Added promise support

lib/index.js

@@ -2,6 +2,30 @@ var Magic = require('../build/Release/magic');
 var fbpath = require('path').join(__dirname, '..', 'magic', 'magic');
 Magic.setFallback(fbpath);
 
+Magic.Magic.prototype.detectFileAsync = function(path) {
+  return new Promise((resolve, reject) => {
+    this.detectFile(path, (err, result) => {
+      if (err) {
+        return reject(err)
+      }
+
+      resolve(result)
+    })
+  })
+}
+
+Magic.Magic.prototype.detectAsync = function(buffer) {
+  return new Promise((resolve, reject) => {
+    this.detect(buffer, (err, mimeType) => {
+      if (err) {
+        return reject(err)
+      }
+
+      resolve(mimeType)
+    })
+  })
+}
+
 module.exports = {
   Magic: Magic.Magic,
   MAGIC_NONE: 0x000000, /* No flags (default for Windows) */

test/test.js

@@ -98,6 +98,32 @@ var tests = [
     },
     what: 'detect - Normal operation, mime type'
   },
+  { run: function() {
+      var magic = new mmm.Magic(mmm.MAGIC_MIME_TYPE);
+      magic.detectFileAsync(path.join(__dirname, '..', 'src', 'binding.cc'))
+        .then(result => {
+          assert.strictEqual(result, 'text/x-c++');
+          next();
+        });
+    },
+    what: 'detectFileAsync - Normal operation'
+  },
+  { run: function() {
+      var magic = new mmm.Magic(mmm.MAGIC_MIME_TYPE);
+      assert.rejects(magic.detectFileAsync('/no/such/path1234567')).then(next);
+    },
+    what: 'detectFileAsync - Error'
+  },
+  { run: function() {
+      var buf = fs.readFileSync(path.join(__dirname, '..', 'src', 'binding.cc'));
+      var magic = new mmm.Magic(mmm.MAGIC_MIME_TYPE);
+      magic.detectAsync(buf).then(result => {
+          assert.strictEqual(result, 'text/x-c++');
+          next();
+        });
+    },
+    what: 'detectAsync - Normal operation'
+  }
 ];
 
 function next() {