From e84cd533b1d1ec056f17cd6117de1ee93e6157a4 Mon Sep 17 00:00:00 2001
From: Sandro Santilli <strk@keybit.net>
Date: Tue, 24 Aug 2004 15:50:04 +0000
Subject: [PATCH] PointN() ported.

git-svn-id: http://svn.osgeo.org/postgis/trunk@740 b70326c6-7e19-0410-871a-916f4a2858ee
---
 lwgeom/MISSING_OBJECTS  |  1 -
 lwgeom/lwgeom_ogc.c     | 62 +++++++++++++++++++++++++++++++++++++++++
 lwgeom/lwpostgis.sql.in | 17 ++++++++---
 3 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/lwgeom/MISSING_OBJECTS b/lwgeom/MISSING_OBJECTS
index 661a298f2..3572c5af8 100644
--- a/lwgeom/MISSING_OBJECTS
+++ b/lwgeom/MISSING_OBJECTS
@@ -28,7 +28,6 @@ FUNC: KEEPING FUNCTION: [envelope(geometry)]
 FUNC: KEEPING FUNCTION: [x(geometry)]
 FUNC: KEEPING FUNCTION: [y(geometry)]
 FUNC: KEEPING FUNCTION: [z(geometry)]
-FUNC: KEEPING FUNCTION: [pointn(geometry, integer)]
 FUNC: KEEPING FUNCTION: [max_distance(geometry, geometry)]
 FUNC: KEEPING FUNCTION: [optimistic_overlap(geometry, geometry, double precision)]
 FUNC: KEEPING FUNCTION: [segmentize(geometry, double precision)]
diff --git a/lwgeom/lwgeom_ogc.c b/lwgeom/lwgeom_ogc.c
index 87954e9f4..818957937 100644
--- a/lwgeom/lwgeom_ogc.c
+++ b/lwgeom/lwgeom_ogc.c
@@ -41,6 +41,8 @@ Datum LWGEOM_exteriorring_polygon(PG_FUNCTION_ARGS);
 Datum LWGEOM_interiorringn_polygon(PG_FUNCTION_ARGS);
 // ---- NumInteriorRings(geometry)
 Datum LWGEOM_numinteriorrings_polygon(PG_FUNCTION_ARGS);
+// ---- PointN(geometry, integer)
+Datum LWGEOM_pointn_linestring(PG_FUNCTION_ARGS);
 
 
 // internal
@@ -387,6 +389,7 @@ Datum LWGEOM_interiorringn_polygon(PG_FUNCTION_ARGS)
 		pfree_inspected(inspected);
 		PG_RETURN_NULL();
 	}
+	pfree_inspected(inspected);
 
 	ring = poly->rings[wanted_index+1];
 
@@ -406,3 +409,62 @@ Datum LWGEOM_interiorringn_polygon(PG_FUNCTION_ARGS)
 	PG_RETURN_POINTER(result);
 }
 
+// PointN(GEOMETRY,INTEGER) -- find the first linestring in GEOMETRY,
+// return the point at index INTEGER (0 is 1st point).  Return NULL if
+// there is no LINESTRING(..) in GEOMETRY or INTEGER is out of bounds.
+PG_FUNCTION_INFO_V1(LWGEOM_pointn_linestring);
+Datum LWGEOM_pointn_linestring(PG_FUNCTION_ARGS)
+{
+	LWGEOM *geom;
+	int32 wanted_index;
+	LWGEOM_INSPECTED *inspected;
+	LWLINE *line = NULL;
+	POINTARRAY *pts;
+	LWPOINT *point;
+	char *serializedpoint;
+	LWGEOM *result;
+	int i;
+
+	wanted_index = PG_GETARG_INT32(1);
+	if ( wanted_index < 0 )
+		PG_RETURN_NULL(); // index out of range
+
+	geom = (LWGEOM *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
+	inspected = lwgeom_inspect(SERIALIZED_FORM(geom));
+
+	for (i=0; i<inspected->ngeometries; i++)
+	{
+		line = lwgeom_getline_inspected(inspected, i);
+		if ( line ) break;
+	}
+
+	if ( line == NULL ) PG_RETURN_NULL();
+
+	// Ok, now we have a line. Let's see if it has enough points.
+	if ( wanted_index > line->points->npoints-1 )
+	{
+		pfree_inspected(inspected);
+		PG_RETURN_NULL();
+	}
+	pfree_inspected(inspected);
+
+	// Construct a point array
+	pts = pointArray_construct(getPoint(line->points, wanted_index),
+		line->points->ndims, 1);
+
+	// Construct an LWPOINT
+	point = lwpoint_construct(line->points->ndims, lwgeom_getSRID(geom),
+		pts);
+
+	// Serialized the point
+	serializedpoint = lwpoint_serialize(point);
+
+	// And we construct the line (copy again)
+	result = LWGEOM_construct(serializedpoint, lwgeom_getSRID(geom),
+		lwgeom_hasBBOX(geom->type));
+
+	pfree(point);
+	pfree(serializedpoint);
+
+	PG_RETURN_POINTER(result);
+}
diff --git a/lwgeom/lwpostgis.sql.in b/lwgeom/lwpostgis.sql.in
index a72e77e76..2092253f6 100644
--- a/lwgeom/lwpostgis.sql.in
+++ b/lwgeom/lwpostgis.sql.in
@@ -11,6 +11,9 @@
 --  
 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 -- $Log$
+-- Revision 1.13  2004/08/24 15:50:04  strk
+-- PointN() ported.
+--
 -- Revision 1.12  2004/08/24 15:05:34  strk
 -- Added NumInteriorRings() and InteriorRingN()
 --
@@ -885,14 +888,20 @@ CREATEFUNCTION InteriorRingN(geometry,integer)
 	AS '@MODULE_FILENAME@','LWGEOM_interiorringn_polygon'
 	LANGUAGE 'C' WITH (isstrict);
 
-
-------------------------------------------------------------------------
-
-CREATEFUNCTION geometrytype(geometry)
+CREATEFUNCTION GeometryType(geometry)
 	RETURNS text
 	AS '@MODULE_FILENAME@', 'LWGEOM_getTYPE'
 	LANGUAGE 'C' WITH (isstrict);
 
+CREATEFUNCTION PointN(geometry,integer)
+	RETURNS geometry
+	AS '@MODULE_FILENAME@','LWGEOM_pointn_linestring'
+	LANGUAGE 'C' WITH (isstrict);
+
+
+
+------------------------------------------------------------------------
+
 --
 -- Aggregate functions
 --
-- 
2.40.0