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//
// ENUMFORMAT.CPP
//
// By J Brown 2004
//
// www.catch22.net
//
// Implementation of the IEnumFORMATETC interface
//
// For Win2K and above look at the SHCreateStdEnumFmtEtc API call!!
//
// Apparently the order of formats in an IEnumFORMATETC object must be
// the same as those that were stored in the clipboard
//
//
//#define STRICT
#include "stdafx.h"
class CEnumFormatEtc : public IEnumFORMATETC
{
public:
//
// IUnknown members
//
HRESULT __stdcall QueryInterface(REFIID iid, void ** ppvObject);
ULONG __stdcall AddRef(void);
ULONG __stdcall Release(void);
//
// IEnumFormatEtc members
//
HRESULT __stdcall Next(ULONG celt, FORMATETC * rgelt, ULONG * pceltFetched);
HRESULT __stdcall Skip(ULONG celt);
HRESULT __stdcall Reset(void);
HRESULT __stdcall Clone(IEnumFORMATETC ** ppEnumFormatEtc);
//
// Construction / Destruction
//
CEnumFormatEtc(FORMATETC *pFormatEtc, int nNumFormats);
~CEnumFormatEtc();
private:
LONG m_lRefCount; // Reference count for this COM interface
ULONG m_nIndex; // current enumerator index
ULONG m_nNumFormats; // number of FORMATETC members
FORMATETC * m_pFormatEtc; // array of FORMATETC objects
};
//
// "Drop-in" replacement for SHCreateStdEnumFmtEtc. Called by CDataObject::EnumFormatEtc
//
HRESULT CreateEnumFormatEtc(UINT nNumFormats, FORMATETC *pFormatEtc, IEnumFORMATETC **ppEnumFormatEtc)
{
if (nNumFormats == 0 || pFormatEtc == nullptr || ppEnumFormatEtc == nullptr)
return E_INVALIDARG;
*ppEnumFormatEtc = new CEnumFormatEtc(pFormatEtc, nNumFormats);
return (*ppEnumFormatEtc) ? S_OK : E_OUTOFMEMORY;
}
//
// Helper function to perform a "deep" copy of a FORMATETC
//
static void DeepCopyFormatEtc(FORMATETC *dest, FORMATETC *source)
{
// copy the source FORMATETC into dest
*dest = *source;
if (source->ptd) {
// allocate memory for the DVTARGETDEVICE if necessary
dest->ptd = (DVTARGETDEVICE*)CoTaskMemAlloc(sizeof(DVTARGETDEVICE));
// copy the contents of the source DVTARGETDEVICE into dest->ptd
*(dest->ptd) = *(source->ptd);
}
}
//
// Constructor
//
CEnumFormatEtc::CEnumFormatEtc(FORMATETC *pFormatEtc, int nNumFormats)
{
m_lRefCount = 1;
m_nIndex = 0;
m_nNumFormats = nNumFormats;
m_pFormatEtc = new FORMATETC[nNumFormats];
// copy the FORMATETC structures
for (int i = 0; i < nNumFormats; i++) {
DeepCopyFormatEtc(&m_pFormatEtc[i], &pFormatEtc[i]);
}
}
//
// Destructor
//
CEnumFormatEtc::~CEnumFormatEtc()
{
if (m_pFormatEtc) {
for (ULONG i = 0; i < m_nNumFormats; i++) {
if (m_pFormatEtc[i].ptd)
CoTaskMemFree(m_pFormatEtc[i].ptd);
}
delete[] m_pFormatEtc;
}
}
//
// IUnknown::AddRef
//
ULONG __stdcall CEnumFormatEtc::AddRef(void)
{
// increment object reference count
return InterlockedIncrement(&m_lRefCount);
}
//
// IUnknown::Release
//
ULONG __stdcall CEnumFormatEtc::Release(void)
{
// decrement object reference count
LONG count = InterlockedDecrement(&m_lRefCount);
if (count == 0) {
delete this;
return 0;
}
else {
return count;
}
}
//
// IUnknown::QueryInterface
//
HRESULT __stdcall CEnumFormatEtc::QueryInterface(REFIID iid, void **ppvObject)
{
// check to see what interface has been requested
if (iid == IID_IEnumFORMATETC || iid == IID_IUnknown) {
AddRef();
*ppvObject = this;
return S_OK;
}
else {
*ppvObject = nullptr;
return E_NOINTERFACE;
}
}
//
// IEnumFORMATETC::Next
//
// If the returned FORMATETC structure contains a non-null "ptd" member, then
// the caller must free this using CoTaskMemFree (stated in the COM documentation)
//
HRESULT __stdcall CEnumFormatEtc::Next(ULONG celt, FORMATETC *pFormatEtc, ULONG * pceltFetched)
{
ULONG copied = 0;
// validate arguments
if (celt == 0 || pFormatEtc == nullptr)
return E_INVALIDARG;
// copy FORMATETC structures into caller's buffer
while (m_nIndex < m_nNumFormats && copied < celt) {
DeepCopyFormatEtc(&pFormatEtc[copied], &m_pFormatEtc[m_nIndex]);
copied++;
m_nIndex++;
}
// store result
if (pceltFetched != nullptr)
*pceltFetched = copied;
// did we copy all that was requested?
return (copied == celt) ? S_OK : S_FALSE;
}
//
// IEnumFORMATETC::Skip
//
HRESULT __stdcall CEnumFormatEtc::Skip(ULONG celt)
{
m_nIndex += celt;
return (m_nIndex <= m_nNumFormats) ? S_OK : S_FALSE;
}
//
// IEnumFORMATETC::Reset
//
HRESULT __stdcall CEnumFormatEtc::Reset(void)
{
m_nIndex = 0;
return S_OK;
}
//
// IEnumFORMATETC::Clone
//
HRESULT __stdcall CEnumFormatEtc::Clone(IEnumFORMATETC ** ppEnumFormatEtc)
{
HRESULT hResult;
// make a duplicate enumerator
hResult = CreateEnumFormatEtc(m_nNumFormats, m_pFormatEtc, ppEnumFormatEtc);
if (hResult == S_OK) {
// manually set the index state
((CEnumFormatEtc *)*ppEnumFormatEtc)->m_nIndex = m_nIndex;
}
return hResult;
}
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