var_handle.cc

/* Copyright 2021 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.
==============================================================================*/

#include <stdint.h>
#include <string.h>

#include <string>
#include <utility>

#include "tensorflow/lite/core/c/builtin_op_data.h"
#include "tensorflow/lite/core/c/common.h"
#include "tensorflow/lite/core/subgraph.h"
#include "tensorflow/lite/experimental/resource/resource_variable.h"
#include "tensorflow/lite/kernels/internal/tensor.h"
#include "tensorflow/lite/kernels/kernel_util.h"

namespace tflite {
namespace ops {
namespace builtin {
namespace var_handle {
// Util struct with params that identifies the resource.
struct VarParams {
  int resource_id;
};

void* Init(TfLiteContext* context, const char* buffer, size_t length) {
  const auto* var_params =
      reinterpret_cast<const TfLiteVarHandleParams*>(buffer);
  VarParams* params = new VarParams;
  auto* subgraph = reinterpret_cast<Subgraph*>(context->impl_);
  // Create a new entry if doesn't exist, return the existing one otherwise.
  auto it = subgraph->resource_ids().insert(std::make_pair(
      std::make_pair(
          std::string(var_params->container ? var_params->container : ""),
          std::string(var_params->shared_name ? var_params->shared_name : "")),
      static_cast<int>(subgraph->resource_ids().size())));
  params->resource_id = it.first->second;
  return params;
}

void Free(TfLiteContext* context, void* buffer) {
  delete reinterpret_cast<VarParams*>(buffer);
}

TfLiteStatus Prepare(TfLiteContext* context, TfLiteNode* node) {
  TfLiteTensor* output;
  TF_LITE_ENSURE_OK(context, GetOutputSafe(context, node, 0, &output));

  output->allocation_type = kTfLiteArenaRwPersistent;
  const int kBytesRequired = sizeof(int32_t);
  TfLiteTensorRealloc(kBytesRequired, output);
  output->bytes = kBytesRequired;

  return kTfLiteOk;
}

TfLiteStatus Eval(TfLiteContext* context, TfLiteNode* node) {
  auto* op_data = static_cast<VarParams*>(node->user_data);
  TF_LITE_ENSURE(context, op_data != nullptr);

  TfLiteTensor* output;
  TF_LITE_ENSURE_OK(context, GetOutputSafe(context, node, 0, &output));

  memcpy(output->data.raw, reinterpret_cast<char*>(&op_data->resource_id),
         sizeof(op_data->resource_id));
  return kTfLiteOk;
}

}  // namespace var_handle

TfLiteRegistration* Register_VAR_HANDLE() {
  static TfLiteRegistration r = {var_handle::Init, var_handle::Free,
                                 var_handle::Prepare, var_handle::Eval};
  return &r;
}

}  // namespace builtin
}  // namespace ops
}  // namespace tflite