Data structure used for building pseudo-topology. More...

#include <dig_structs.h>

Data Fields
int *	array
	Offset list. More...

int	array_num
	Number of items in offset list. More...

int	array_alloc
	Space allocated for offset list. More...

Detailed Description

Data structure used for building pseudo-topology.

See Vect__build_sfa() (Format_info_ogr and Format_info_pg) for implementation issues.

Definition at line 388 of file dig_structs.h.

Field Documentation

◆ array

int* Format_info_offset::array

Offset list.

Array where feature/part info is stored for each feature in GRASS. This is not used for GV_CENTROID. Because one feature may contain more elements (geometry collection also recursively), offset for one line may be stored in more records. First record is FID, next records are part indexes if necessary.

Example 1:

ring in 3. polygon in 7. feature (multipolygon) of geometry collection which has FID = 123 123 (feature 123: geometry collection) 6 (7. feature in geometry collection: multiPolygon) 2 (3. polygon) 4 (5. ring in the polygon)

Example 2: geometry collection FID '1' containing one point, one linestring and one polygon

Offset:

idx  offset note
----------------
0           1      FID
1           0      first part (point)

2           1      FID
3           1      second part (linestring)

4           1      FID
5           2      third part (polygon)
6           0      first ring of polygon

GRASS topology:

line idx
-----------------
1    0      point
2    2      line
3    4      boundary
4    1      centroid read from topo (idx == FID)

In PostGIS Topology mode the offset array is used for mapping
nodes.

Definition at line 436 of file dig_structs.h.

Referenced by V1_delete_line_ogr(), V1_delete_line_pg(), Vect__free_offset(), Vect__load_map_nodes_pg(), Vect_build_ogr(), Vect_build_pg(), Vect_fidx_dump(), Vect_open_fidx(), and Vect_save_fidx().