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+/* Copyright 2017 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+// Util methods to read and write String tensors.
+// String tensors are considered to be char tensor with protocol.
+//   [0, 3] 4 bytes: N, num of strings in the tensor in little endian.
+//   [(i+1)*4, (i+1)*4+3] 4 bytes: offset of i-th string in little endian.
+//   [(N+2)*4, (N+2)*4+3] 4 bytes: length of the whole char buffer.
+//   [offset(i), offset(i+1) - 1] : content of i-th string.
+// Example of a string tensor:
+// [
+//   2, 0, 0, 0,     # 2 strings.
+//   16, 0, 0, 0,    # 0-th string starts from index 12.
+//   18, 0, 0, 0,    # 1-st string starts from index 18.
+//   18, 0, 0, 0,    # total length of array.
+//   'A', 'B',       # 0-th string [16..17]: "AB"
+// ]                 # 1-th string, empty
+//
+// A typical usage:
+// In op.Eval(context, node):
+//   DynamicBuffer buf;
+//   # Add string "AB" to tensor, string is stored in dynamic buffer.
+//   buf.AddString("AB", 2);
+//   # Write content of DynamicBuffer to tensor in format of string tensor
+//   # described above.
+//   buf.WriteToTensor(tensor)
+
+#ifndef THIRD_PARTY_TENSORFLOW_CONTRIB_LITE_STRING_UTIL_H_
+#define THIRD_PARTY_TENSORFLOW_CONTRIB_LITE_STRING_UTIL_H_
+
+#include <vector>
+
+#include "tensorflow/contrib/lite/context.h"
+#include "tensorflow/contrib/lite/string.h"
+
+namespace tflite {
+
+// Convenient structure to store string pointer and length.
+typedef struct {
+  char* str;
+  int len;
+} StringRef;
+
+// DynamicBuffer holds temporary buffer that will be used to create a dynamic
+// tensor. A typical usage is to initialize a DynamicBuffer object, fill in
+// content and call CreateStringTensor in op.Eval().
+class DynamicBuffer {
+ public:
+  DynamicBuffer() : offset_({0}) {}
+
+  // Add string to dynamic buffer by resizing the buffer and copying the data.
+  void AddString(const StringRef& string);
+
+  // Add string to dynamic buffer by resizing the buffer and copying the data.
+  void AddString(const char* str, size_t len);
+
+  // Join a list of string with separator, and add as a single string to the
+  // buffer.
+  void AddJoinedString(const std::vector<StringRef>& strings, char separator);
+
+  // Fill content into a string tensor.
+  void WriteToTensor(TfLiteTensor* tensor);
+
+ private:
+  // Data buffer to store contents of strings, not including headers.
+  std::vector<char> data_;
+  // Offset of the starting index of each string in data buffer.
+  std::vector<int32_t> offset_;
+};
+
+// Return num of strings in a String tensor.
+int GetStringCount(const TfLiteTensor* tensor);
+
+// Get String pointer and length of index-th string in tensor.
+// NOTE: This will not create a copy of string data.
+StringRef GetString(const TfLiteTensor* tensor, int string_index);
+}  // namespace tflite
+
+#endif  // THIRD_PARTY_TENSORFLOW_CONTRIB_LITE_STRING_UTIL_H_