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List:       ms-atl
Subject:    STL
From:       "Perley P. Laliberte" <Perley-Laliberte () FORUM-FINANCIAL ! COM>
Date:       2001-07-13 17:41:52
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Hello,

This may be ot but I thought I may find some encouraging words from
someone, so here goes. I trying to implement a STL map that will at some
point be converted into a safearray. I have it working but the performance
is pretty slow.(I have posted several question along these lines which have
helped me narrow down my options.)
I am wondering is there some canned algorithm for doing this - this being
convert a map into a byte stream and then into a safearray?
Is there and alternative to using memcpy and how expensive is using memcpy
several time as I'm using it in the included code?

I included this code so I could hopefully get some feedback on mistakes I'm
making/not making and possible suggestions on how to improvement the
performance problem I'm confronting.


definition of STL map:

#include <map>

#include "ISSHelper.h"

using namespace std;

class x : public y
{
        typedef map<CComBSTR, CComVariant> m_MM;
 typedef m_MM::value_type m_vtM;
 m_MM m_tmMap;

*** (as an aside)
*** what do I need to add to get rid of the using namespace std?


So with this map is there a predefined algorithm that will copy the data
into a raw byte stream, array, buffer...?

I have it working presently like so any idea on better approaches are
welcomed:

HRESULT hr = S_OK;
 CISSHelper ISSHelper;

 // Store number of property name/value pairs to the stream.
 int nCount = m_tmMap.size();

        //***the write methods implementation is included at the end
 ISSHelper.Write(&nCount, sizeof(int), NULL);

 // Iterate and stream each property name/value pair to the stream.
 while (it != m_tmMap.end())
 {
  CComBSTR bstrName = bstrKey = it->first;
  CComVariant varVal = vtVal = it->second;
  hr = bstrName.WriteToStream((IStream*)&ISSHelper);
  if (FAILED(hr))
  {
   return hr;
  }

  hr = varVal.WriteToStream((IStream*)&ISSHelper);
  if (FAILED(hr))
  {
   return hr;
  }
 }
 //Database class has a set, get and delete
 PersistentData oPD;

 // Creating a safearray of variants with three elements.
   VARIANT varData;
   SAFEARRAY FAR* psa;
   SAFEARRAYBOUND rgsabound[1];
   rgsabound[0].lLbound = 0;
   rgsabound[0].cElements = ISSHelper.m_ulLength;
   psa = SafeArrayCreate(VT_UI1, 1, rgsabound);

 // Try to lock and access safe array's raw memory pointer.
 LPBYTE lpBuffer;
 hr = SafeArrayAccessData(psa,(void **)&lpBuffer);
 if (FAILED(hr))
 {
  ::SafeArrayDestroy(psa);
  return hr;
 }

 // Copy bytes from global heap to safe array.
 ISSHelper.Read(lpBuffer, ISSHelper.m_ulLength, NULL);

 hr = SafeArrayUnaccessData(psa);
 if (FAILED(hr))
  return hr;

 // Set variant to new safe array.
 varData.vt = VT_ARRAY | VT_UI1;
 varData.parray = psa;

 oPD.setSession(m_bstrConnectString, m_bstrGUID, varData);
 return hr;

this is the definition of the ISSHelper.Write that that I'm using(was in a
microsoft example of handling BLOB's or something).


HRESULT CISSHelper::Write( const void *pv, ULONG cb, ULONG* pcbWritten )
{
 // Check parameters.
 if ( !pv ) return STG_E_INVALIDPOINTER;
 if ( pcbWritten ) *pcbWritten = 0;
 if ( 0 == cb ) return S_OK;

 // Enlarge the current buffer.
 m_ulLength += cb;

 // Grow internal buffer to new size.
 while ( m_ulLength > m_ulBufSize )
 {
  m_ulBufSize += BLOCK;
  if ( m_ulLength < m_ulBufSize )
  {
   m_pBuffer = CoTaskMemRealloc( m_pBuffer,
m_ulBufSize );
  }
 }

 // Check for out of memory situation.
 if ( NULL == m_pBuffer )
 {
  Clear();
  return E_OUTOFMEMORY;
 }

 // Copy callers memory to internal bufffer and update write
position.
 memcpy( (void*)((BYTE*)m_pBuffer + m_iWritePos), pv, cb );
 m_iWritePos += cb;

 // Return bytes written to caller.
 if ( pcbWritten ) *pcbWritten = cb;

 return S_OK;
}

Any ideas, thoughts or suggestions welcomed.

Thanks,

Perl

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