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<br />Initialization <br /> <br />Points of interest <br /> <br />structure_record <br /> <br />The in-memory graph is initialized by reading arcs out of the Arc/Info network <br />coverage. As arcs are read from the binary ArclInfo file, they are added to the graph. <br />The following example steps though the first few iterations of initialization: <br /> <br />I. Stream_network_head is set to NULL. <br /> <br />2. An arc is read from the ArclInfo binary file, with these attributes: <br /> <br />to_node <br />to_node <br />length <br />line_id <br />reach_id <br /> <br />3. A search is performed for the to_node. If found, it is referenced in the follow- <br />ing associations. If it is not found it is created and added to the node list. <br /> <br />4. A search is performed for the from_node. Iffound, it is referenced in the fol- <br />lowing associations. If it is not found it is created and added to the node list. <br /> <br />5. A check is performed to see if the to_node is connected downstream. If it is, <br />the initialization fails, since a node cannot have two downstream connections. If <br />it is not, a downstream connection is created. This connection (a <br />node_l ink_pair) is initialized to point to the from_node (the node <br />downstream from the to_node), but points to no reach at this time. <br /> <br />6. A new reach is created, corresponding to the current arc. The downstream Con- <br />nection of the to_node is set to point to the new reach. <br /> <br />7. A check is performed to see if the from_node is connected upstream. In either <br />case, an upstream connection is created (a node_l ink_pair). The new <br />node_l ink_pair is initialized to point to the to_node, since it is the node <br />upstream from the from_node. If the from_node was already connected <br />upstream, that node is flagged as being a confluence and the new <br />node_link-f'air is added to the node's list of upstream connections. Other- <br />wise, the new node_l ink_pair is simply used to initialize the node's list of <br />upstream connections. <br /> <br />8. The new node_l ink_pair (the from_node 's upstream connection) is set <br />to point to the previously-created reach, which corresponds to the current arc. <br /> <br />9. Steps 2 through 8 are repeated until all arcs have been read from the ArclInfo <br />binary file. <br /> <br />Modeled points of interest such as structures and stream gauges have associated data <br />stored in the in-memory network graph. Attached to the graph at nodes, these points <br />are read from the ArclInfo structures and stream gauges coverages. Each node is an <br />instance of the node_record struct. <br /> <br />The description member of the node_record struct points to a linked list of <br />node_type_description records (which contain a union of the two structures: <br />structure_record and strearngage_cell). <br /> <br />typedef <br /> <br />short <br />short <br /> <br />short <br />node location <br /> <br />struct structure rec struct <br /> <br />structure_number; <br />water_district; <br /> <br />structure~id; <br />location: <br /> <br />12 <br />