eb793d2b82
* Help the compiler optimize unaligned_type. This fixes a regression in 266b0f99 when the type was made constexpr. When switching to a loop to construct the value the compiler was unable to detect what was going on. We now unroll the loop at compile time into what's essentially a hand rolled shift and OR operation which the compiler detects and replaces with a byte swap. Tested on gcc (x86+arm) and clang (x86). Introduce a static value_from which can be used to convert a value from an existing buffer. There were previously three options for this, all bad or awkward in different ways: - val = etl::be_uint32_t(address) Copies to temporary storage. - val = *reinterpret_cast<const etl::be_uint32_t*>(address); Unreadable. - etl::be_uint32_t::copy_store_to_value(address, output); Requires an output parameter. The new addition is: - val = etl::be_uint32_t::value_from(address); Additionally, update the documentation with value_from and the missing, existing constructors. * Please clang-format. --------- Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com>
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{{< callout type="info">}}
Header: unaligned_type.h
From: 20.23.0
{{< /callout >}}
A wrapper for fundamental types around unaligned internal storage.
Allows big and little endian storage.
Marked as packed for MSVC, GCC amd Clang.
template <typename T, int Endian>
class unaligned_type
Where Endian is etl::endian::big or etl::endian::little.
For C++11 or above
template <typename T, int Endian>
using unaligned_type_t = typename etl::unaligned_type<T, Endian>::type;
For C++17 or above
template <typename T, int Endian>
constexpr size_t unaligned_type_v = etl::unaligned_type<T, Endian>::Size;
The following types are predefined.
Host order
Only defined if ETL_ENDIANNESS_IS_CONSTEXPR.
host_char_t
host_schar_t
host_uchar_t
host_short_t
host_ushort_t
host_int_t
host_uint_t
host_long_t
host_ulong_t
host_long_long_t
host_ulong_long_t
host_int8_t ETL_USING_8BIT_TYPES
host_uint8_t ETL_USING_8BIT_TYPES
host_int16_t
host_uint16_t
host_int32_t
host_uint32_t
host_int64_t ETL_USING_64BIT_TYPES
host_uint64_t ETL_USING_64BIT_TYPES
host_float_t
host_double_t
host_long_double_t
Little Endian
le_char_t
le_schar_t
le_uchar_t
le_short_t
le_ushort_t
le_int_t
le_uint_t
le_long_t
le_ulong_t
le_long_long_t
le_ulong_long_t
le_int8_t ETL_USING_8BIT_TYPES
le_uint8_t ETL_USING_8BIT_TYPES
le_int16_t
le_uint16_t
le_int32_t
le_uint32_t
le_int64_t ETL_USING_64BIT_TYPES
le_uint64_t ETL_USING_64BIT_TYPES
le_float_t
le_double_t
le_long_double_t
Big Endian
be_char_t
be_schar_t
be_uchar_t
be_short_t
be_ushort_t
be_int_t
be_uint_t
be_long_t
be_ulong_t
be_long_long_t
be_ulong_long_t
be_int8_t ETL_USING_8BIT_TYPES
be_uint8_t ETL_USING_8BIT_TYPES
be_int16_t
be_uint16_t
be_int32_t
be_uint32_t
be_int64_t ETL_USING_64BIT_TYPES
be_uint64_t ETL_USING_64BIT_TYPES
be_float_t
be_double_t
be_long_double_t
Network Order
Synonym for Big Endian
using net_char_t = be_char_t
using net_schar_t = be_schar_t
using net_uchar_t = be_uchar_t
using net_short_t = be_short_t
using net_ushort_t = be_ushort_t
using net_int_t = be_int_t
using be_uint_t = net_uint_t
using net_long_t = be_long_t
using net_ulong_t = be_ulong_t
using net_long_long_t = be_long_long_t
using net_ulong_long_t = be_ulong_long_t
using net_int8_t = be_int8_t ETL_USING_8BIT_TYPES
using net_uint8_t = be_uint8_t ETL_USING_8BIT_TYPES
using net_int16_t = be_int16_t
using net_uint16_t = be_uint16_t
using net_int32_t = be_int32_t
using net_uint32_t = be_uint32_t
using net_int64_t = be_int64_t ETL_USING_64BIT_TYPES
using net_uint64_t = be_uint64_t ETL_USING_64BIT_TYPES
using net_float_t = be_float_t
using net_double_t = be_double_t
using net_long_double_t = be_long_double_t
Constants
int Endian
The endianness of the type.
size_t Size
The size, in char, of the type.
Constructors
ETL_CONSTEXPR unaligned_type()
Description
Constructs an uninitialised unaligned_type.
unaligned_type(T value)
Description
Constructs with the supplied value.
unaligned_type(const void* address)
Description
Constructs from the Size bytes at the address.
From: 20.39.5
unaligned_type(const void* address, size_t buffer_size)
Description
Constructs from the Size bytes at the address.
buffer_size must be greater than or equal to Size. This is a precondition,
checked by ETL_ASSERT. If checks are disabled then a smaller buffer size
results in a read beyond the end of the buffer.
From: 20.39.5
ETL_CONSTEXPR14 unaligned_type(const unsigned char* address)
Description
Constructs from the Size bytes at the address.
Unlike the const void* overload, this requires no reinterpret_cast and so
may be used in a constexpr context.
From: 20.48.1
ETL_CONSTEXPR14 unaligned_type(const unsigned char* address, size_t buffer_size)
Description
Constructs from the Size bytes at the address.
buffer_size must be greater than or equal to Size. This is a precondition,
checked by ETL_ASSERT. If checks are disabled then a smaller buffer size
results in a read beyond the end of the buffer.
From: 20.48.1
template <int Endian_Other>
unaligned_type(const unaligned_type<T, Endian_Other>& other)
Description
Constructs from another unaligned_type.
The endianness is converted, if necessary.
Member types
using storage_type = unsigned char;
using pointer = unsigned char*;
using const_pointer = const unsigned char*;
using iterator = unsigned char*;
using const_iterator = const unsigned char*;
using reverse_iterator = etl::reverse_iterator<iterator>;
using const_reverse_iterator = etl::reverse_iterator<const_iterator>;
Member functions
pointer data()
Description
Pointer to the beginning of the storage.
ETL_CONSTEXPR14 const_pointer data() const
Description
Const pointer to the beginning of the storage.
ETL_CONSTEXPR14 size_t size() const
Description
Size of the storage.
iterator begin()
Description
Iterator to the beginning of the storage.
ETL_CONSTEXPR14 const_iterator begin() const
Description
Const iterator to the beginning of the storage.
ETL_CONSTEXPR14 const_iterator cbegin() const
Description
Const iterator to the beginning of the storage.
reverse_iterator rbegin()
Description
Reverse iterator to the beginning of the storage.
ETL_CONSTEXPR14 const_reverse_iterator rbegin() const
Description
Const reverse iterator to the beginning of the storage.
ETL_CONSTEXPR14 const_reverse_iterator crbegin() const
Description
Const reverse iterator to the beginning of the storage.
iterator end()
Description
Iterator to the end of the storage.
ETL_CONSTEXPR14 const_iterator end() const
Description
Const iterator to the end of the storage.
ETL_CONSTEXPR14 const_iterator cend() const
Description
Const iterator to the end of the storage.
reverse_iterator rend()
Description
Reverse iterator to the end of the storage.
ETL_CONSTEXPR14 const_reverse_iterator rend() const
Description
Const reverse iterator to the end of the storage.
ETL_CONSTEXPR14 const_reverse_iterator crend() const
Description
Const reverse iterator to the end of the storage.
storage_type& operator[](int i)
Description
Index operator.
ETL_CONSTEXPR14 const storage_type& operator[](int i) const
Description
Const index operator.
ETL_CONSTEXPR14 unaligned_type& operator =(T value)
Description
Assignment operator.
ETL_CONSTEXPR14 operator T() const
Description
Conversion operator.
ETL_CONSTEXPR14 T value() const
Description
Gets the value.
static ETL_CONSTEXPR14 T value_from(const_pointer address)
Description
Gets the value of the Size bytes at the address.
Unlike construction from an address, the bytes are not copied to storage first.
template <int Endian_Other>
ETL_CONSTEXPR14 unaligned_type& operator =(const unaligned_type<T, Endian_Other>& other)
Description
Assignment operator from other endianness.
ETL_CONSTEXPR14 bool operator ==(const unaligned_type& lhs, const unaligned_type& rhs)
Description
Equality operator.
Removed: 20.39.3
ETL_CONSTEXPR14 bool operator ==(const unaligned_type& lhs, T rhs)
Description
Equality operator.
Removed: 20.39.3
ETL_CONSTEXPR14 bool operator ==(T lhs, const unaligned_type& rhs)
Description
Equality operator.
Removed: 20.39.3
ETL_CONSTEXPR14 bool operator !=(const unaligned_type& lhs, T rhs)
Description
Inequality operator.
Removed: 20.39.3
ETL_CONSTEXPR14 bool operator !=(const unaligned_type& lhs, const unaligned_type& rhs)
Description
Inequality operator.
Removed: 20.39.3
ETL_CONSTEXPR14 bool operator !=(T lhs, const unaligned_type& rhs)
Description
Inequality operator.
Removed: 20.39.3