code: function getDirEntryCount(app1Start, littleEndian) {
          var promise = new qq.Promise();
  
          qq.readBlobToHex(fileOrBlob, app1Start + 18, 2).then(function(hex) {
              if (littleEndian) {
                  return promise.success(parseLittleEndian(hex));
              }
              else {
                  promise.success(parseInt(hex, 16));
              }
          });
  
          return promise;
      }
docs: Determine the number of directory entries in the EXIF header.