xmlSecTransformCtx: : the pointer to user data (xmlsec and xmlsec-crypto never touch this). : the bit mask flags to control transforms execution (reserved for the future). : the bit mask flags to control transforms execution (reserved for the future). : the allowed transform data source uri types. : the list of enabled transforms; if list is empty (default) then all registered transforms are enabled. : the callback called after preparing transform chain and right before actual data processing; application can use this callback to change transforms parameters, insert additional transforms in the chain or do additional validation (and abort transform execution if needed). The transform execution context.