mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-04 21:42:39 +00:00
227 lines
5.9 KiB
C++
227 lines
5.9 KiB
C++
//
|
|
// Alignment.h
|
|
//
|
|
// Library: Foundation
|
|
// Package: Dynamic
|
|
// Module: Alignment
|
|
//
|
|
// Definition of the Alignment class.
|
|
//
|
|
// Copyright (c) 2007, Applied Informatics Software Engineering GmbH.
|
|
// and Contributors.
|
|
//
|
|
// SPDX-License-Identifier: BSL-1.0
|
|
//
|
|
|
|
|
|
// Adapted for POCO from LLVM Compiler Infrastructure code:
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source License
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file defines the AlignOf function that computes alignments for
|
|
// arbitrary types.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
|
|
#ifndef Foundation_AlignOf_INCLUDED
|
|
#define Foundation_AlignOf_INCLUDED
|
|
|
|
|
|
#include <cstddef>
|
|
|
|
|
|
#ifdef POCO_ENABLE_CPP11
|
|
|
|
|
|
# include <type_traits>
|
|
# define POCO_HAVE_ALIGNMENT
|
|
|
|
|
|
#else
|
|
|
|
|
|
namespace Poco
|
|
{
|
|
|
|
|
|
template <typename T>
|
|
struct AlignmentCalcImpl
|
|
{
|
|
char x;
|
|
T t;
|
|
|
|
private:
|
|
AlignmentCalcImpl() { } // Never instantiate.
|
|
};
|
|
|
|
|
|
template <typename T>
|
|
struct AlignOf
|
|
/// A templated class that contains an enum value representing
|
|
/// the alignment of the template argument. For example,
|
|
/// AlignOf<int>::Alignment represents the alignment of type "int". The
|
|
/// alignment calculated is the minimum alignment, and not necessarily
|
|
/// the "desired" alignment returned by GCC's __alignof__ (for example). Note
|
|
/// that because the alignment is an enum value, it can be used as a
|
|
/// compile-time constant (e.g., for template instantiation).
|
|
{
|
|
enum
|
|
{
|
|
Alignment = static_cast<unsigned int>(sizeof(AlignmentCalcImpl<T>) - sizeof(T))
|
|
};
|
|
|
|
enum
|
|
{
|
|
Alignment_GreaterEqual_2Bytes = Alignment >= 2 ? 1 : 0
|
|
};
|
|
enum
|
|
{
|
|
Alignment_GreaterEqual_4Bytes = Alignment >= 4 ? 1 : 0
|
|
};
|
|
enum
|
|
{
|
|
Alignment_GreaterEqual_8Bytes = Alignment >= 8 ? 1 : 0
|
|
};
|
|
enum
|
|
{
|
|
Alignment_GreaterEqual_16Bytes = Alignment >= 16 ? 1 : 0
|
|
};
|
|
|
|
enum
|
|
{
|
|
Alignment_LessEqual_2Bytes = Alignment <= 2 ? 1 : 0
|
|
};
|
|
enum
|
|
{
|
|
Alignment_LessEqual_4Bytes = Alignment <= 4 ? 1 : 0
|
|
};
|
|
enum
|
|
{
|
|
Alignment_LessEqual_8Bytes = Alignment <= 8 ? 1 : 0
|
|
};
|
|
enum
|
|
{
|
|
Alignment_LessEqual_16Bytes = Alignment <= 16 ? 1 : 0
|
|
};
|
|
};
|
|
|
|
|
|
template <typename T>
|
|
inline unsigned alignOf()
|
|
/// A templated function that returns the minimum alignment of
|
|
/// of a type. This provides no extra functionality beyond the AlignOf
|
|
/// class besides some cosmetic cleanliness. Example usage:
|
|
/// alignOf<int>() returns the alignment of an int.
|
|
{
|
|
return AlignOf<T>::Alignment;
|
|
}
|
|
|
|
|
|
template <std::size_t Alignment>
|
|
struct AlignedCharArrayImpl;
|
|
/// Helper for building an aligned character array type.
|
|
///
|
|
/// This template is used to explicitly build up a collection of aligned
|
|
/// character types. We have to build these up using a macro and explicit
|
|
/// specialization to cope with old versions of MSVC and GCC where only an
|
|
/// integer literal can be used to specify an alignment constraint. Once built
|
|
/// up here, we can then begin to indirect between these using normal C++
|
|
/// template parameters.
|
|
|
|
|
|
// MSVC requires special handling here.
|
|
|
|
|
|
# if __has_feature(cxx_alignas)
|
|
# define POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
|
|
template <> \
|
|
struct AlignedCharArrayImpl<x> \
|
|
{ \
|
|
char aligned alignas(x); \
|
|
}
|
|
# define POCO_HAVE_ALIGNMENT
|
|
# endif
|
|
|
|
|
|
# ifdef POCO_HAVE_ALIGNMENT
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(1);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(2);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(4);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(8);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(16);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(32);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(64);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(512);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(1024);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(2048);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(4096);
|
|
POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(8192);
|
|
|
|
# undef POCO_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
|
|
# endif // POCO_HAVE_ALIGNMENT
|
|
|
|
|
|
// POCO_HAVE_ALIGNMENT will be defined on the pre-C++11 platforms/compilers where
|
|
// it can be reliably determined and used. Uncomment the line below to explicitly
|
|
// disable use of alignment even for those platforms.
|
|
// #undef POCO_HAVE_ALIGNMENT
|
|
|
|
|
|
# ifdef POCO_HAVE_ALIGNMENT
|
|
|
|
template <typename T1, typename T2 = char, typename T3 = char, typename T4 = char>
|
|
union AlignedCharArrayUnion
|
|
/// This union template exposes a suitably aligned and sized character
|
|
/// array member which can hold elements of any of up to four types.
|
|
///
|
|
/// These types may be arrays, structs, or any other types. The goal is to
|
|
/// produce a union type containing a character array which, when used, forms
|
|
/// storage suitable to placement new any of these types over. Support for more
|
|
/// than four types can be added at the cost of more boiler plate.
|
|
{
|
|
private:
|
|
class AlignerImpl
|
|
{
|
|
T1 t1;
|
|
T2 t2;
|
|
T3 t3;
|
|
T4 t4;
|
|
|
|
AlignerImpl(); // Never defined or instantiated.
|
|
};
|
|
|
|
union SizerImpl
|
|
{
|
|
char arr1[sizeof(T1)];
|
|
char arr2[sizeof(T2)];
|
|
char arr3[sizeof(T3)];
|
|
char arr4[sizeof(T4)];
|
|
};
|
|
|
|
public:
|
|
char buffer[sizeof(SizerImpl)];
|
|
/// The character array buffer for use by clients.
|
|
///
|
|
/// No other member of this union should be referenced. They exist purely to
|
|
/// constrain the layout of this character array.
|
|
|
|
private:
|
|
Poco::AlignedCharArrayImpl<AlignOf<AlignerImpl>::Alignment> _nonceMember;
|
|
};
|
|
|
|
# endif // POCO_HAVE_ALIGNMENT
|
|
|
|
} // namespace Poco
|
|
|
|
|
|
#endif // POCO_ENABLE_CPP11
|
|
|
|
|
|
#endif // Foundation_AlignOf_INCLUDED
|