add index-mapping functionality

Author: Martin Schuhfuss

lib/ws281x-native.js

@@ -1,25 +1,96 @@
-// 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
-// test for matches the raspberry-pi before loading the native-module
-if(process.arch === 'arm' || process.platform === 'linux') {
-  var fs = require('fs');
+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
+    // test for matches the raspberry-pi before loading the native-module
+    if(process.arch === 'arm' || process.platform === 'linux') {
+        var fs = require('fs');
 
-  // we are doing stuff here that will only work on the Broadcom BCM
-  var isBCM2708 = (function() {
-    var cpuInfo = fs.readFileSync('/proc/cpuinfo').toString();
+        // will only work on the Broadcom BCM2708
+        var isBCM2708 = (function() {
+            var cpuInfo = fs.readFileSync('/proc/cpuinfo').toString();
 
-    return /hardware\s*:\s*bcm2708/i.test(cpuInfo);
-  } ());
+            return /hardware\s*:\s*bcm2708/i.test(cpuInfo);
+        } ());
 
-  if(isBCM2708) {
-    module.exports = require('./binding/rpi_ws281x.node');
+        if(isBCM2708) {
+            return require('./binding/rpi_ws281x.node');
+        }
+    }
 
-    return;
-  }
+    return null;
 }
 
-process.stderr.write(
-    '[rpi-ws281x-native] it looks like you are not running the module on a raspberry pi. ' +
-    'As it won\'t work and even might be dangerous, we stop it right here.\n'
-);
-process.exit(-1);
+
+var ws281xNative = getNativeBindings();
+if(!ws281xNative) {
+    process.stderr.write(
+        '[rpi-ws281x-native] it looks like you are not running the module ' +
+        'on a raspberry pi. Will only return stubs for native ' +
+        'interface-functions.\n'
+    );
+
+    ws281xNative = {
+        init: function() {},
+        render: function() {},
+        reset: function() {}
+    };
+}
+
+
+
+var _numLeds = 0,
+    _indexMapping = null;
+
+
+function remap(src, indexMapping) {
+    var dest = new Uint32Array(src.length);
+
+    for(var i=0; i<src.length; i++) {
+        dest[i] = src[indexMapping[i]];
+    }
+
+    return dest;
+}
+
+
+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);
+        }
+
+        ws281xNative.render(data);
+    },
+
+    /**
+     *
+     */
+    reset: function() {
+        ws281xNative.reset();
+    }
+};