Allocating a DBCOMMANDTREE Structure

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The following example declares a function PctAllocNode to allocate a new DBCOMMANDTREE structure. An additional example in Setting Up a Condition Subtree uses the function.

DBCOMMANDTREE* PctAllocNode(
  DBOP op,
  DBVALUEKIND eKind,
  ULONG cbValueSize
  )
{
  DBCOMMANDTREE* pct;
  //get the OLE IMalloc interface
  IMalloc* pim;
  HRESULT hr = CoGetMalloc(MEMCTX_TASK, &pim);
  if (FAILED(hr))
    return NULL;
 
  // Allocate fixed size part of the node
  pct = (DBCOMMANDTREE*)pim->Alloc((sizeof DBCOMMANDTREE));
 
  //initialize fields
  pct->op = op;
  pct->pctFirstChild = NULL;
  pct->pctNextSibling = NULL;
  pct->hrError = S_OK;
  pct->dwKind = eKind;
 
  // Allocate variable size part of the node 
  if ( 0 != cbValueSize )
    pct.value.pvValue = (void *) pim->Alloc(cbValueSize);
 
  //Initialize value space
  if (0 != cbValueSize)
    memset(pct->value.pvValue, 0, cbValueSize);
 
  return pct;
}