From fcf32c2ccfb0a8135d8e1d4adca41de6793c0302 Mon Sep 17 00:00:00 2001
From: Sandro Santilli <strk@keybit.net>
Date: Tue, 16 Aug 2005 21:38:18 +0000
Subject: [PATCH] Added M(point) function

git-svn-id: http://svn.osgeo.org/postgis/trunk@1871 b70326c6-7e19-0410-871a-916f4a2858ee
---
 CHANGES                 |  1 +
 lwgeom/lwgeom_ogc.c     | 41 +++++++++++++++++++++++++++++++++++++++++
 lwgeom/lwpostgis.sql.in |  5 +++++
 3 files changed, 47 insertions(+)

diff --git a/CHANGES b/CHANGES
index c68e336f5..85264b6d0 100644
--- a/CHANGES
+++ b/CHANGES
@@ -13,6 +13,7 @@ PostGIS 1.1.0CVS
 	- initial implementation of postgis_proc_upgrade script
 	- NEW line_substring() function
 	- NEW line_locate_point() function
+	- New M(point) function
 	- JTS support improvements
 	- Chunked GeomUnion implementation (much faster)
 
diff --git a/lwgeom/lwgeom_ogc.c b/lwgeom/lwgeom_ogc.c
index f68e6243b..81b86c1b6 100644
--- a/lwgeom/lwgeom_ogc.c
+++ b/lwgeom/lwgeom_ogc.c
@@ -49,6 +49,8 @@ Datum LWGEOM_x_point(PG_FUNCTION_ARGS);
 Datum LWGEOM_y_point(PG_FUNCTION_ARGS);
 // ---- Z(geometry)
 Datum LWGEOM_z_point(PG_FUNCTION_ARGS);
+// ---- M(geometry)
+Datum LWGEOM_m_point(PG_FUNCTION_ARGS);
 // ---- StartPoint(geometry)
 Datum LWGEOM_startpoint_linestring(PG_FUNCTION_ARGS);
 // ---- EndPoint(geometry)
@@ -661,6 +663,45 @@ Datum LWGEOM_z_point(PG_FUNCTION_ARGS)
 	PG_RETURN_FLOAT8(p.z);
 }
 
+// M(GEOMETRY) -- find the first POINT(..) in GEOMETRY, returns its M value.
+// Return NULL if there is no POINT(..) in GEOMETRY.
+// Return 0 if there is no M in this geometry.
+PG_FUNCTION_INFO_V1(LWGEOM_m_point);
+Datum LWGEOM_m_point(PG_FUNCTION_ARGS)
+{
+	PG_LWGEOM *geom;
+	LWGEOM_INSPECTED *inspected;
+	LWPOINT *point = NULL;
+	POINT3DM p;
+	int i;
+
+	geom = (PG_LWGEOM *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
+
+	// if there's no M return 0
+	if ( ! TYPE_HASM(geom->type) ) PG_RETURN_FLOAT8(0.0);
+
+	inspected = lwgeom_inspect(SERIALIZED_FORM(geom));
+
+	for (i=0; i<inspected->ngeometries; i++)
+	{
+		point = lwgeom_getpoint_inspected(inspected, i);
+		if ( point ) break;
+	}
+	pfree_inspected(inspected);
+
+	if ( point == NULL ) {
+		PG_FREE_IF_COPY(geom, 0);
+		PG_RETURN_NULL();
+	}
+
+	// Ok, now we have a point, let's get M
+	lwpoint_getPoint3dm_p(point, &p);
+
+	PG_FREE_IF_COPY(geom, 0);
+
+	PG_RETURN_FLOAT8(p.m);
+}
+
 // StartPoint(GEOMETRY) -- find the first linestring in GEOMETRY,
 // return the first point.
 // Return NULL if there is no LINESTRING(..) in GEOMETRY 
diff --git a/lwgeom/lwpostgis.sql.in b/lwgeom/lwpostgis.sql.in
index 13de5aa89..dcb85b48d 100644
--- a/lwgeom/lwpostgis.sql.in
+++ b/lwgeom/lwpostgis.sql.in
@@ -1030,6 +1030,11 @@ CREATEFUNCTION Z(geometry)
 	AS '@MODULE_FILENAME@','LWGEOM_z_point'
 	LANGUAGE 'C' _IMMUTABLE_STRICT; -- WITH (isstrict);
 
+CREATEFUNCTION M(geometry)
+	RETURNS float8
+	AS '@MODULE_FILENAME@','LWGEOM_m_point'
+	LANGUAGE 'C' _IMMUTABLE_STRICT; -- WITH (isstrict);
+
 CREATEFUNCTION StartPoint(geometry)
 	RETURNS geometry
 	AS '@MODULE_FILENAME@', 'LWGEOM_startpoint_linestring'
-- 
2.50.0