restructured module and implmented event-listener interface

Author: Martin Schuhfuss

lib/ws281x-native.js

@@ -1,3 +1,5 @@
+var EventEmitter = require('events').EventEmitter;
+
 function getNativeBindings() {
     // the native module might even be harmful (or won't work in the best case)
     // in the wrong environment, so we make sure that at least everything we can
@@ -21,6 +23,7 @@ function getNativeBindings() {
 }
 
 
+// fallback to empty stub-functions if not on RPi.
 var ws281xNative = getNativeBindings();
 if(!ws281xNative) {
     process.stderr.write(
@@ -53,44 +56,58 @@ function remap(src, indexMapping) {
 }
 
 
-module.exports = {
-    /**
-     *
-     * @param numLeds
-     * @param options
-     */
-    init: function(numLeds, options) {
-        _numLeds = numLeds;
-
-        ws281xNative.init(numLeds, options);
-    },
-
-    /**
-     * registers an index-mapping.
-     * Index: destination-index, Value: Source-Index
-     *
-     * @param {Array.<Number>} mapping
-     */
-    setIndexMapping: function(mapping) {
-        _indexMapping = mapping;
-    },
-
-    /**
-     *
-     * @param data
-     */
-    render: function(data) {
-        if(_indexMapping) {
-            data = remap(data, _indexMapping);
-        }
+var ws281x = new EventEmitter();
+
+/**
+ * configures PWM and DMA for sending data to the LEDs
+ *
+ * @param {Number} numLeds  number of LEDs to be controlled
+ * @param {?Object} options  (acutally only tested with default-values)
+ *                           intialization-options for the library
+ *                           (PWM frequency, DMA channel, GPIO, Brightness)
+ */
+ws281x.init = function(numLeds, options) {
+    _numLeds = numLeds;
 
-        ws281xNative.render(data);
-    },
+    ws281xNative.init(numLeds, options);
+};
+
+/**
+ * register a mapping to manipulate array-indices within the
+ * data-array before rendering.
+ *
+ * @param {Array.<Number>} map  the mapping, indexed by destination.
+ */
+ws281x.setIndexMapping = function(mapping) {
+    _indexMapping = mapping;
+};
 
-    /**
-     *
-     */
-    reset: function() {
-        ws281xNative.reset();
+/**
+ * send data to the LED-strip.
+ *
+ * @param {Uint32Array} data  the pixel-data, 24bit per pixel in
+ *                            RGB-format (0xff0000 is red).
+ * @return {Uint32Array} data as it was sent to the LED-strip
+ */
+ws281x.render = function(data) {
+    this.emit('beforeRender', data);
+
+    if(_indexMapping) {
+        data = remap(data, _indexMapping);
     }
+
+    ws281xNative.render(data);
+    this.emit('render', data);
+
+    return data;
 };
+
+/**
+ * clears all LEDs, resets the PWM and DMA-parts and deallocates
+ * all internal structures.
+ */
+ws281x.reset = function() {
+    ws281xNative.reset();
+};
+
+module.exports = ws281x;