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VariantAs.hpp
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VariantAs.hpp
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// ArduinoJson - arduinojson.org
// Copyright Benoit Blanchon 2014-2020
// MIT License
#pragma once
#include <ArduinoJson/Strings/IsWriteableString.hpp>
namespace ARDUINOJSON_NAMESPACE {
class ArrayRef;
class ArrayConstRef;
class ObjectRef;
class ObjectConstRef;
class VariantRef;
class VariantConstRef;
// A metafunction that returns the type of the value returned by
// VariantRef::as<T>()
template <typename T>
struct VariantAs {
typedef T type;
};
template <>
struct VariantAs<char*> {
typedef const char* type;
};
// A metafunction that returns the type of the value returned by
// VariantRef::as<T>()
template <typename T>
struct VariantConstAs {
typedef typename VariantAs<T>::type type;
};
template <>
struct VariantConstAs<VariantRef> {
typedef VariantConstRef type;
};
template <>
struct VariantConstAs<ObjectRef> {
typedef ObjectConstRef type;
};
template <>
struct VariantConstAs<ArrayRef> {
typedef ArrayConstRef type;
};
// ---
template <typename T>
inline typename enable_if<is_integral<T>::value, T>::type variantAs(
const VariantData* data) {
return data != 0 ? data->asIntegral<T>() : T(0);
}
template <typename T>
inline typename enable_if<is_enum<T>::value, T>::type variantAs(
const VariantData* data) {
return data != 0 ? static_cast<T>(data->asIntegral<int>()) : T();
}
template <typename T>
inline typename enable_if<is_same<T, bool>::value, T>::type variantAs(
const VariantData* data) {
return data != 0 ? data->asBoolean() : false;
}
template <typename T>
inline typename enable_if<is_floating_point<T>::value, T>::type variantAs(
const VariantData* data) {
return data != 0 ? data->asFloat<T>() : T(0);
}
template <typename T>
inline typename enable_if<is_same<T, const char*>::value ||
is_same<T, char*>::value,
const char*>::type
variantAs(const VariantData* data) {
return data != 0 ? data->asString() : 0;
}
template <typename T>
T variantAs(VariantData* data, MemoryPool*) {
// By default use the read-only conversion.
// There are specializations for
// - ArrayRef
return variantAs<T>(data);
}
template <typename T>
inline typename enable_if<is_same<ArrayConstRef, T>::value, T>::type variantAs(
const VariantData* data);
template <typename T>
inline typename enable_if<is_same<ObjectConstRef, T>::value, T>::type variantAs(
const VariantData* data);
template <typename T>
inline typename enable_if<is_same<VariantConstRef, T>::value, T>::type
variantAs(const VariantData* data);
template <typename T>
inline typename enable_if<IsWriteableString<T>::value, T>::type variantAs(
const VariantData* data);
} // namespace ARDUINOJSON_NAMESPACE