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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
#pragma once
#include <QtGlobal>
#include <algorithm>
#include <cstdint>
#include <cstring>
#include <memory>
#include <type_traits>
namespace Utils {
namespace Internal {
using size_type = std::size_t;
template <uint MaximumShortStringDataAreaSize,
typename ControlType = typename std::conditional_t<(MaximumShortStringDataAreaSize < 64), uint8_t, uint16_t>>
struct ControlBlock
{
using SizeType = ControlType;
constexpr ControlBlock() noexcept = default;
constexpr ControlBlock(size_type shortStringSize,
bool isReadOnlyReference,
bool isReference) noexcept
: m_shortStringSize(static_cast<SizeType>(shortStringSize))
, m_isReadOnlyReference(isReadOnlyReference)
, m_isReference(isReference)
{}
constexpr void setShortStringSize(size_type size)
{
m_shortStringSize = static_cast<SizeType>(size);
}
constexpr size_type shortStringSize() const { return m_shortStringSize; }
constexpr void setIsReadOnlyReference(bool isReadOnlyReference)
{
m_isReadOnlyReference = isReadOnlyReference;
}
constexpr void setIsReference(bool isReference) { m_isReference = isReference; }
constexpr void setIsShortString(bool isShortString) { m_isReference = !isShortString; }
constexpr
SizeType stringSize() const
{
return m_shortStringSize;
}
constexpr
bool isReadOnlyReference() const
{
return m_isReadOnlyReference;
}
constexpr
bool isReference() const
{
return m_isReference;
}
constexpr
bool isShortString() const
{
return !m_isReference;
}
private:
ControlType m_shortStringSize : (sizeof(ControlType) * 8) - 2;
ControlType m_isReadOnlyReference : 1;
ControlType m_isReference : 1;
};
struct ReferenceLayout
{ union {
const char *constPointer;
char *pointer;
};
size_type size;
size_type capacity;
};
template<uint MaximumShortStringDataAreaSize, typename = void>
struct alignas(16) StringDataLayout
{
static_assert(MaximumShortStringDataAreaSize >= 15, "Size must be greater equal than 15 bytes!");
static_assert(MaximumShortStringDataAreaSize < 32, "Size must be less than 32 bytes!");
static_assert(((MaximumShortStringDataAreaSize + 1) % 16) == 0,
"Size + 1 must be dividable by 16 if under 64 and Size + 2 must be dividable by "
"16 if over 64!");
StringDataLayout() noexcept { reset(); }
constexpr StringDataLayout(const char *string, size_type size) noexcept
: control{0, true, true}
, reference{{string}, size, 0}
{}
template<size_type Size>
constexpr StringDataLayout(const char (&string)[Size]) noexcept
{
if constexpr (Size + 1 <= MaximumShortStringDataAreaSize) {
control = {Size - 1, false, false};
for (size_type i = 0; i < Size; ++i)
shortString[i] = string[i];
} else {
control = {0, true, true};
reference = {string, Size - 1, 0};
}
}
constexpr static size_type shortStringCapacity() noexcept
{
return MaximumShortStringDataAreaSize;
}
constexpr void reset() { control = ControlBlock<MaximumShortStringDataAreaSize>(); }
#pragma pack(push)
#pragma pack(1)
ControlBlock<MaximumShortStringDataAreaSize> control;
union {
char shortString[MaximumShortStringDataAreaSize];
struct
{
char dummy[sizeof(void *) - sizeof(ControlBlock<MaximumShortStringDataAreaSize>)];
ReferenceLayout reference;
};
};
#pragma pack(pop)
};
template<uint MaximumShortStringDataAreaSize>
struct alignas(16) StringDataLayout<MaximumShortStringDataAreaSize,
std::enable_if_t<MaximumShortStringDataAreaSize >= 32>>
{
static_assert(MaximumShortStringDataAreaSize > 31, "Size must be greater than 31 bytes!");
static_assert(MaximumShortStringDataAreaSize < 64
? ((MaximumShortStringDataAreaSize + 1) % 16) == 0
: ((MaximumShortStringDataAreaSize + 2) % 16) == 0,
"Size + 1 must be dividable by 16 if under 64 and Size + 2 must be dividable by "
"16 if over 64!");
StringDataLayout() noexcept { reset(); }
constexpr StringDataLayout(const char *string, size_type size) noexcept
: control{0, true, true}
, reference{{string}, size, 0}
{}
template<size_type Size>
constexpr StringDataLayout(const char (&string)[Size]) noexcept
{
if constexpr (Size + 1 <= MaximumShortStringDataAreaSize) {
control = {Size - 1, false, false};
for (size_type i = 0; i < Size; ++i)
shortString[i] = string[i];
} else {
control = {0, true, true};
reference = {string, Size - 1, 0};
}
}
StringDataLayout(const StringDataLayout &other) noexcept { *this = other; }
StringDataLayout &operator=(const StringDataLayout &other) noexcept
{
constexpr auto controlBlockSize = sizeof(ControlBlock<MaximumShortStringDataAreaSize>);
auto shortStringLayoutSize = other.control.stringSize() + controlBlockSize;
constexpr auto referenceLayoutSize = sizeof(ReferenceLayout);
std::memcpy(this, &other, std::max(shortStringLayoutSize, referenceLayoutSize));
return *this;
}
constexpr static size_type shortStringCapacity() noexcept
{
return MaximumShortStringDataAreaSize;
}
constexpr void reset() { control = ControlBlock<MaximumShortStringDataAreaSize>(); }
#pragma pack(push)
#pragma pack(1)
ControlBlock<MaximumShortStringDataAreaSize> control;
union {
char shortString[MaximumShortStringDataAreaSize];
struct
{
char dummy[sizeof(void *) - sizeof(ControlBlock<MaximumShortStringDataAreaSize>)];
ReferenceLayout reference;
};
};
#pragma pack(pop)
};
} // namespace Internal
} // namespace Utils
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