fileMd5Service.md5-拒绝/解决承诺

Question

如何强制对fileMd5Service.md5 Promise进行拒绝/解决？对于大文件，此过程会花费一些时间，我需要处理用户取消操作。

    mvm.calcMd5 = fileMd5Service.md5(mvm.file)
    .progress(function(evt) {
      mvm.progressPercentage = parseInt(100.0 * evt.loaded / evt.total);
    })
    .error(function(error) {})
    .success(function(md5sum) {
      mvm.progressPercentage = 0;
      mvm.md5Checksum = ByteBuffer.fromHex(md5sum).toBase64();
      var data = {
        'contentType': 'application/octet-stream',
        'md5CheckSum': mvm.md5Checksum,
        fileName: mvm.file.name
      };
    });


  function cancelUpload() {
    console.log(mvm.calcMd5);
    mvm.calcMd5.resolve() // not an option
    $http.pendingRequests.forEach(function(request) {
                if (request.cancel) {
                    request.cancel.resolve();
                }
            });
    mvm.info = null;
  }