Go to DGKC docs

Search Documentation

SAFEARRAY data type

SAFEARRAY data type described below is recognized by most development environments. It is used by DG Kernel software to pass references to buffers of data to and from the user application. The structure is described blow. Normally in Microsoft Visual Studio it should not be created directly. Use SafeArrayCreate() function (See online documentation for Visual Studio) to allocate the array. Then use SafeArrayLock() to access the data in the array. Use SafeArrayUnlock() and SafeArrayDestroy() to release and delete the data.

Sample below uses IModel_DG::SaveToMemory1() method to obtain copy of persistent data of the current model as a SAFEARRAY.

void MyDialog::DoSave(CADFormat_DG format) 
{
    IModel_DGPtr iModel = m_dgk.GetModel();

    SAFEARRAY* data = nullptr;

    iModel->SaveToMemory1(format, &data); // SaveToMemory() returns the array unlocked with zero lock counter

    // Access the data in the array
    VERIFY( SafeArrayLock(data) == S_OK );

    // At this point data of the model is located at data->pvData and has length of 
    // data->rgsabound[0].cElements bytes. Do embedding the model into the application document,
    // If the format is other than .MDG it might make sense to encrypt the data to keep you models 
    // accessible by your applications only

    // Unlock the data
    VERIFY( SafeArrayUnlock(data) == S_OK );
    // Release the memory
    VERIFY( SafeArrayDestroy(data) == S_OK );
}

Sample below uses IModel_DG::LoadFromMemory1() method to reload the current model from data in a SAFEARRAY.

void MyDialog::DoLoad(int format) 
{
    IModel_DGPtr iModel = m_dgk.GetModel();

    SAFEARRAYBOUND rgsabound[1];         // One dimensional array
    rgsabound[0].lLbound = 0;                           // The lower bound is always 0
    rgsabound[0].cElements = myModelSize;     // myModelSize would be same as file.GetLength(); 
                                                                        // if the model was loaded from a model file
    // Create array of the above size
    SAFEARRAY* psa = SafeArrayCreate(VT_UI1, 1, rgsabound);

    if(psa == NULL)
        return;

    VERIFY( SafeArrayLock( psa ) == S_OK );     // Before this call the data in psa->pvData is not accessible  

    //Copy, load etc data of the model from your application into psa->pvData here

    VARIANT_BOOL success = VARIANT_FALSE;
    iModel->LoadFromMemory(format, &psa, &success);     // Pass it to the component
    ASSERT(success == VARIANT_TRUE);
    VERIFY( SafeArrayUnlock( psa ) == S_OK );     // Unlock the data/> &nbs    VERIFY( SafeArrayDestroy( psa ) == S_OK );     // Release the memory
}

This is  how the SAFEARRAY type is described in Microsoft SDK documentation:

The definition for a safearray varies, depending on the target operating system platform. On 32-bit Windows systems, both the cbElements and cLocks parameters are unsigned long integers, and the handle parameter is omitted. On 16-bit Windows systems, cbElements and cLocks are unsigned short integers The handle parameter is retained for compatibility with earlier software. For example:

typedef struct FARSTRUCT tagSAFEARRAY {

        unsigned short cDims; // Count of dimensions in this array.

        unsigned short fFeatures; // Flags used by the SafeArray. routines documented below.

        unsigned long cbElements; // Size of an element of the array.  Does not include size of pointed-to data.

        unsigned long cLocks; // Number of times the array has been. Locked without corresponding unlock.

        void HUGEP* pvData; // Pointer to the data.

        SAFEARRAYBOUND rgsabound[1]; // One bound for each dimension.

} SAFEARRAY;

Remarks
The array rgsabound is stored with the left-most dimension in rgsabound[0] and the right-most dimension in rgsabound[cDims - 1]. If an array was specified in a C-like syntax as a [2][5], it would have two elements in the rgsabound vector. Element 0 has an lLbound of 0 and a cElements of 2. Element 1 has an lLbound of 0 and a cElements of 5.

The fFeatures flags describe attributes of an array that can affect how the array is released. The fFeatures field describes what type of data is stored in the SAFEARRAY and how the array is allocated. This allows freeing the array without referencing its containing variant. The bits are accessed using the following constants:

fFeatures Flags Description 

FADF_AUTO 0x0001 An array that is allocated on the stack.

FADF_STATIC 0x0002 An array that is statically allocated.

FADF_EMBEDDED 0x0004 An array that is embedded in a structure.

FADF_FIXEDSIZE 0x0010 An array that may not be resized or reallocated.

FADF_RECORD 0x0020    An array containing records. When set there will be a pointer to the IRecordinfo interface at negative offset 4 in the array descriptor.

FADF_HAVEIID 0x0040    An array that has an IID identifying interface. When set there will be a guid at negative offset 16 in the safearray descriptor. Flag is set only when FADF_DISPATCH or FADF_UNKNOWN is also set. 

FADF_HAVEVARTYPE 0x0080    An array that has a VT type. When set there will be a VT tag at negative offset 4 in the array descriptor that specifies the element type.

FADF_BSTR 0x0100    An array of BSTRs.

FADF_UNKNOWN 0x0200    An array of IUnknown*.

FADF_DISPATCH 0x0400    An array of IDispatch*.

FADF_VARIANT 0x0800    An array of VARIANTs.

FADF_RESERVED 0xF0E8    Bits reserved for future use.

SAFEARRAYBOUND Structure

typedef struct tagSAFEARRAYBOUND {

} SAFEARRAYBOUND;