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Endian: constexpr constructors and conversion operators

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Problem:
- Constructors and conversion operators are not `constexpr`,
  but they can be.
- `constexpr` is needed here so that other classes can add `constexpr`
  evaluation.

Solution:
- Add the `constexpr` keyword to the constructors and
  conversion operators.
- Add `static_assert` tests which ensure the capability works.
This commit is contained in:
Lenny Maiorani 2020-10-08 09:38:31 -04:00 committed by Andreas Kling
parent e8da5f99b1
commit 151b8b5984
2 changed files with 47 additions and 8 deletions
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16
AK/Endian.h
View file

@ -32,7 +32,7 @@
namespace AK {
template<typename T>
ALWAYS_INLINE T convert_between_host_and_little_endian(T value)
ALWAYS_INLINE constexpr T convert_between_host_and_little_endian(T value)
{
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
return value;
@ -49,7 +49,7 @@ ALWAYS_INLINE T convert_between_host_and_little_endian(T value)
}
template<typename T>
ALWAYS_INLINE T convert_between_host_and_big_endian(T value)
ALWAYS_INLINE constexpr T convert_between_host_and_big_endian(T value)
{
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
if constexpr (sizeof(T) == 8)
@ -87,14 +87,14 @@ public:
friend InputStream& operator>><T>(InputStream&, LittleEndian<T>&);
friend OutputStream& operator<<<T>(OutputStream&, LittleEndian<T>);
LittleEndian() { }
constexpr LittleEndian() { }
LittleEndian(T value)
constexpr LittleEndian(T value)
: m_value(convert_between_host_and_little_endian(value))
{
}
operator T() const { return convert_between_host_and_little_endian(m_value); }
constexpr operator T() const { return convert_between_host_and_little_endian(m_value); }
private:
T m_value { 0 };
@ -116,14 +116,14 @@ public:
friend InputStream& operator>><T>(InputStream&, BigEndian<T>&);
friend OutputStream& operator<<<T>(OutputStream&, BigEndian<T>);
BigEndian() { }
constexpr BigEndian() = default;
BigEndian(T value)
constexpr BigEndian(T value)
: m_value(convert_between_host_and_big_endian(value))
{
}
operator T() const { return convert_between_host_and_big_endian(m_value); }
constexpr operator T() const { return convert_between_host_and_big_endian(m_value); }
private:
T m_value { 0 };

39
AK/Tests/TestEndian.cpp Normal file
View file

@ -0,0 +1,39 @@
/*
* Copyright (c) 2020, the SerenityOS developers.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/TestSuite.h>
#include <AK/Endian.h>
static_assert(BigEndian<u32> {} == 0, "Big endian values should be default constructed in a constexpr context.");
static_assert(BigEndian<u32> { 42 } == 42, "Big endian values should be value constructed in a constexpr context.");
static_assert(LittleEndian<u32> {} == 0, "Little endian values should be default constructed in a constexpr context.");
static_assert(LittleEndian<u32> { 42 } == 42, "Little endian values should be value constructed in a constexpr context.");
TEST_MAIN(Endian);