Type-specified message keys for join_node
To enable this feature, define the
TBB_PREVIEW_FLOW_GRAPH_FEATURES
macro to 1.Description
The extension allows a key matching
join_node
to obtain keys via functions associated with
its input types. The extension simplifies the existing approach by removing the need to
provide a function object for each input port of join_node
.API
Header
#include "oneapi/tbb/flow_graph.h"Syntax
The extension adds a special constructor to the
join_node
interface when the
key_matching<typename K, class KHash=tbb_hash_compare>
policy is
used. The constructor has the following signature:join_node( graph &g )When constructed this way, a
join_node
calls the
key_from_message
function for each incoming message to obtain the key associated
with it. The default implementation of key_from_message
is the followingnamespace oneapi {
namespace tbb {
namespace flow {
template <typename K, typename T>
K key_from_message( const T &t ) {
return t.key();
}
}
}
}T
is one of the user-provided types in OutputTuple
and is
used to construct the join_node
, and K
is the key type
of the node.
By default, the key()
method defined in the message class will be called.
Alternatively, the user can define its own key_from_message
function in the
same namespace with the message type. This function will be found via C++ argument-dependent
lookup and used in place of the default implementation.