初始化来自IStream的IFilter

Question

我正在使用IFilter来索引一些MS Office文档。从文件加载是可以的，所有工作都很好，就像在所有手册和示例中一样：

HRESULT hr_f = LoadIFilter(filename, 0, (void **)&pFilter);

但是，使用BindIFilterFromStream接口失败了，我不知道如何正确使用它。

HRESULT hr_ss = BindIFilterFromStream(spStream/*my IStream* impl*/, 0, (void **)&pFilter);

我实现了IStream接口，只有在初始化期间调用的方法(IUnknown除外)是：

HRESULT StreamFilter::Stat(STATSTG * pstatstg, DWORD grfStatFlag)
{
   //Microsoft Office Ifilter from Windows Registry
   const IID CLSID_IFilter = {
       0xf07f3920,
       0x7b8c,
       0x11cf,
       { 0x9b, 0xe8, 0x00, 0xaa, 0x00, 0x4b, 0x99, 0x86 }

       //{f07f3920-7b8c-11cf-9be8-00aa004b9986}
   };
   LARGE_INTEGER pSize;
   int fl = GetFileSizeEx(_hFile, &pSize);
   memset(pstatstg, 0, sizeof(STATSTG));
   pstatstg->clsid = CLSID_IFilter;
   pstatstg->type = STGTY_STREAM;
   pstatstg->cbSize.QuadPart = pSize.QuadPart;

   return S_OK;
}

在那之后，hr_ss是E_FAIL，IFilter是NULL。

有case Using IFilter in C#，这些方法也只适用于c++中的*.pdf，但不适用于MSO文档...

Answer 1

我想出了如何正确初始化IFilter，下面是代码：

HRESULT hr = LoadIFilter(L".doc", 0, (void **)&pFilter);
IPersistStream *stream;
HRESULT hr_qi = pFilter->QueryInterface(&stream);

std::ifstream ifs(filename, ios::binary);
std::string content((std::istreambuf_iterator<char>(ifs)),
    (std::istreambuf_iterator<char>()));

IStream *comStream;
HGLOBAL hMem = ::GlobalAlloc(GMEM_MOVEABLE, content.size());
LPVOID pDoc = ::GlobalLock(hMem);
memcpy(pDoc, content.c_str(), content.size());
::GlobalUnlock(hMem);
HRESULT hr_mem = ::CreateStreamOnHGlobal(hMem, true, &comStream);
HRESULT hr_stream_load = stream->Load(comStream);

从文档中获取文本就像从MSDN中获取通常的示例一样

if (SUCCEEDED(hr))
{
  DWORD flags = 0;
  HRESULT hr = pFilter->Init(IFILTER_INIT_INDEXING_ONLY |
                             IFILTER_INIT_APPLY_INDEX_ATTRIBUTES |
                             IFILTER_INIT_APPLY_CRAWL_ATTRIBUTES |
                             IFILTER_INIT_FILTER_OWNED_VALUE_OK |
                             IFILTER_INIT_APPLY_OTHER_ATTRIBUTES,
                             0, 0, &flags);
  if (FAILED(hr))
  {
     pFilter->Release();
     throw exception("IFilter::Init() failed");
  }

  Start();

  STAT_CHUNK stat;
  while (SUCCEEDED(hr = pFilter->GetChunk(&stat)))
  {
     if ((stat.flags & CHUNK_TEXT) != 0)
        ProcessTextChunk(pFilter, stat);

     if ((stat.flags & CHUNK_VALUE) != 0)
        ProcessValueChunk(pFilter, stat);
  }

  Finish();

  pFilter->Release();      
}
else
{
  throw exception("LoadIFilter() failed");
}

你不需要实现你自己的IStream，只需要从你的缓冲区初始化它就可以了。