polyline: Added decodeSigned/UnsignedInteger() functions

src/ol/parser/polyline.js

@@ -16,6 +16,18 @@ ol.parser.polyline.encodeSignedInteger = function(num) {
 };
 
 
+/**
+ * Decode one single signed integer from an encoded string
+ *
+ * @param {string} encoded An encoded string.
+ * @return {number} The decoded signed integer.
+ */
+ol.parser.polyline.decodeSignedInteger = function(encoded) {
+  var result = ol.parser.polyline.decodeUnsignedInteger(encoded);
+  return ((result & 1) ? ~(result >> 1) : (result >> 1));
+};
+
+
 /**
  * Encode one single unsigned integer and return an encoded string
  *
@@ -33,3 +45,24 @@ ol.parser.polyline.encodeUnsignedInteger = function(num) {
   encodeString += (String.fromCharCode(value));
   return encodeString;
 };
+
+
+/**
+ * Decode one single unsigned integer from an encoded string
+ *
+ * @param {string} encoded An encoded string.
+ * @return {number} The decoded unsigned integer.
+ */
+ol.parser.polyline.decodeUnsignedInteger = function(encoded) {
+  var result = 0;
+  var shift = 0;
+
+  var b, i = 0;
+  do {
+    b = encoded.charCodeAt(i++) - 63;
+    result |= (b & 0x1f) << shift;
+    shift += 5;
+  } while (b >= 0x20);
+
+  return result;
+};

test/spec/ol/parser/polyline.test.js

@@ -20,6 +20,24 @@ describe('ol.parser.polyline', function() {
     });
   });
 
+  describe('decodeSignedInteger', function() {
+    it('returns expected value', function() {
+      var decodeSignedInteger = ol.parser.polyline.decodeSignedInteger;
+
+      expect(decodeSignedInteger('?')).toEqual(0);
+      expect(decodeSignedInteger('@')).toEqual(-1);
+      expect(decodeSignedInteger('A')).toEqual(1);
+      expect(decodeSignedInteger('B')).toEqual(-2);
+      expect(decodeSignedInteger('C')).toEqual(2);
+      expect(decodeSignedInteger(']')).toEqual(15);
+      expect(decodeSignedInteger('^')).toEqual(-16);
+
+      expect(decodeSignedInteger('_@')).toEqual(16);
+      expect(decodeSignedInteger('__@')).toEqual(16 * 32);
+      expect(decodeSignedInteger('___@')).toEqual(16 * 32 * 32);
+    });
+  });
+
   describe('encodeUnsignedInteger', function() {
     it('returns expected value', function() {
       var encodeUnsignedInteger = ol.parser.polyline.encodeUnsignedInteger;
@@ -36,6 +54,23 @@ describe('ol.parser.polyline', function() {
       expect(encodeUnsignedInteger(32 * 32 * 32)).toEqual('___@');
     });
   });
+
+  describe('decodeUnsignedInteger', function() {
+    it('returns expected value', function() {
+      var decodeUnsignedInteger = ol.parser.polyline.decodeUnsignedInteger;
+
+      expect(decodeUnsignedInteger('?')).toEqual(0);
+      expect(decodeUnsignedInteger('@')).toEqual(1);
+      expect(decodeUnsignedInteger('A')).toEqual(2);
+      expect(decodeUnsignedInteger(']')).toEqual(30);
+      expect(decodeUnsignedInteger('^')).toEqual(31);
+      expect(decodeUnsignedInteger('_@')).toEqual(32);
+
+      expect(decodeUnsignedInteger('__@')).toEqual(32 * 32);
+      expect(decodeUnsignedInteger('__D')).toEqual(5 * 32 * 32);
+      expect(decodeUnsignedInteger('___@')).toEqual(32 * 32 * 32);
+    });
+  });
 });
 
 goog.require('ol.parser.polyline');