Use pad_id for padding in tensorflow op

tensorflow/sentencepiece_processor_ops.cc

@@ -141,6 +141,15 @@ class SentencePieceBaseOp : public OpKernel {
   }
 
  protected:
+  void GetPad(int32* pad) const { *pad = pad_id_; }
+
+  void GetPad(std::string* pad) const {
+    pad->clear();
+    if (sentencepiece_processor_ && pad_id_ >= 0 &&
+        pad_id_ != sentencepiece_processor_->unk_id())
+      *pad = sentencepiece_processor_->IdToPiece(pad_id_);
+  }
+
   std::shared_ptr<SentencePieceProcessor> sentencepiece_processor_;
   int bos_id_ = -1;
   int eos_id_ = -1;
@@ -378,7 +387,9 @@ template <typename T>
 class SentencePieceEncodeDenseOp : public SentencePieceEncodeOpBase<T> {
  public:
   explicit SentencePieceEncodeDenseOp(OpKernelConstruction* context)
-      : SentencePieceEncodeOpBase<T>(context) {}
+      : SentencePieceEncodeOpBase<T>(context) {
+    this->GetPad(&pad_);
+  }
 
   // protected:
   void MakeOutputTensor(OpKernelContext* context,
@@ -406,11 +417,14 @@ class SentencePieceEncodeDenseOp : public SentencePieceEncodeOpBase<T> {
     for (int row = 0; row < batch_size; ++row) {
       for (int col = 0; col < max_sequence_length; ++col) {
         values_tensor_output(row, col) =
-            col < pieces[row].size() ? pieces[row][col] : T();
+            col < pieces[row].size() ? pieces[row][col] : pad_;
       }
       length_tensor_output(row) = pieces[row].size();
     }
   }
+
+ private:
+  T pad_;
 };
 
 template <typename T>