Thread: Converting a C structure into a C++ class

Experts, I have been racking my brain over this one for the past two days. It should be simple but for the life of me I cannot figure it out. I want to convert the following structure into a class:

Code:

#define SIOC_SERIAL    _IOR('S', 254, struct scsi_serial)

struct scsi_serial{
    ubit8  device_type;         // SCSI Device Type.
    ubit8  page_code;          // SCSI Page Code.
    ubit8  reserved;             // SCSI Reserved.
    ubit8  page_length;       // SCSI Page Length.
    ubit8  serial[252];          // SCSI Serial Number.
};

The above mentioned structure is from the HPUX 11i scsi.h and scsi_ctl.h files.

The closest that I have been able to come is as follows:

Code:

/**************************************************
 **
 ** Filename: cdskinfo2.h
 **
 ** Purpose:
 **
**************************************************/

#ifndef _CDSKINFO2_H_
#define _CDSKINFO2_H_
#include <string>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>

#define SIOC_SERIAL    _IOR('S', 254, struct scsi_serial)

struct scsi_serial{
    ubit8  device_type;        // SCSI Device Type.
    ubit8  page_code;          // SCSI Page Code.
    ubit8  reserved;           // SCSI Reserved.
    ubit8  page_length;        // SCSI Page Length.
    ubit8  serial[252];        // SCSI Serial Number.
};

class CdskInfo{
 public:
    /* Data Members */
    char device_name[256];        // SCSI Device Name.
    struct scsi_serial sn;

    // Constructor
    CdskInfo( char *s );

    /* Public Methods */
    void print_device_name();
    void dump();
    int open_device();
};
#endif

Code:

/**************************************************
 **
 ** Filename: cdskinfo2.c
 **
 ** Purpose:
 **
 **************************************************/
#include "cdskinfo2.h"

CdskInfo::CdskInfo( char *s ){
    int fd, ret;
    strcpy( device_name, s );
    open_device();
}

void CdskInfo::print_device_name(){
    printf ( "SCSI_DEVICE_NAME=%s\n", device_name );
}

void CdskInfo::dump(){
    printf ( "SCSI_DEVICE_NAME=%s\n", device_name );
    printf ( "SCSI_SERIAL_NUMBER=%s\n", sn.serial );
}

int CdskInfo::open_device ( ){
    int fd, ret;
    if ( ( fd = open( device_name, O_RDONLY | O_NDELAY ) ) <= 0 ){
        perror( "Open Error" );
        return ( -1 );
    }

    if ( ( ret = ioctl( fd, SIOC_SERIAL, &sn ) ) != 0 ){
        perror( "SIOC_SERIAL Error" );
        return ( -1 );
    }
    return ( ret );
}

Code:

/**************************************************
 **
 ** Filename: cdskinfo_main.cc
 **
 ** Purpose:
 **
**************************************************/

#include <iostream.h>
#include <cstdlib>
#include "cdskinfo2.h"

int main ( int argc, char *argv[] ) {

    CdskInfo sserial( argv[1] );

    sserial.print_device_name();
    sserial.dump();

  exit( 0 );
}

The above source compiles and runs fine but it is not quite what I am trying to accomplish. My main desire is to eliminate the need to physically define the scsi_serial structure all to gether and just have a "pure" class based on this structure. One of the biggest hurdles I have had in this conversion is with the ioctl statement.

Can anyone help me in solving this problem.

Thanks in advance,

DeadPoet

Consider the following:

Code:

#include <iostream>
#include <cstring>
using namespace std;

struct Test
{
    char c;
    int i;
    char str[20];
    float f;
};//Test

void print_Test(const Test *t)
{
    cout << "c = " << t->c << endl
         << "i = " << t->i << endl
         << "f = " << t->f << endl
         << "str = " << t->str << endl;
}//print_Test

class CTest : public Test
{
public:
    CTest()
    {
        c = 'X';
        i = 69;
        f = 2.5;
        strcpy(str, "Hello");
    }//constructor

    void print() 
    {
        print_Test(this);
    }//print
};//CTest

int main()
{
    CTest t;
    t.print();
    print_Test(&t);
    
    return 0;
}//main

gg

Specifically, what is the difficulty with ioctl()?

Kuphryn

Kuphryn and All Others,

Consider the following code changes from the original posted source--All modifications are noted by CHANGE_MADE_HERE.

Code:

/*************************************************
 **
 ** Filename: cdskinfo3.h
 **
 ** Purpose:
 **
 *************************************************/
#ifndef _CDSKINFO2_H_
#define _CDSKINFO2_H_
#include <string>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/scsi.h>

/* CHANGE_MADE_HERE */
#define SIOC_SERIAL    _IOR('S', 254, class CdskInfo)

/* CHANGE_MADE_HERE */
/* Structure commented and now defined as Data Members */
/*
struct scsi_serial{
    ubit8  device_type;        // SCSI Device Type.
    ubit8  page_code;          // SCSI Page Code.
    ubit8  reserved;           // SCSI Reserved.
    ubit8  page_length;        // SCSI Page Length.
    ubit8  serial[252];        // SCSI Serial Number.
};
*/

class CdskInfo{
 public:
    /* Data Members */

    char device_name[256];        // SCSI Device Name.
    
        /* CHANGE_MADE_HERE */
    //    struct scsi_serial sn;
    
    /* CHANGE_MADE_HERE */
    ubit8  device_type;        // SCSI Device Type.
    ubit8  page_code;          // SCSI Page Code.
    ubit8  reserved;           // SCSI Reserved.
    ubit8  page_length;        // SCSI Page Length.
    ubit8  serial[252];        // SCSI Serial Number.

    // Constructor

    CdskInfo( char *s );

    /* Public Methods */
    void print_device_name();
    void dump();
    int open_device();
};

#endif

Code:

/*************************************************
 **
 ** Filename: cdskinfo3.c
 **
 ** Purpose:
 **
 *************************************************/
#include "cdskinfo2.h"

CdskInfo::CdskInfo( char *s ){
    int fd, ret;
    strcpy( device_name, s );
    open_device();
}

void CdskInfo::print_device_name(){
    printf ( "SCSI_DEVICE_NAME=%s\n", device_name );
}

void CdskInfo::dump(){
    printf ( "SCSI_DEVICE_NAME=%s\n", device_name );   
    printf ( "SCSI_SERIAL_NUMBER=%s\n", serial );    
}

int CdskInfo::open_device ( ){    
    int fd, ret;    
    if ( ( fd = open( device_name, O_RDONLY | O_NDELAY ) ) <= 0 ){	
	perror( "Open Error" );	
	return ( -1 );	
    }
/* CHANGE_MADE_HERE */
/* ioctl Now does not open the device */
    if ( ( ret = ioctl( fd, CSIOC_SERIAL, &(*this) ) ) != 0 ){
	perror( "SIOC_SERIAL ERROR" );
	return ( -1 );
    }
    return ( ret );
}

Code:

/*************************************************
 **
 ** Filename: cdskinfo_main.cc
 **
 ** Purpose:
 **
 *************************************************/

#include <iostream.h>
#include <cstdlib> // for exit()
#include "cdskinfo2.h"

int main ( int argc, char *argv[] ) {

    CdskInfo sserial( argv[1] );
    
    cout << "*****DEBUG*****"  << endl;
    sserial.print_device_name();
    sserial.dump();
  
  exit( 0 );
}

At this point, ioctl is expecting the address of the scsi_serial structure like in the first posting. This was originally defined as struct scsi_serial sn and given to ioctl as ioctl( fd, SIOC_SERIAL, &sn). In both cases the code compiles and runs but in this modified case, it does not open the file descriptor fd and thus errors quietly. So, at this point, I cannot figure out how to replicate the behavior in the original post to this modified post.

Any help is greatly appreciated.

Thanks,

DeadPoet

One more update:

CSIOC_SERIAL should be

Code:

/* CHANGE_MADE_HERE */
/* ioctl Now does not open the device */
    if ( ( ret = ioctl( fd, SIOC_SERIAL, &(*this) ) ) != 0 ){
	perror( "SIOC_SERIAL ERROR" );
	return ( -1 );
    }

Sorry,

DeadPoet

Put device_name after all the original scsi_serial members in CdskInfo.

The memory layout of CdskInfo and scsi_serial must be identical for the first sizeof(scsi_serial) bytes.

gg

Cool , If I remove the device_name then It does compile and run, without the device_name. However, I need the device_name and I need to add additional structures into this class. Any ideas ?

Thanks You are the MAN,

DeadPoet

Here's an idea...

Originally posted by Codeplug
Put device_name after all the original scsi_serial members in CdskInfo.

The memory layout of CdskInfo and scsi_serial must be identical for the first sizeof(scsi_serial) bytes.

gg

Do you understand the memory layout of a given structure?

gg