Ensure support for little endian without 'Exif\0\0' prefix (#35)

index.js

@@ -2,7 +2,7 @@ var tags = require('./tags');
 
 module.exports = function (buffer) {
   var startingOffset = 0;
-  if (buffer.toString('ascii', 0, 3) !== 'MM\0' && buffer.toString('ascii', 0, 3) !== 'II\0') {
+  if (buffer.toString('ascii', 0, 3) !== 'MM\0' && buffer.toString('ascii', 0, 3) !== 'II\x2a') {
     startingOffset = 6;
     if (buffer.toString('ascii', 0, 5) !== 'Exif\0')
       throw new Error('Invalid EXIF data: buffer should start with "Exif", "MM" or "II".');

test/index.js

@@ -8,6 +8,7 @@ var tetons = fs.readFileSync(__dirname + '/data/tetons.exif');
 var IMG_0774 = fs.readFileSync(__dirname + '/data/IMG_0774.exif');
 var pngWithExif = fs.readFileSync(__dirname + '/data/png-exif.exif');
 var non_ascii = fs.readFileSync(__dirname + '/data/non-ascii.exif');
+var littleEndian = fs.readFileSync(__dirname + '/data/little-endian.exif');
 
 describe('exif-reader', function () {
   it('should read tiff and exif data', function () {
@@ -234,6 +235,29 @@ describe('exif-reader', function () {
     });
   });
 
+  it('should read little endian data', function () {
+    expect(exif(littleEndian), 'to equal', {
+      bigEndian: false,
+      Image: {
+        Orientation: 1,
+        XResolution: 25.4,
+        YResolution: 25.4,
+        ResolutionUnit: 2,
+        Software: 'sharp',
+        YCbCrPositioning: 1,
+        ExifTag: 120
+      },
+      Photo: {
+        ExifVersion: Buffer.from([0x30, 0x32, 0x31, 0x30]),
+        ComponentsConfiguration: Buffer.from([0x01, 0x02, 0x03, 0x00]),
+        FlashpixVersion: Buffer.from([0x30, 0x31, 0x30, 0x30]),
+        ColorSpace: 65535,
+        PixelXDimension: 1,
+        PixelYDimension: 1
+      }
+    });
+  });
+
   it('should error when missing Exif tag', function () {
     expect(function () {
       exif(Buffer.alloc(50));