EncodedPolyline: Added encode() method

The write() method will follow in the next commit.

lib/OpenLayers/Format/EncodedPolyline.js

@@ -130,5 +130,80 @@ OpenLayers.Format.EncodedPolyline = OpenLayers.Class(OpenLayers.Format, {
         return points;
     },
 
+    /**
+     * Method: encode
+     * Serialize an array of n-dimensional points and return an encoded string
+     *
+     * Parameters:
+     * points - {Array(Array(int))} An array containing n-dimensional
+     *          arrays of coordinates
+     * dims - {int} The dimension of the points that should be read
+     *
+     * Returns:
+     * {String} An encoded string
+     */
+    encode: function (points, dims) {
+        var encoded_points = "";
+
+        var lastPoint = new Array(dims);
+        for (var i = 0; i < lastPoint.length; ++i)
+            lastPoint[i] = 0;
+
+        for (var i = 0; i < points.length; i++) {
+            var point = points[i];
+
+            for (var dim = 0; dim < lastPoint.length; ++dim) {
+                var delta = point[dim] - lastPoint[dim];
+                encoded_points += this.encodeSignedNumber(delta);
+            }
+
+            lastPoint = point;
+        }
+        return encoded_points;
+    },
+
+    /**
+     * Method: encodeSignedNumber
+     * Encode one single signed integer and return an encoded string
+     *
+     * Parameters:
+     * num - {int} A signed integer that should be encoded
+     *
+     * Returns:
+     * {String} An encoded string
+     */
+    encodeSignedNumber: function (num) {
+        var sgn_num = num << 1;
+        if (num < 0)
+            sgn_num = ~(sgn_num);
+
+        return this.encodeNumber(sgn_num);
+    },
+
+    /**
+     * Method: encodeNumber
+     * Encode one single unsigned integer and return an encoded string
+     *
+     * encodeSignedNumber should be used instead of using this method directly!
+     *
+     * Parameters:
+     * num - {int} An unsigned integer that should be encoded
+     *
+     * Returns:
+     * {String} An encoded string
+     */
+    encodeNumber: function (num) {
+        var encodeString = "";
+        var value;
+        while (num >= 0x20) {
+            value = (0x20 | (num & 0x1f)) + 63;
+            encodeString += (String.fromCharCode(value));
+            num >>= 5;
+        }
+        value = num + 63;
+        encodeString += (String.fromCharCode(value));
+        return encodeString;
+    },
+
     CLASS_NAME: "OpenLayers.Format.EncodedPolyline"
 });