add support for big endian

fixes #36

Author: Tony Crisci

lib/dbus-buffer.js

@@ -2,9 +2,10 @@ const {parseSignature} = require('./signature');
 const { getBigIntCompat } = require('./library-options');
 const JSBI = require('jsbi');
 const Long = require('long');
+const LE = require('./constants').endianness.le;
 
 // Buffer + position + global start position ( used in alignment )
-function DBusBuffer(buffer, startPos, options) {
+function DBusBuffer(buffer, startPos, endian, options) {
   if (typeof options !== 'object') {
     options = { ayBuffer: true };
   } else if (options.ayBuffer === undefined) {
@@ -13,6 +14,7 @@ function DBusBuffer(buffer, startPos, options) {
   }
   this.options = options;
   this.buffer = buffer;
+  this.endian = endian;
   (this.startPos = startPos ? startPos : 0), (this.pos = 0);
 }
 
@@ -29,35 +31,55 @@ DBusBuffer.prototype.readInt8 = function() {
 
 DBusBuffer.prototype.readSInt16 = function() {
   this.align(1);
-  var res = this.buffer.readInt16LE(this.pos);
+
+  var res = (this.endian === LE ?
+    this.buffer.readInt16LE(this.pos) :
+    this.buffer.readInt16BE(this.pos));
+
   this.pos += 2;
   return res;
 };
 
 DBusBuffer.prototype.readInt16 = function() {
   this.align(1);
-  var res = this.buffer.readUInt16LE(this.pos);
+
+  var res = (this.endian === LE ?
+    this.buffer.readUInt16LE(this.pos) :
+    this.buffer.readUInt16BE(this.pos));
+
   this.pos += 2;
   return res;
 };
 
 DBusBuffer.prototype.readSInt32 = function() {
   this.align(2);
-  var res = this.buffer.readInt32LE(this.pos);
+
+  var res = (this.endian === LE ?
+    this.buffer.readInt32LE(this.pos) :
+    this.buffer.readInt32BE(this.pos));
+
   this.pos += 4;
   return res;
 };
 
 DBusBuffer.prototype.readInt32 = function() {
   this.align(2);
-  var res = this.buffer.readUInt32LE(this.pos);
+
+  var res = (this.endian === LE ?
+    this.buffer.readUInt32LE(this.pos) :
+    this.buffer.readUInt32BE(this.pos));
+
   this.pos += 4;
   return res;
 };
 
 DBusBuffer.prototype.readDouble = function() {
   this.align(3);
-  var res = this.buffer.readDoubleLE(this.pos);
+
+  var res = (this.endian === LE ?
+    this.buffer.readDoubleLE(this.pos) :
+    this.buffer.readDoubleBE(this.pos));
+
   this.pos += 8;
   return res;
 };

lib/message.js

@@ -15,31 +15,39 @@ module.exports.unmarshalMessages = function messageParser(
   var fieldsLength, fieldsLengthPadded;
   var fieldsAndBodyLength = 0;
   var bodyLength = 0;
+  var endian = 0;
+  const LE = constants.endianness.le;
   stream.on('readable', function() {
     while (1) {
       if (state === 0) {
         header = stream.read(16);
-        if (!header) break;
+        if (!header) {
+          break;
+        }
         state = 1;
 
-        fieldsLength = header.readUInt32LE(12);
+        endian = header.readUInt8();
+
+        fieldsLength = (endian === LE ? header.readUInt32LE(12) : header.readUInt32BE(12));
         fieldsLengthPadded = ((fieldsLength + 7) >> 3) << 3;
-        bodyLength = header.readUInt32LE(4);
+        bodyLength = (endian === LE ? header.readUInt32LE(4) : header.readUInt32BE(4));
         fieldsAndBodyLength = fieldsLengthPadded + bodyLength;
       } else {
         fieldsAndBody = stream.read(fieldsAndBodyLength);
-        if (!fieldsAndBody) break;
+        if (!fieldsAndBody) {
+          break;
+        }
         state = 0;
 
-        var messageBuffer = new DBusBuffer(fieldsAndBody, undefined, opts);
+        var messageBuffer = new DBusBuffer(fieldsAndBody, 0, endian, opts);
         var unmarshalledHeader = messageBuffer.readArray(
           headerSignature[0].child[0],
           fieldsLength
         );
         messageBuffer.align(3);
         var headerName;
         var message = {};
-        message.serial = header.readUInt32LE(8);
+        message.serial = (endian === LE ? header.readUInt32LE(8) : header.readUInt32BE(8));
 
         for (var i = 0; i < unmarshalledHeader.length; ++i) {
           headerName = constants.headerTypeName[unmarshalledHeader[i][0]];
@@ -61,7 +69,8 @@ module.exports.unmarshalMessages = function messageParser(
 // given buffer which contains entire message deserialise it
 // TODO: factor out common code
 module.exports.unmarshall = function unmarshall(buff, opts) {
-  var msgBuf = new DBusBuffer(buff, undefined, opts);
+  var endian = buff.readUInt8();
+  var msgBuf = new DBusBuffer(buff, 0, endian, opts);
   var headers = msgBuf.read('yyyyuua(yv)');
   var message = {};
   for (var i = 0; i < headers[6].length; ++i) {