FileSys::Read( const char *, int, Error * )

Attempt to read len bytes of data from the object referenced by the file handle (returned by the Open() method) to the buffer pointed to by buf. Upon successful completion, Read() returns the number of bytes actually read and placed in the buffer.

Virtual?

Yes

  

Class

FileSys

 

Arguments

const char *buf

pointer to buffer into which to read data
 

int len

length of data to read
 

Error *error

returned error status

Returns

int

number of bytes actually read

Notes

The default implementation of Read() is called every time there is a need to read data from the file referenced by the Open() call.

Your implementation must correctly report any system errors that might occur during I/O.

Example

To use Read() to read a line from a log file:

Copy 
char line[80];
m.Set( msg );
FileSys *f = FileSys::Create( FST_ATEXT );
Error e;

f->Set( "C:\\logfile.txt" );
f->Open( FOM_READ, &e );
f->Read( line, 80, &e );
f->Close( &e );

To reimplement Read() to report errors with Error::Sys(), provide debugging output, and use the FileSysDemo member “fd” to hold the file handle returned from the read() system call:

Copy 
int FileSysDemo::Read( char *buf, int len, Error *e )
{
    int bytes;

    if ( ( bytes = read( fd, buf, len ) ) < 0 )
        e->Sys( "read", Name() );

    if ( DEBUG )
    {
        printf( "debug (Read): %d bytes\n", bytes );
    }

    return( bytes );
}