Command
QisLib_GetStructureRoot

QisLib_GetStructureRoot

Function:
	int QisLib_GetStructureRoot(char*** TopStructListPtr);

Inputs:
	TopStructListPtr: Address of pointer of type char**. When the function returns
	successfully, this pointer will point to a list of top cell names.

Return:
	success: value > 0 indicating the number of top cell names returned in the list.
	failure: value <= 0 indicating one of the following errors :

Errors:
	0: No top cells found, either no GDSII/OASIS file opened or invalid file.
	-1: Input argument is invalid (null).
	-2: Internal memory error occurred while generating list of top cells.
	-3: File open in progress, operation not permitted.

Description:
	- Gets a list of top cell names present in the file.
	- A top cell is any cell that is not referenced by any of other cells.
	- It is the responsibility of the user to ensure that the memory allocated for the
	list is freed by a call to QisLib_FreeStructureList.
	- The top cells are listed in the order of decreasing depth in the cell hierarchy.
	Hence the deepest cell is listed first.

Example:
	char** List;
	Ret = QisLib_GetStructureRoot(&List);
	...
	...
	if(Ret > 0)
	QisLib_FreeStructureList(List,Ret);