Adding support for empty geometries

lib/adapters/GPX.class.php

@@ -32,6 +32,7 @@ public function read($gpx) {
    * @return string The GPX string representation of the input geometries
    */
   public function write(Geometry $geometry) {
+    if ($geometry->isEmpty()) return NULL;
     return '<gpx creator="geoPHP" version="1.0">'.$this->geometryToGPX($geometry).'</gpx>';
   }
 

lib/adapters/WKB.class.php

@@ -14,6 +14,10 @@
 class WKB extends GeoAdapter
 {
 
+  private $dimension = 2;
+  private $z = FALSE;
+  private $m = FALSE;
+
   /**
    * Read WKB into geometry objects
    *
@@ -44,6 +48,15 @@ function getGeometry(&$mem) {
       throw new Exception('Only NDR (little endian) SKB format is supported at the moment');
     }
 
+    if ($base_info['z']) {
+      $this->dimension++;
+      $this->z = TRUE;
+    }
+    if ($base_info['m']) {
+      $this->dimension++;
+      $this->m = TRUE;
+    }
+
     // If there is SRID information, ignore it - use EWKB Adapter to get SRID support
     if ($base_info['s']) {
       fread($mem, 4);
@@ -68,16 +81,19 @@ function getGeometry(&$mem) {
   }
 
   function getPoint(&$mem) {
-    $point_coords = unpack("d*", fread($mem,16));
+    $point_coords = unpack("d*", fread($mem,$this->dimension*8));
     return new Point($point_coords[1],$point_coords[2]);
   }
 
   function getLinstring(&$mem) {
     // Get the number of points expected in this string out of the first 4 bytes
     $line_length = unpack('L',fread($mem,4));
 
+    // Return an empty linestring if there is no line-length
+    if (!$line_length[1]) return new LineString();
+
     // Read the nubmer of points x2 (each point is two coords) into decimal-floats
-    $line_coords = unpack('d'.$line_length[1]*2, fread($mem,$line_length[1]*16));
+    $line_coords = unpack('d*', fread($mem,$line_length[1]*$this->dimension*8));
 
     // We have our coords, build up the linestring
     $components = array();

lib/adapters/WKT.class.php

@@ -69,6 +69,10 @@ private function parsePoint($data_string) {
 
   private function parseLineString($data_string) {
     $data_string = $this->trimParens($data_string);
+
+    // If it's marked as empty, then return an empty line
+    if ($data_string == 'EMPTY') return new LineString();
+
     $parts = explode(',',$data_string);
     $points = array();
     foreach ($parts as $part) {
@@ -79,6 +83,10 @@ private function parseLineString($data_string) {
 
   private function parsePolygon($data_string) {
     $data_string = $this->trimParens($data_string);
+
+    // If it's marked as empty, then return an empty polygon
+    if ($data_string == 'EMPTY') return new Polygon();
+
     $parts = explode('),(',$data_string);
     $lines = array();
     foreach ($parts as $part) {
@@ -91,6 +99,10 @@ private function parsePolygon($data_string) {
 
   private function parseMultiPoint($data_string) {
     $data_string = $this->trimParens($data_string);
+
+    // If it's marked as empty, then return an empty MutiPoint
+    if ($data_string == 'EMPTY') return new MultiPoint();
+
     $parts = explode(',',$data_string);
     $points = array();
     foreach ($parts as $part) {
@@ -101,6 +113,10 @@ private function parseMultiPoint($data_string) {
 
   private function parseMultiLineString($data_string) {
     $data_string = $this->trimParens($data_string);
+
+    // If it's marked as empty, then return an empty multi-linestring
+    if ($data_string == 'EMPTY') return new MultiLineString();
+
     $parts = explode('),(',$data_string);
     $lines = array();
     foreach ($parts as $part) {
@@ -114,6 +130,10 @@ private function parseMultiLineString($data_string) {
 
   private function parseMultiPolygon($data_string) {
     $data_string = $this->trimParens($data_string);
+
+    // If it's marked as empty, then return an empty multi-polygon
+    if ($data_string == 'EMPTY') return new MultiPolygon();
+
     $parts = explode(')),((',$data_string);
     $polys = array();
     foreach ($parts as $part) {
@@ -127,6 +147,10 @@ private function parseMultiPolygon($data_string) {
 
   private function parseGeometryCollection($data_string) {
     $data_string = $this->trimParens($data_string);
+
+    // If it's marked as empty, then return an empty geom-collection
+    if ($data_string == 'EMPTY') return new GeometryCollection();
+
     $geometries = array();
     $matches = array();
     $str = preg_replace('/,\s*([A-Za-z])/', '|$1', $data_string);
@@ -179,7 +203,10 @@ public function write(Geometry $geometry) {
       return $writer->write($geometry->geos());
     }
 
-    if ($data = $this->extractData($geometry)) {
+    if ($geometry->isEmpty()) {
+      return strtoupper($geometry->geometryType()).' EMPTY';
+    }
+    else if ($data = $this->extractData($geometry)) {
       return strtoupper($geometry->geometryType()).' ('.$data.')';
     }
   }

lib/geometry/Collection.class.php

@@ -17,19 +17,18 @@ abstract class Collection extends Geometry
    *
    * @param array $components array of geometries
    */
-  public function __construct(array $components) {
+  public function __construct($components = array()) {
+    if (!is_array($components)) {
+      throw new Exception("Component geometries must be passed as an array");
+    }
     foreach ($components as $component) {
       if ($component instanceof Geometry) {
         $this->components[] = $component;
       }
       else {
-        throw new Exception("Cannot create empty collection");
+        throw new Exception("Cannot create a collection with non-geometries");
       }
     }
-
-    if (empty($this->components)) {
-      throw new Exception("Cannot create empty ".get_called_class());
-    }
   }
 
   /**
@@ -177,6 +176,18 @@ public function dimension() {
     return $dimension;
   }
 
+  // A collection is empty if it has no components OR all it's components are empty
+  public function isEmpty() {
+    if (!count($this->components)) {
+      return TRUE;
+    }
+    else {
+      foreach ($this->components as $component) {
+        if (!$component->isEmpty()) return FALSE;
+      }
+      return TRUE;
+    }
+  }
 
   // Not valid for this geometry type
   // --------------------------------

lib/geometry/Geometry.class.php

@@ -29,7 +29,7 @@ abstract public function exteriorRing();
   abstract public function numInteriorRings();
   abstract public function interiorRingN($n);
   abstract public function dimension();
-
+  abstract public function isEmpty();
 
   // Abtract: Non-Standard
   // ---------------------
@@ -315,11 +315,6 @@ public function isMeasured() {
     return FALSE;
   }
 
-  public function isEmpty() {
-    // geoPHP does not yet support empty geometries
-    return FALSE;
-  }
-
   public function coordinateDimension() {
     // geoPHP only supports 2-dimentional space
     return 2;

lib/geometry/LineString.class.php

@@ -13,9 +13,9 @@ class LineString extends Collection
    * @param array $points An array of at least two points with
    * which to build the LineString
    */
-  public function __construct(array $points) {
-    if (count($points) < 2) {
-      throw new Exception("Cannot construct LineString with less than two points");
+  public function __construct($points = array()) {
+    if (count($points) == 1) {
+      throw new Exception("Cannot construct a LineString with a single point");
     }
 
     // Call the Collection constructor to build the LineString

lib/geometry/Point.class.php

@@ -110,6 +110,10 @@ public function dimension() {
     return 0;
   }
 
+  public function isEmpty() {
+    return FALSE;
+  }
+
   // Not valid for this geometry type
   public function numGeometries()    { return NULL; }
   public function geometryN($n)      { return NULL; }