Program Listing for File codecs.hpp

            

            
/*
* SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
* SPDX-License-Identifier: Apache-2.0
*
* 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 HOLOSCAN_CORE_CODECS_HPP
#define HOLOSCAN_CORE_CODECS_HPP

#include <complex>
#include <cstdint>
#include <functional>
#include <memory>
#include <string>
#include <type_traits>
#include <typeindex>
#include <typeinfo>
#include <unordered_map>
#include <utility>
#include <vector>

#include "./common.hpp"
#include "./endpoint.hpp"
#include "./errors.hpp"
#include "./expected.hpp"
#include "./type_traits.hpp"

#include "gxf/core/expected.hpp"
#include "gxf/serialization/serialization_buffer.hpp"

// Note: Currently the GXF UCX extension transmits using little-endian byte order. All hardware
// supported by Holoscan SDK is also little endian. To support big endian platforms, we
// would need to update the codecs in this file to properly handle endianness.

namespace holoscan {

// codec template struct so users can define their own codec class
// i.e. following the design of yaml-cpp's YAML::convert
template <typename T>
struct codec;

// Codec type 1: trivial binary types (float, etc.)
//
// Types that can be serialized by writing binary data where the number
// of bytes to be written is based on sizeof(typeT).

template <typename typeT>
static inline expected<size_t, RuntimeError> serialize_trivial_type(const typeT& value,
                                                                    Endpoint* endpoint) {
  return endpoint->write_trivial_type(&value);
}

template <typename typeT>
static inline expected<typeT, RuntimeError> deserialize_trivial_type(Endpoint* endpoint) {
  typeT encoded;
  auto maybe_value = endpoint->read_trivial_type(&encoded);
  if (!maybe_value) { return forward_error(maybe_value); }
  return encoded;
}

// TODO: currently not handling integer types separately
template <typename typeT>
struct codec {
  static expected<size_t, RuntimeError> serialize(const typeT& value, Endpoint* endpoint) {
    return serialize_trivial_type<typeT>(value, endpoint);
  }
  static expected<typeT, RuntimeError> deserialize(Endpoint* endpoint) {
    return deserialize_trivial_type<typeT>(endpoint);
  }
};

// Codec type 3: basic container types
//
// For vectorT types storing multiple items contiguously in memory
// (e.g. std::vector, std::array, std::string).
//
// It requires that vectorT have methods size(), data(), and operator[]

#pragma pack(push, 1)
struct ContiguousDataHeader {
  size_t size;
  uint8_t bytes_per_element;
};
#pragma pack(pop)

template <typename vectorT>
static inline expected<size_t, RuntimeError> serialize_binary_blob(const vectorT& data,
                                                                   Endpoint* endpoint) {
  ContiguousDataHeader header;
  header.size = data.size();
  header.bytes_per_element = header.size > 0 ? sizeof(data[0]) : 1;
  auto size = endpoint->write_trivial_type<ContiguousDataHeader>(&header);
  if (!size) { return forward_error(size); }
  auto size2 = endpoint->write(data.data(), header.size * header.bytes_per_element);
  if (!size2) { return forward_error(size2); }
  return size.value() + size2.value();
}

template <typename vectorT>
static inline expected<vectorT, RuntimeError> deserialize_binary_blob(Endpoint* endpoint) {
  ContiguousDataHeader header;
  auto header_size = endpoint->read_trivial_type<ContiguousDataHeader>(&header);
  if (!header_size) { return forward_error(header_size); }
  vectorT data;
  data.resize(header.size);
  auto result = endpoint->read(data.data(), header.size * header.bytes_per_element);
  if (!result) { return forward_error(result); }
  return data;
}

// codec for vector of trivially serializable typeT
template <typename typeT>
struct codec<std::vector<typeT>> {
  static expected<size_t, RuntimeError> serialize(const std::vector<typeT>& value,
                                                  Endpoint* endpoint) {
    return serialize_binary_blob<std::vector<typeT>>(value, endpoint);
  }
  static expected<std::vector<typeT>, RuntimeError> deserialize(Endpoint* endpoint) {
    return deserialize_binary_blob<std::vector<typeT>>(endpoint);
  }
};

// codec for std::string
template <>
struct codec<std::string> {
  static expected<size_t, RuntimeError> serialize(const std::string& value, Endpoint* endpoint) {
    return serialize_binary_blob<std::string>(value, endpoint);
  }
  static expected<std::string, RuntimeError> deserialize(Endpoint* endpoint) {
    return deserialize_binary_blob<std::string>(endpoint);
  }
};

// Codec type 4: serialization of std::vector<bool> only
//
// Note: Have to serialize std::vector<bool> differently than the numeric types due to how it is
// packed. This is currently inefficient as 8x the data size is transferred due to bit->byte
// conversion. Could revisit packing the data more efficiently if needed, but likely not
// worth it if only a small length vector is being sent.

// codec of std::vector<bool>
template <>
struct codec<std::vector<bool>> {
  static expected<size_t, RuntimeError> serialize(const std::vector<bool>& data,
                                                  Endpoint* endpoint) {
    ContiguousDataHeader header;
    header.size = data.size();
    header.bytes_per_element = header.size > 0 ? sizeof(data[0]) : 1;
    auto size = endpoint->write_trivial_type<ContiguousDataHeader>(&header);
    if (!size) { return forward_error(size); }
    size_t total_bytes = size.value();
    expected<size_t, RuntimeError> size2;
    for (const auto b : data) {
      bool bool_b = b;
      size2 = endpoint->write_trivial_type<bool>(&bool_b);
      if (!size2) { return forward_error(size2); }
    }
    total_bytes += size2.value() * header.size;
    return total_bytes;
  }

  static expected<std::vector<bool>, RuntimeError> deserialize(Endpoint* endpoint) {
    ContiguousDataHeader header;
    auto header_size = endpoint->read_trivial_type<ContiguousDataHeader>(&header);
    if (!header_size) { return forward_error(header_size); }
    std::vector<bool> data;
    data.resize(header.size);
    expected<size_t, RuntimeError> result;
    for (auto&& b : data) {
      bool bool_b;
      result = endpoint->read_trivial_type<bool>(&bool_b);
      if (!result) { return forward_error(result); }
      b = bool_b;
    }
    return data;
  }
};

// Codec type 5: serialization of nested container types
// e.g. std::vector<std::vector<float>>, std::vector<std::string>
//

template <typename typeT>
static inline expected<size_t, RuntimeError> serialize_vector_of_vectors(const typeT& vectors,
                                                                         Endpoint* endpoint) {
  size_t total_size = 0;

  // header is just the total number of vectors
  size_t num_vectors = vectors.size();
  auto size = endpoint->write_trivial_type<size_t>(&num_vectors);
  if (!size) { return forward_error(size); }
  total_size += size.value();

  using vectorT = typename typeT::value_type;

  // now transmit each individual vector
  for (const auto& vector : vectors) {
    size = codec<vectorT>::serialize(vector, endpoint);
    if (!size) { return forward_error(size); }
    total_size += size.value();
  }
  return total_size;
}

template <typename typeT>
static inline expected<typeT, RuntimeError> deserialize_vector_of_vectors(Endpoint* endpoint) {
  size_t num_vectors;
  auto size = endpoint->read_trivial_type<size_t>(&num_vectors);
  if (!size) { return forward_error(size); }

  using vectorT = typename typeT::value_type;

  std::vector<vectorT> data;
  data.reserve(num_vectors);
  for (size_t i = 0; i < num_vectors; i++) {
    auto vec = codec<vectorT>::deserialize(endpoint);
    if (!vec) { return forward_error(vec); }
    data.push_back(vec.value());
  }
  return data;
}

template <typename typeT>
struct codec<std::vector<std::vector<typeT>>> {
  static expected<size_t, RuntimeError> serialize(const std::vector<std::vector<typeT>>& value,
                                                  Endpoint* endpoint) {
    return serialize_vector_of_vectors<std::vector<std::vector<typeT>>>(value, endpoint);
  }
  static expected<std::vector<std::vector<typeT>>, RuntimeError> deserialize(Endpoint* endpoint) {
    return deserialize_vector_of_vectors<std::vector<std::vector<typeT>>>(endpoint);
  }
};

template <>
struct codec<std::vector<std::string>> {
  static expected<size_t, RuntimeError> serialize(const std::vector<std::string>& value,
                                                  Endpoint* endpoint) {
    return serialize_vector_of_vectors<std::vector<std::string>>(value, endpoint);
  }
  static expected<std::vector<std::string>, RuntimeError> deserialize(Endpoint* endpoint) {
    return deserialize_vector_of_vectors<std::vector<std::string>>(endpoint);
  }
};

// codec for shared_ptr types
// Serializes the contents of the shared_ptr. On deserialize, a new shared_ptr to the deserialized
// value is returned.
template <typename typeT>
struct codec<std::shared_ptr<typeT>> {
  static expected<size_t, RuntimeError> serialize(std::shared_ptr<typeT> value,
                                                  Endpoint* endpoint) {
    return codec<typeT>::serialize(*value, endpoint);
  }
  static expected<std::shared_ptr<typeT>, RuntimeError> deserialize(Endpoint* endpoint) {
    auto value = codec<typeT>::deserialize(endpoint);
    if (!value) { return forward_error(value); }
    return std::make_shared<typeT>(value.value());
  }
};
}  // namespace holoscan

#endif/* HOLOSCAN_CORE_CODECS_HPP */