text: /**
   * Copyright 2019 Huawei Technologies Co., Ltd
   *
   * 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.
   */
  #ifndef DATASET_ENGINE_DATASETOPS_SOURCE_SAMPLER_SUBSET_RANDOM_SAMPLER_H_
  #define DATASET_ENGINE_DATASETOPS_SOURCE_SAMPLER_SUBSET_RANDOM_SAMPLER_H_
  
  #include <limits>
  #include <memory>
  #include <vector>
  
  #include "dataset/engine/datasetops/source/sampler/sampler.h"
  
  namespace mindspore {
  namespace dataset {
  // Randomly samples elements from a given list of indices, without replacement.
  class SubsetRandomSampler : public Sampler {
   public:
    // Constructor.
    // @param num_samples The number of samples to draw. 0 for the full amount.
    // @param indices List of indices from where we will randomly draw samples.
    // @param samples_per_buffer The number of ids we draw on each call to GetNextBuffer().
    // When samplesPerBuffer=0, GetNextBuffer() will draw all the sample ids and return them at once.
    explicit SubsetRandomSampler(int64_t num_samples, const std::vector<int64_t> &indices,
                                 std::int64_t samples_per_buffer = std::numeric_limits<int64_t>::max());
  
    // Destructor.
    ~SubsetRandomSampler() = default;
  
    // Initialize the sampler.
    // @return Status
    Status InitSampler() override;
  
    // Reset the internal variable to the initial state and reshuffle the indices.
    // @return Status
    Status Reset() override;
  
    // Get the sample ids.
    // @param[out] out_buffer The address of a unique_ptr to DataBuffer where the sample ids will be placed.
    // @note the sample ids (int64_t) will be placed in one Tensor and be placed into pBuffer.
    Status GetNextBuffer(std::unique_ptr<DataBuffer> *out_buffer) override;
  
   private:
    // A list of indices (already randomized in constructor).
    std::vector<int64_t> indices_;
  
    // Current sample id.
    int64_t sample_id_;
  
    // Current buffer id.
    int64_t buffer_id_;
  
    // A random number generator.
    std::mt19937 rand_gen_;
  };
  }  // namespace dataset
  }  // namespace mindspore
  
  #endif  // DATASET_ENGINE_DATASETOPS_SOURCE_SAMPLER_SUBSET_RANDOM_SAMPLER_H_
  