cc/proto/util.h

//
// Copyright 2019 Google LLC
//
// 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 DIFFERENTIAL_PRIVACY_PROTO_UTIL_H_
#define DIFFERENTIAL_PRIVACY_PROTO_UTIL_H_

#include <limits>

#include "proto/confidence-interval.pb.h"
#include "proto/data.pb.h"

namespace differential_privacy {

template <typename T>
struct is_string
    : public std::integral_constant<
          bool,
          std::is_same<char*, typename std::decay<T>::type>::value ||
              std::is_same<const char*, typename std::decay<T>::type>::value ||
              std::is_same<std::string, typename std::decay<T>::type>::value> {
};
template <>
struct is_string<std::string> : std::true_type {};

template <typename T,
          typename std::enable_if<is_string<T>::value>::type* = nullptr>
T GetValue(const ValueType& value_type) {
  return value_type.string_value();
}

template <typename T,
          typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
T GetValue(const ValueType& value_type) {
  return value_type.int_value();
}

template <typename T, typename std::enable_if<
                          std::is_floating_point<T>::value>::type* = nullptr>
T GetValue(const ValueType& value_type) {
  return value_type.float_value();
}

template <typename T,
          typename std::enable_if<is_string<T>::value>::type* = nullptr>
void SetValue(ValueType* value_type, T value) {
  value_type->set_string_value(value);
}

template <typename T,
          typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
void SetValue(ValueType* value_type, T value) {
  value_type->set_int_value(value);
}

template <typename T, typename std::enable_if<
                          std::is_floating_point<T>::value>::type* = nullptr>
void SetValue(ValueType* value_type, T value) {
  value_type->set_float_value(value);
}

template <typename T>
ValueType MakeValueType(T value) {
  ValueType value_type;
  SetValue(&value_type, value);
  return value_type;
}

template <typename T,
          typename std::enable_if<is_string<T>::value>::type* = nullptr>
T GetValue(const Output& output, int64_t index = 0) {
  return output.elements(index).value().string_value();
}

template <typename T,
          typename std::enable_if<std::is_integral<T>::value>::type* = nullptr>
T GetValue(const Output& output, int64_t index = 0) {
  return output.elements(index).value().int_value();
}

template <typename T, typename std::enable_if<
                          std::is_floating_point<T>::value>::type* = nullptr>
T GetValue(const Output& output, int64_t index = 0) {
  return output.elements(index).value().float_value();
}

inline ConfidenceInterval GetNoiseConfidenceInterval(const Output& output,
                                                     int64_t index = 0) {
  return output.elements(index).noise_confidence_interval();
}

template <typename T>
Output MakeOutput(const T& value) {
  Output i;
  AddToOutput(&i, value);
  return i;
}

template <typename T>
Output MakeOutput(const T& value,
                  const ConfidenceInterval& noise_confidence_interval) {
  Output i;
  AddToOutput(&i, value, noise_confidence_interval);
  // Although the ErrorReport.noise_confidence_interval is deprecated, we still
  // keep it updated for a more seamless transition for existing clients. After
  // some time, we should no longer use ErrorReport.noise_confidence_interval.
  *(i.mutable_error_report()->mutable_noise_confidence_interval()) =
      noise_confidence_interval;
  return i;
}

template <typename T>
void AddToOutput(Output* output, const T& value) {
  Output_Element* element = output->add_elements();
  SetValue(element->mutable_value(), value);
}

template <typename T>
void AddToOutput(Output* output, const T& value,
                 const ConfidenceInterval& noise_confidence_interval) {
  Output_Element* element = output->add_elements();
  SetValue(element->mutable_value(), value);
  // Use the copy constructor here since operator= (or CopyFrom) would use an
  // uninitialized value, perhaps as ConfidenceInterval is a proto3 message
  // inside a proto2 message.
  ConfidenceInterval* ci_copy =
      new ConfidenceInterval(noise_confidence_interval);
  // Transfers ownership of ci_copy to element.
  element->set_allocated_noise_confidence_interval(ci_copy);
}

}  // namespace differential_privacy
#endif  // DIFFERENTIAL_PRIVACY_PROTO_UTIL_H_