputLine( ostream&, const ClientData & ); int main() { ifstream inCredit( "credit.dat", ios::in );

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Outline fig14_14.cpp (2 of 3)

// exit program if ifstream cannot open file if ( !inCredit ) { cerr << "File could not be opened." << endl; exit( 1 ); } // end if

Read sizeof(ClientData) bytes and put empty

cout << left << setw( 10 ) << "Account" << setw( 16 ) into object client. This may be an << "Last Name" << setw( 11 ) << "First Name" << left record. << setw( 10 ) << right << "Balance" << endl; ClientData client; // create record // read first record from file inCredit.read( reinterpret_cast< char * >( &client ), sizeof( ClientData ) );

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// read all records from file while ( inCredit && !inCredit.eof() ) {

Outline

// display record if ( client.getAccountNumber() != 0 ) outputLine( cout, client );

Loop exits if there is an error fig14_14.cpp reading (inCredit == 0) (3 of 3) or EOF is found (inCredit.eof() == 1)

// read next from file inCredit.read( reinterpret_cast< char * >( &client ), sizeof( ClientData ) ); } // end while return 0; } // end main

Output non-empty accounts. Note that outputLine takes an ostream argument. We could easily output to another file (opened with an ofstream object, which derives from ostream).

// 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 outputLine

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Account 29 33 37 88 96

Last Name Brown Dunn Barker Smith Stone

First Name Nancy Stacey Doug Dave Sam

Balance -24.54 314.33 0.00 258.34 34.98

55

Outline fig14_14.cpp output (1 of 1)

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56

14.11 Example: A Transaction-Processing Program • Instant access for bank accounts – Use random access file (data in client.dat)

• Give user menu – Option 1: store accounts to print.txt Account 29 33 37 88 96

Last Name Brown Dunn Barker Smith Stone

First Name Nancy Stacey Doug Dave Sam

Balance -24.54 314.33 0.00 258.34 34.98

– Option 2: update record Enter account to update (1 - 100): 37 37 Barker Doug Enter charge (+) or payment (-): +87.99 37 Barker Doug

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0.00

87.99

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14.11 Example: A Transaction-Processing Program • Menu options (continued) – Option 3: add new record Enter new account number (1 - 100): 22 Enter lastname, firstname, balance ? Johnston Sarah 247.45

– Option 4: delete record Enter account to delete (1 - 100): 29 Account #29 deleted.

• To open file for reading and writing – Use fstream object – "Or" file-open modes together fstream inOutCredit( "credit.dat", ios::in | ios::out );

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// 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 using using using using using using using using using

58

Outline fig14_15.cpp (1 of 14)

std::cout; std::cerr; std::cin; std::endl; std::ios; std::left; std::right; std::fixed; std::showpoint;

#include using std::ofstream; using std::ostream; using std::fstream; #include using std::setw; using std::setprecision; #include #include "clientData.h"

// exit prototype // ClientData class definition

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30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

59 int enterChoice(); void printRecord( fstream& ); void updateRecord( fstream& ); void newRecord( fstream& ); void deleteRecord( fstream& ); void outputLine( ostream&, const ClientData & ); int getAccount( const char * const );

Outline fig14_15.cpp (2 of 14)

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

Open file for reading and

int main() writing (fstream object { // open file for reading and writing needed). 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

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int choice; // enable user to specify action while ( ( choice = enterChoice() ) != END ) { switch ( choice ) {

60

Outline fig14_15.cpp (3 of 14)

// 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;

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61

int choice;

Outline

// enable user to specify action while ( ( choice = enterChoice() ) != END ) { switch ( choice ) {

Displays menu and returns user's choice.

fig14_15.cpp (4 of 14)

// 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;

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// display error if user does not select valid choice default: cerr << "Incorrect choice" << endl; break; } // end switch

62

Outline fig14_15.cpp (5 of 14)

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? ";

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63 int menuChoice; cin >> menuChoice; // receive choice from user return menuChoice;

Outline fig14_15.cpp (6 of 14)

} // end function enterChoice // create formatted text file for printing Output to print.txt. First, void printRecord( fstream &readFromFile ) print the header for the table. { // 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;

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131 // set file-position pointer to beginning of record file 132 readFromFile.seekg( 0 ); 133 134 // read first record from record file Go to front of file, read fig14_15.cpp 135 ClientData client; account data,(7and print record of 14) 136 readFromFile.read( reinterpret_cast< char * >( &client ), if not empty. 137 sizeof( ClientData ) ); 138 Note that outputLine 139 // copy all records from record file into text file takes an ostream object 140 while ( !readFromFile.eof() ) { (base of ofstream). It can 141 easily print to a file (as in this 142 // write single record to text file 143 if ( client.getAccountNumber() != 0 ) case) or cout. 144 outputLine( outPrintFile, client ); 145 146 // read next record from record file 147 readFromFile.read( reinterpret_cast< char * >( &client ), 148 sizeof( ClientData ) ); 149 150 } // end while 151 152 } // end function printRecord 153

Outline

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64

154 // update balance in record 155 void updateRecord( fstream &updateFile ) 156 { 157 // obtain number of account to update 158 int accountNumber = getAccount( "Enter account to update" ); 159 160 // move file-position pointer to correct record in file This is fstream (I/O) 161 updateFile.seekg( 162 ( accountNumber - 1 ) * sizeof( ClientData ) ); because we must read the old 163 balance, update it, and write 164 // read first record from file the new balance. 165 ClientData client; 166 updateFile.read( reinterpret_cast< char * >( &client ), 167 sizeof( ClientData ) ); 168 169 // update record 170 if ( client.getAccountNumber() != 0 ) { 171 outputLine( cout, client ); 172 173 // request user to specify transaction 174 cout << "\nEnter charge (+) or payment (-): "; 175 double transaction; // charge or payment 176 cin >> transaction; 177 178 // update record balance 179 double oldBalance = client.getBalance(); 180 client.setBalance( oldBalance + transaction ); 181 outputLine( cout, client ); 182

65

Outline fig14_15.cpp (8 of 14)

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66

// move file-position pointer to correct record in file updateFile.seekp( ( accountNumber - 1 ) * sizeof( ClientData ) );

Outline fig14_15.cpp (9 of 14)

// 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 This is fstream because cerr << "Account #" << accountNumber read to see if a non-empty << " has no information." << endl; } // end function updateRecord

we

record already exists. If not, we write a new record.

// 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 ) );

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67 // read record from file ClientData client; insertInFile.read( reinterpret_cast< char * >( &client ), sizeof( ClientData ) );

Outline fig14_15.cpp (10 of 14)

// 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 );

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235 // move file-position pointer to correct record in file 236 insertInFile.seekp( ( accountNumber - 1 ) * 237 sizeof( ClientData ) ); 238 239 // insert record in file 240 insertInFile.write( 241 reinterpret_cast< const char * >( &client ), 242 sizeof( ClientData ) ); 243 244 } // end if 245 246 // display error if account previously exists 247 else 248 cerr << "Account #" << accountNumber 249 << " already contains information." << endl; 250 251 } // end function newRecord 252

68

Outline fig14_15.cpp (11 of 14)

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253 // delete an existing record 254 void deleteRecord( fstream &deleteFromFile ) 255 { 256 // obtain number of account to delete fig14_15.cpp 257 int accountNumber = getAccount( "Enter account to delete" ); (12 of 14) 258 259 // move file-position pointer to correct record in file 260 deleteFromFile.seekg( 261 ( accountNumber - 1 ) * sizeof( ClientData ) ); fstream because we read to 262 check if the account exits. If 263 // read record from file it does, we write blank data 264 ClientData client; (erase it). 265 deleteFromFile.read( reinterpret_cast< char * >( &client ), If it does not exist, there is no need to delete it. 266 sizeof( ClientData ) ); 267 268 // delete record, if record exists in file 269 if ( client.getAccountNumber() != 0 ) { 270 ClientData blankClient; 271 272 // move file-position pointer to correct record in file 273 deleteFromFile.seekp( ( accountNumber - 1 ) * 274 sizeof( ClientData ) ); 275

Outline

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// replace existing record with blank record deleteFromFile.write( reinterpret_cast< const char * >( &blankClient ), sizeof( ClientData ) ); cout << "Account #" << accountNumber << " deleted.\n";

70

Outline fig14_15.cpp (13 of 14)

} // end if // display error if record does not exist else is very cerr << "Account #" << accountNumber outputLine << " is empty.\n"; } // end deleteRecord

flexible, and can output to any ostream object (such as a file or cout).

// 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

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// 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;

71

Outline fig14_15.cpp (14 of 14)

} while ( accountNumber < 1 || accountNumber > 100 ); return accountNumber; } // end function getAccount

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14.12 Input/Output of Objects • I/O of objects – Chapter 8 (overloaded >>) – Only object's data transmitted • Member functions available internally

– When objects stored in file, lose type info (class, etc.) • Program must know type of object when reading

– One solution • When writing, output object type code before real object • When reading, read type code – Call proper overloaded function (switch)

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