Lecture 9 • File Processing – Streams – Stream I/O template hierarchy – Read and write sequential text files – Random access files • Binary files
– Reading and writing binary files
TNCG18(C++): Lec 9
1
Introduction • Storage of data – Arrays variables are temporary – Files are permanent • Magnetic disk, optical disk, tapes
• 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
• C++ imposes no structure on file – Concept of "record" must be implemented by programmer TNCG18(C++): Lec 9
2
Files and Streams • When file opened – A stream object associated with it fstream file( "filename", fileOpenMode );
– cin, cout, etc. created when included • Communication between program and file/device badbit failbit …
file
Write file position pointer Read file position pointer 0
1
2
3
4
5
6
7
8
9
... ...
TNCG18(C++): Lec 9
n-1 end-of-file marker
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 for files • ifstream (char input) • ofstream (char output) • fstream (char I/O)
TNCG18(C++): Lec 9
4
I/O Template Hierarchy • typedefs for specializations that allow char I/O • istream specialization of basic_istream (char input) • ostream specialization of basic_ostream (char output) • cin is an instance of istream • cout is an instance of ostream basic_ios
basic_istream
basic_ifstream
basic_ostream
basic_iostream
basic_ofstream
basic_fstream
TNCG18(C++): Lec 9
5
An Example // display single record void outputLine( ostream &output, const ClientData &record ) { output > score ) { moviesData
