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558 lines
12 KiB
C++
558 lines
12 KiB
C++
//
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// Any.h
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//
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// Library: Foundation
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// Package: Core
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// Module: Any
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//
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// Copyright Kevlin Henney, 2000, 2001, 2002. All rights reserved.
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// Extracted from Boost 1.33.1 lib and adapted for poco: Peter Schojer/AppliedInformatics 2006-02-02
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Foundation_Any_INCLUDED
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#define Foundation_Any_INCLUDED
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#include "Poco/Exception.h"
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#include "Poco/MetaProgramming.h"
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#include <algorithm>
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#include <typeinfo>
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#include <cstring>
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#include <cstddef>
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#define poco_any_assert(cond) do { if (!(cond)) std::abort(); } while (0)
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namespace Poco {
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class Any;
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namespace Dynamic {
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class Var;
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class VarHolder;
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template <class T> class VarHolderImpl;
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}
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template <class T, std::size_t S>
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struct TypeSizeLE:
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std::integral_constant<bool, (sizeof(T) <= S)>{};
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template <class T, std::size_t S>
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struct TypeSizeGT:
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std::integral_constant<bool, (sizeof(T) > S)>{};
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template <typename PlaceholderT, unsigned int SizeV = POCO_SMALL_OBJECT_SIZE>
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union Placeholder
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/// ValueHolder union (used by Poco::Any and Poco::Dynamic::Var for small
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/// object optimization, when enabled).
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///
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/// If Holder<Type> fits into POCO_SMALL_OBJECT_SIZE bytes of storage,
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/// it will be placement-new-allocated into the local buffer
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/// (i.e. there will be no heap-allocation). The local buffer size is one byte
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/// larger - [POCO_SMALL_OBJECT_SIZE + 1], additional byte value indicating
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/// where the object was allocated (0 => heap, 1 => local).
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///
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/// Important: for SOO builds, only same-type (or trivial both-empty no-op)
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/// swap operation is allowed.
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{
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public:
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struct Size
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{
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enum { value = SizeV };
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};
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Placeholder(const Placeholder&) = delete;
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Placeholder(Placeholder&&) = delete;
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Placeholder& operator=(const Placeholder&) = delete;
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Placeholder& operator=(Placeholder&&) = delete;
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#ifndef POCO_NO_SOO
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Placeholder(): pHolder(0)
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{
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std::memset(holder, 0, sizeof(Placeholder));
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}
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~Placeholder()
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{
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destruct(false);
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}
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void swap(Placeholder& other) noexcept
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{
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if (!isEmpty() || !other.isEmpty())
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std::swap(holder, other.holder);
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}
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void erase()
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{
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destruct(true);
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}
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bool isEmpty() const
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{
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static char buf[SizeV+1] = {};
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return 0 == std::memcmp(holder, buf, SizeV+1);
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}
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bool isLocal() const
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{
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return holder[SizeV] != 0;
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}
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template<typename T, typename V,
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typename std::enable_if<TypeSizeLE<T, Placeholder::Size::value>::value>::type* = nullptr>
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PlaceholderT* assign(const V& value)
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{
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erase();
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new (reinterpret_cast<PlaceholderT*>(holder)) T(value);
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setLocal(true);
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return reinterpret_cast<PlaceholderT*>(holder);
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}
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template<typename T, typename V,
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typename std::enable_if<TypeSizeGT<T, Placeholder::Size::value>::value>::type* = nullptr>
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PlaceholderT* assign(const V& value)
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{
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erase();
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pHolder = new T(value);
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setLocal(false);
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return pHolder;
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}
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PlaceholderT* content() const
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{
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if (isLocal())
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return reinterpret_cast<PlaceholderT*>(holder);
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else
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return pHolder;
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}
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private:
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typedef std::max_align_t AlignerType;
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static_assert(sizeof(AlignerType) <= SizeV + 1, "Aligner type is bigger than the actual storage, so SizeV should be made bigger otherwise you simply waste unused memory.");
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void setLocal(bool local) const
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{
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holder[SizeV] = local ? 1 : 0;
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}
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void destruct(bool clear)
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{
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if (!isEmpty())
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{
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if (!isLocal())
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delete pHolder;
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else
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reinterpret_cast<PlaceholderT*>(holder)->~PlaceholderT();
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if (clear) std::memset(holder, 0, sizeof(Placeholder));
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}
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}
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mutable unsigned char holder[SizeV+1];
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AlignerType aligner;
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#else // POCO_NO_SOO
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Placeholder(): pHolder(0)
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{
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}
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~Placeholder()
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{
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delete pHolder;
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}
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void swap(Placeholder& other) noexcept
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{
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std::swap(pHolder, other.pHolder);
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}
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void erase()
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{
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delete pHolder;
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pHolder = 0;
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}
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bool isEmpty() const
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{
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return 0 == pHolder;
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}
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bool isLocal() const
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{
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return false;
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}
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template <typename T, typename V>
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PlaceholderT* assign(const V& value)
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{
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erase();
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return pHolder = new T(value);
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}
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PlaceholderT* content() const
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{
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return pHolder;
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}
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private:
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#endif // POCO_NO_SOO
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PlaceholderT* pHolder;
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};
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class Any
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/// Any class represents a general type and is capable of storing any type, supporting type-safe extraction
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/// of the internally stored data.
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///
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/// Code taken from the Boost 1.33.1 library. Original copyright by Kevlin Henney. Modified for Poco
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/// by Applied Informatics.
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///
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/// Modified for small object optimization support (optionally supported through conditional compilation)
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/// by Alex Fabijanic.
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{
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public:
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Any()
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/// Creates an empty any type.
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{
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}
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template<typename ValueType>
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Any(const ValueType & value)
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/// Creates an any which stores the init parameter inside.
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///
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/// Example:
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/// Any a(13);
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/// Any a(string("12345"));
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{
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construct(value);
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}
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Any(const Any& other)
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/// Copy constructor, works with both empty and initialized Any values.
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{
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if ((this != &other) && !other.empty())
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construct(other);
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}
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~Any()
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/// Destructor. If Any is locally held, calls ValueHolder destructor;
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/// otherwise, deletes the placeholder from the heap.
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{
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}
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Any& swap(Any& other) noexcept
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/// Swaps the content of the two Anys.
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///
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/// If an exception occurs during swapping, the program
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/// execution is aborted.
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{
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if (this == &other) return *this;
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if (!_valueHolder.isLocal() && !other._valueHolder.isLocal())
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{
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_valueHolder.swap(other._valueHolder);
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}
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else
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{
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try
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{
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Any tmp(*this);
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construct(other);
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other = tmp;
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}
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catch (...)
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{
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std::abort();
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}
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}
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return *this;
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}
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template<typename ValueType>
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Any& operator = (const ValueType& rhs)
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/// Assignment operator for all types != Any.
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///
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/// Example:
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/// Any a = 13;
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/// Any a = string("12345");
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{
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construct(rhs);
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return *this;
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}
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Any& operator = (const Any& rhs)
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/// Assignment operator for Any.
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{
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if ((this != &rhs) && !rhs.empty())
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construct(rhs);
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else if ((this != &rhs) && rhs.empty())
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_valueHolder.erase();
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return *this;
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}
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bool empty() const
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/// Returns true if the Any is empty.
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{
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return _valueHolder.isEmpty();
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}
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const std::type_info& type() const
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/// Returns the type information of the stored content.
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/// If the Any is empty typeid(void) is returned.
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/// It is recommended to always query an Any for its type info before
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/// trying to extract data via an AnyCast/RefAnyCast.
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{
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return empty() ? typeid(void) : content()->type();
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}
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bool local() const
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/// Returns true if data is held locally (ie. not allocated on the heap).
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/// If POCO_NO_SOO is defined, it always return false.
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/// The main purpose of this function is use for testing.
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{
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return _valueHolder.isLocal();
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}
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private:
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class ValueHolder
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{
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public:
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virtual ~ValueHolder() = default;
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virtual const std::type_info & type() const = 0;
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virtual void clone(Placeholder<ValueHolder>*) const = 0;
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};
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template<typename ValueType>
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class Holder : public ValueHolder
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{
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public:
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Holder(const ValueType & value) : _held(value)
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{
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}
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virtual const std::type_info& type() const
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{
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return typeid(ValueType);
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}
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virtual void clone(Placeholder<ValueHolder>* pPlaceholder) const
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{
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pPlaceholder->assign<Holder<ValueType>, ValueType>(_held);
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}
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ValueType _held;
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private:
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Holder & operator = (const Holder &);
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};
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ValueHolder* content() const
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{
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return _valueHolder.content();
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}
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template<typename ValueType>
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void construct(const ValueType& value)
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{
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_valueHolder.assign<Holder<ValueType>, ValueType>(value);
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}
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void construct(const Any& other)
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{
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if (!other.empty())
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other.content()->clone(&_valueHolder);
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else
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_valueHolder.erase();
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}
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Placeholder<ValueHolder> _valueHolder;
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template <typename ValueType>
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friend ValueType* AnyCast(Any*);
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template <typename ValueType>
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friend ValueType* UnsafeAnyCast(Any*);
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template <typename ValueType>
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friend const ValueType& RefAnyCast(const Any&);
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template <typename ValueType>
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friend ValueType& RefAnyCast(Any&);
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template <typename ValueType>
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friend ValueType AnyCast(Any&);
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};
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template <typename ValueType>
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ValueType* AnyCast(Any* operand)
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/// AnyCast operator used to extract the ValueType from an Any*. Will return a pointer
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/// to the stored value.
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///
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/// Example Usage:
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/// MyType* pTmp = AnyCast<MyType*>(pAny).
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/// Will return NULL if the cast fails, i.e. types don't match.
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{
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return operand && operand->type() == typeid(ValueType)
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? &static_cast<Any::Holder<ValueType>*>(operand->content())->_held
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: 0;
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}
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template <typename ValueType>
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const ValueType* AnyCast(const Any* operand)
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/// AnyCast operator used to extract a const ValueType pointer from an const Any*. Will return a const pointer
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/// to the stored value.
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///
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/// Example Usage:
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/// const MyType* pTmp = AnyCast<MyType*>(pAny).
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/// Will return NULL if the cast fails, i.e. types don't match.
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{
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return AnyCast<ValueType>(const_cast<Any*>(operand));
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}
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template <typename ValueType>
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ValueType AnyCast(Any& operand)
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/// AnyCast operator used to extract a copy of the ValueType from an Any&.
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///
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/// Example Usage:
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/// MyType tmp = AnyCast<MyType>(anAny).
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/// Will throw a BadCastException if the cast fails.
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/// Do not use an AnyCast in combination with references, i.e. MyType& tmp = ... or const MyType& tmp = ...
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/// Some compilers will accept this code although a copy is returned. Use the RefAnyCast in
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/// these cases.
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{
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typedef typename TypeWrapper<ValueType>::TYPE NonRef;
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NonRef* result = AnyCast<NonRef>(&operand);
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if (!result)
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{
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std::string s = "RefAnyCast: Failed to convert between Any types ";
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if (operand.content())
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{
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s.append(1, '(');
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s.append(operand.content()->type().name());
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s.append(" => ");
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s.append(typeid(ValueType).name());
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s.append(1, ')');
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}
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throw BadCastException(s);
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}
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return *result;
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}
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template <typename ValueType>
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ValueType AnyCast(const Any& operand)
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/// AnyCast operator used to extract a copy of the ValueType from an const Any&.
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///
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/// Example Usage:
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/// MyType tmp = AnyCast<MyType>(anAny).
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/// Will throw a BadCastException if the cast fails.
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/// Do not use an AnyCast in combination with references, i.e. MyType& tmp = ... or const MyType& = ...
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/// Some compilers will accept this code although a copy is returned. Use the RefAnyCast in
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/// these cases.
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{
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typedef typename TypeWrapper<ValueType>::TYPE NonRef;
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return AnyCast<NonRef&>(const_cast<Any&>(operand));
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}
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template <typename ValueType>
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const ValueType& RefAnyCast(const Any & operand)
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/// AnyCast operator used to return a const reference to the internal data.
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///
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/// Example Usage:
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/// const MyType& tmp = RefAnyCast<MyType>(anAny);
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{
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ValueType* result = AnyCast<ValueType>(const_cast<Any*>(&operand));
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if (!result)
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{
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std::string s = "RefAnyCast: Failed to convert between Any types ";
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if (operand.content())
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{
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s.append(1, '(');
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s.append(operand.content()->type().name());
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s.append(" => ");
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s.append(typeid(ValueType).name());
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s.append(1, ')');
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}
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throw BadCastException(s);
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}
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return *result;
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}
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template <typename ValueType>
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ValueType& RefAnyCast(Any& operand)
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/// AnyCast operator used to return a reference to the internal data.
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///
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/// Example Usage:
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/// MyType& tmp = RefAnyCast<MyType>(anAny);
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{
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ValueType* result = AnyCast<ValueType>(&operand);
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if (!result)
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{
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std::string s = "RefAnyCast: Failed to convert between Any types ";
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if (operand.content())
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{
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s.append(1, '(');
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s.append(operand.content()->type().name());
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s.append(" => ");
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s.append(typeid(ValueType).name());
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s.append(1, ')');
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}
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throw BadCastException(s);
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}
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return *result;
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}
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template <typename ValueType>
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ValueType* UnsafeAnyCast(Any* operand)
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/// The "unsafe" versions of AnyCast are not part of the
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/// public interface and may be removed at any time. They are
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/// required where we know what type is stored in the any and can't
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/// use typeid() comparison, e.g., when our types may travel across
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/// different shared libraries.
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{
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return &static_cast<Any::Holder<ValueType>*>(operand->content())->_held;
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}
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template <typename ValueType>
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const ValueType* UnsafeAnyCast(const Any* operand)
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/// The "unsafe" versions of AnyCast are not part of the
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/// public interface and may be removed at any time. They are
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/// required where we know what type is stored in the any and can't
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/// use typeid() comparison, e.g., when our types may travel across
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/// different shared libraries.
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{
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return AnyCast<ValueType>(const_cast<Any*>(operand));
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}
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} // namespace Poco
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#endif
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