Use COM to provide SafeArray data and comsafearray data

Use COM to provide SafeArray data and comsafearray data

In the previous blog "read SafeArray data", we introduced C # To Read secure arrays. How can we compile COM?

1. Define the SAFEARRAY variable

SAFEARRAY *pSArray = NULL;

2. Release this variable

SafeArrayDestroy(pSArray);

3. Create a vector table

pSArray = SafeArrayCreateVector(VT_UI1, 0, 32);

Definition of vector variable (VT_UI1): MSDN

VT_EMPTY

Variable type is not specified.

VT_NULL

Variable type is NULL.

VT_I2

Variable type is 2-byte signed INT.

VT_I4

Variable type is 4-byte signed INT.

VT_R4

Variable type is 4-byte real.

VT_R8

Variable type is 8-byte real.

VT_CY

Variable type is currency.

VT_DATE

Variable type is date.

VT_BSTR

Variable type is binary string.

VT_DISPATCH

Variable type isIDispatchFAR *.

VT_ERROR

Variable type is SCODE.

VT_BOOL

Variable type is Boolean; True =-1, False = 0.

VT_VARIANT

Variable type isVARIANTFAR *.

VT_UNKNOWN

Variable type isIUnknownFAR *.

VT_UI1

Variable type is unsigned char.

VT_RESERVED

This element is reserved.

VT_BYREF

Variable type is a pointer to data.

VT_ARRAY

Variable type is a safe array.

4. Write Data

SafeArrayPutElement(pSArray, &l, &inqReport[l]);

Instance Program (COM method ):

AA: Shielded Value

STDMETHODIMP CRepoFmt::getInqRepo(ULONG iStation, SAFEARRAY** ret){SAFEARRAY *pSArray = NULL;unsigned char inqReport[32];unsigned char xorByte = AA;int iStationID = 0;if (iStation < 1) iStationID = 1;elseiStationID = iStation;inqReport[0]  = AA;inqReport[1]  = AA;inqReport[2]  = AA;inqReport[3]  = AA;inqReport[4]  = (iStationID % AA);inqReport[5]  = (iStationID / AA);inqReport[6]  = AA;inqReport[7]  = AA;inqReport[8]  = AA;inqReport[9]  = AA;inqReport[10] = AA;inqReport[11] = AA;for (int i = 1; i < 18; i++)xorByte ^= inqReport[i];inqReport[18] = xorByte;// Fill the inqReport etc.for (int j = 12; j < 18; j++)inqReport[j] = 0;for (int k = 19; k < 32; k++)inqReport[k] = 0;if (!ret)return E_POINTER;if (*ret) {SafeArrayDestroy(pSArray);*ret = NULL;}pSArray = SafeArrayCreateVector(VT_UI1, 0, 32);for (long l = 0; l < 32; l++)SafeArrayPutElement(pSArray, &l, &inqReport[l]);*ret = pSArray;return S_OK;}

Question about reading and writing SAFEARRAY data (COM )?

Not necessarily BSTR is installed in SAFEARRAY. It is useless that SAFEARRAY does not know its VAR_TYPE.

Teach SafeArrayGetElement usage

Example
STDMETHODIMP CEnumPoint: Next (
ULONG celt,
Variant far rgvar [],
ULONG * pceltFetched)
{
Unsigned int I;
Long ix;
HRESULT hresult;

For (I = 0; I <celt; ++ I)
VariantInit (& rgvar [I]);

For (I = 0; I <celt; ++ I ){
If (m_iCurrent = m_celts ){
Hresult = ReportResult (0, S_FALSE, 0, 0 );
Goto LDone;
}

Ix = m_iCurrent ++;
Hresult = SafeArrayGetElement (m_psa, & ix, & rgvar [I]);
If (FAILED (hresult ))
Goto LError0;
}
Hresult = NOERROR;

LDone :;
* PceltFetched = I;
Return hresult;

LError0 :;
For (I = 0; I <celt; ++ I)
VariantClear (& rgvar [I]);
Return hresult;
}