Tricks of the Windows Gam…ming Gurus (2nd Edition)/Disc2.iso/msdn_vcb/samples/vc98/mfc/database/daotable/database.cpp

C/C++ Source or Header | 1998-03-27 | 5.0 KB | 202 lines

// database.cpp -- MFC DAO Database specific functions
//
// This is a part of the Microsoft Foundation Classes C++ library.
// Copyright (C) 1992-1998 Microsoft Corporation
// All rights reserved.
//
// This source code is only intended as a supplement to the
// Microsoft Foundation Classes Reference and related
// electronic documentation provided with the library.
// See these sources for detailed information regarding the
// Microsoft Foundation Classes product.

//
// contains the functions that deal directly with DAODatabase
// creation, opening and closing:
//
// void closeDatabase(CDaoDatabase **ppDatabase);
//
// int openDatabase(CDaoDatabase **ppDatabase, CString fileName,
//                BOOL bReportNoOpen = TRUE);
//
// BOOL createDatabase(CDaoDatabase **ppDatabase, CString fileName,
//                int dwOptions = 0);

#include "stdafx.h"
#include "database.h"

// close the database and destruct it
// IN/OUT:: ppDatabase--pointer to pointer to database to close and
// destruct
void closeDatabase(CDaoDatabase **ppDatabase)
{
    // only process if the database object exists
    if (*ppDatabase != NULL)
    {
        if ((*ppDatabase)->IsOpen())
            (*ppDatabase)->Close();

        // closing doesn't delete the object
        delete *ppDatabase;
        *ppDatabase = NULL;
    }
}

// open the database from a file (close if necessary)
// IN/OUT: ppDatabase--pointer to pointer to database object
// IN: fileName--name of .mdb file to open
// IN: bReportNoOpen--TRUE by default, if true, if open fails
//     because the specified MDB file doesn't exist, report that
//     fact to the user.  Note: other errors are reported always
// RETURN: 1 if success, 0 if non-fatal failure, -1 if fatal failure
int openDatabase(CDaoDatabase **ppDatabase, CString fileName,
                  BOOL bReportNoOpen /* = TRUE */)
{
    // initialize success indicator
    int nReturnCode = 1;

    // close and delete if necessary
    if (*ppDatabase != NULL)
    {
        if ((*ppDatabase)->IsOpen())
            closeDatabase(ppDatabase);
        delete *ppDatabase;
    }

    // construct new database
    *ppDatabase = new CDaoDatabase;

    // failed to allocate
    if (ppDatabase == NULL)
        return -1; // fatal error

    // now open the database object with error checking
    try
    {
        (*ppDatabase)->Open(fileName);
    }
    catch (CDaoException *e)
    {
        // special case--couldn't find the file, so it may be because
        // user specified a new file to open
        if (e->m_pErrorInfo->m_lErrorCode == 3024)
        {
            if (bReportNoOpen)
            {
                // create a message to display
                CString message = _T("Couldn't open database--Exception: ");
                message += e->m_pErrorInfo->m_strDescription;

                // output status
                AfxMessageBox(message);
            }

            // indicate failure but not fatal
            nReturnCode = 0;
        }
        else // other type of DAO exception--always report
        {
            // create a message to display
            CString message = _T("Couldn't open database--Exception: ");
            message += e->m_pErrorInfo->m_strDescription;

            // output status
            AfxMessageBox(message);

            // indicate fatal error
            nReturnCode = -1;
        }

        // not rethrowing, so delete exception
        e->Delete();

        delete *ppDatabase;
        *ppDatabase = NULL;
    }
    catch (CMemoryException *e)
    {
        // output status
        AfxMessageBox(_T("Failed to open database--Memory exception thrown."));

        // not rethrowing, so delete exception
        e->Delete();

        delete *ppDatabase;
        *ppDatabase = NULL;

        // indicate fatal error
        nReturnCode = -1;
    }

    return nReturnCode;
}

// create the database file (close any open database)
// IN/OUT: ppDatabase--pointer to pointer to database object
// IN: fileName--name of .mdb file to open
// IN: dwOptions--info like version and encryption settings
//     0 by default
// RETURN: TRUE if success, FALSE if failure
BOOL createDatabase(CDaoDatabase **ppDatabase, CString fileName,
                  int dwOptions /* = 0 */)
{
    // initialize success indicator
    BOOL bSuccess = TRUE;

    // close and delete if necessary
    if (*ppDatabase != NULL)
    {
        if ((*ppDatabase)->IsOpen())
            closeDatabase(ppDatabase);
        delete *ppDatabase;
    }

    // construct new database
    *ppDatabase = new CDaoDatabase;

    // failed to allocate
    if (ppDatabase == NULL)
        return FALSE; // error

    // now create the database object with error checking
    try
    {
        // default language specified
        (*ppDatabase)->Create(fileName, dbLangGeneral, dwOptions);
    }
    catch (CDaoException *e)
    {
        // create a message to display
        CString message = _T("Couldn't create database--Exception: ");
        message += e->m_pErrorInfo->m_strDescription;

        // output status
        AfxMessageBox(message);

        // not rethrowing, so delete exception
        e->Delete();

        delete *ppDatabase;
        *ppDatabase = NULL;

        // failure
        bSuccess = FALSE;
    }
    catch (CMemoryException *e)
    {
        // output status
        AfxMessageBox(_T("Failed to create database--Memory exception thrown."));

        // not rethrowing, so delete exception
        e->Delete();

        delete *ppDatabase;
        *ppDatabase = NULL;

        // failure
        bSuccess = FALSE;
    }

    return bSuccess;
}