Encoding Scheme

The encoding_scheme template turns any encoding into a byte-based encoding capable of reading and writing those bytes into and out of byte-value_type ranges. It prevents duplicating effort to read encodings as little endian or big endian, allowing composition for any desired encoding to interface with e.g. a UTF-16 Big Endian blob of data coming over a network or shared pipe.

Aliases

using ztd::text::basic_utf16_le = encoding_scheme<utf16_t, endian::little, _Byte>

A UTF-16 encoding, in Little Endian format, with inputs as a sequence of bytes.

Template Parameters: _Byte – The byte type to use. Typically, this is std::byte or uchar.

using ztd::text::utf16_le_t = basic_utf16_le<::std::byte>: A UTF-16 encoding, in Little Endian format, with inputs as a sequence of bytes.

using ztd::text::basic_utf16_be = encoding_scheme<utf16_t, endian::big, _Byte>

A UTF-16 encoding, in Big Endian format, with inputs as a sequence of bytes.

Template Parameters: _Byte – The byte type to use. Typically, this is std::byte or unsigned char.

using ztd::text::utf16_be_t = basic_utf16_be<::std::byte>: A UTF-16 encoding, in Big Endian format, with inputs as a sequence of bytes.

using ztd::text::basic_utf16_ne = encoding_scheme<utf16_t, endian::native, _Byte>

A UTF-16 encoding, in Native Endian format, with inputs as a sequence of bytes.

Template Parameters: _Byte – The byte type to use. Typically, this is std::byte or unsigned char.

using ztd::text::utf16_ne_t = basic_utf16_ne<::std::byte>: A UTF-16 encoding, in Native Endian format, with inputs as a sequence of bytes.

using ztd::text::basic_utf32_le = encoding_scheme<utf32_t, endian::little, _Byte>

A UTF-32 encoding, in Little Endian format, with inputs as a sequence of bytes.

Template Parameters: _Byte – The byte type to use. Typically, this is std::byte or unsigned char .

using ztd::text::utf32_le_t = basic_utf32_le<::std::byte>: A UTF-32 encoding, in Little Endian format, with inputs as a sequence of bytes.

using ztd::text::basic_utf32_be = encoding_scheme<utf32_t, endian::big, _Byte>

A UTF-32 encoding, in Big Endian format, with inputs as a sequence of bytes.

Template Parameters: _Byte – The byte type to use. Typically, this is std::byte or unsigned char .

using ztd::text::utf32_be_t = basic_utf32_be<::std::byte>: A UTF-32 encoding, in Big Endian format, with inputs as a sequence of bytes.

using ztd::text::basic_utf32_ne = encoding_scheme<utf32_t, endian::native, _Byte>

A UTF-32 encoding, in Native Endian format, with inputs as a sequence of bytes.

Template Parameters: _Byte – The byte type to use. Typically, this is std::byte or unsigned char .

using ztd::text::utf32_ne_t = basic_utf32_ne<::std::byte>: A UTF-32 encoding, in Big Endian format, with inputs as a sequence of bytes.

Base Template

template<typename _Encoding, endian _Endian = endian::native, typename _Byte = ::std::byte> class encoding_scheme : public __txt_detail::__is_unicode_encoding_es<encoding_scheme<_Encoding, _Endian, _Byte>, unwrap_remove_cvref_t<_Encoding>>, private ebco<_Encoding>

Decomposes the provided Encoding type into a specific endianness (big, little, or native) to allow for a single encoding type to be viewed in different ways.

Remark

For example, this can be used to construct a Big Endian UTF-16 by using encoding_scheme<ztd::text::utf16_t, ztd::endian::big>. It can be made interopable with unsigned char buffers rather than std::byte buffers by doing: ztd::text::encoding_scheme<ztd::text::utf32_t, ztd::endian::native, unsigned char>.

Template Parameters

_Encoding – The encoding type.
_Endian – The endianess to use. Defaults to ztd::endian::native.
_Byte – The byte type to use. Defaults to std::byte.

Public Types

using encoding_type = _Encoding 

The encoding type. ///.

The encoding type that this scheme wraps.

using code_point = code_point_t<_UBaseEncoding>: The individual units that result from a decode operation or as used as input to an encode operation. For most encodings, this is going to be a Unicode Code Point or a Unicode Scalar Value.

using code_unit = _Byte 

The individual units that result from an encode operation or are used as input to a decode operation.

Remark

Typically, this type is usually always some kind of byte type (unsigned char or std::byte or other sizeof(obj) == 1 type)./

using decode_state = decode_state_t<_UBaseEncoding>

The state that can be used between calls to the decode function.

Remark

Even if the underlying encoding only has a single state type, we need to separate the two out in order to generically handle all encodings. Therefore, the encoding_scheme will always have both encode_state and decode_state.

using encode_state = encode_state_t<_UBaseEncoding>

The state that can be used between calls to the encode function.

Remark

Even if the underlying encoding only has a single state type, we need to separate the two out in order to generically handle all encodings. Therefore, the encoding_scheme will always have both encode_state and decode_state.

using is_encode_injective = ::std::integral_constant<bool, is_encode_injective_v<_UBaseEncoding>>

Whether or not the encode operation can process all forms of input into code point values.

Remark

Defers to what the underlying encoding_type does.

using is_decode_injective = ::std::integral_constant<bool, is_decode_injective_v<_UBaseEncoding>>

Whether or not the decode operation can process all forms of input into code point values.

Remark

Defers to what the underlying encoding_type does.

Public Functions

encoding_scheme() = default: Default constructs a ztd::text::encoding_scheme.

template<typename _Arg0, typename ..._Args, ::std::enable_if_t<!::std::is_same_v<remove_cvref_t<_Arg0>, encoding_scheme> && !::std::is_same_v<remove_cvref_t<_Arg0>, ::std::in_place_t>>* = nullptr> inline constexpr encoding_scheme(_Arg0 &&__arg0, _Args&&... __args) noexcept(::std::is_nothrow_constructible_v<_UBaseEncoding, _Arg0, _Args...>)

Constructs a ztd::text::encoding_scheme with the encoding object and any additional arguments.

Parameters

__arg0 – [in] The first argument used to construct the stored encoding.
__args – [in] Any additional arguments used to construct the stored encoding.

template<typename ..._Args> inline constexpr encoding_scheme(::std::in_place_t, _Args&&... __args) noexcept(::std::is_nothrow_constructible_v<_UBaseEncoding, _Args...>)

Constructs a ztd::text::encoding_scheme with the encoding object and any additional arguments.

Remark

If the provided encoding does not have a byte code_unit type, it is wrapped in an ztd::text::encoding_scheme first.

Parameters: __args – [in] Any additional arguments used to construct the encoding in the erased storage.

encoding_scheme(const encoding_scheme&) = default: Cannot copy-construct a ztd::text::encoding_scheme object.

encoding_scheme &operator=(const encoding_scheme&) = default: Cannot copy-assign a ztd::text::encoding_scheme object.

encoding_scheme(encoding_scheme&&) = default

Move-constructs a ztd::text::encoding_scheme from the provided r-value reference.

Remark

This leaves the passed-in r-value reference without an encoding object. Calling any function on a moved-fron ztd::text::encoding_scheme, except for destruction, is a violation and invokes Undefined Behavior (generally, a crash).

encoding_scheme &operator=(encoding_scheme&&) = default

Move-assigns a ztd::text::encoding_scheme from the provided r-value reference.

Remark

This leaves the passed-in r-value reference without an encoding object. Calling any function on a moved-fron ztd::text::encoding_scheme, except for destruction, is a violation and may invoke Undefined Behavior (generally, a crash).

inline constexpr encoding_type &base() & noexcept

Retrives the underlying encoding object.

Returns: An l-value reference to the encoding object.

inline constexpr const encoding_type &base() const & noexcept

Retrives the underlying encoding object.

Returns: An l-value reference to the encoding object.

inline constexpr encoding_type &&base() && noexcept

Retrives the underlying encoding object.

Returns: An l-value reference to the encoding object.

template<typename _Unused = encoding_type, ::std::enable_if_t<is_code_units_replaceable_v<_Unused>>* = nullptr> inline decltype(auto) constexpr replacement_code_units() const noexcept

Returns, the desired replacement code units to use.

Remark

This is only callable if the function call exists on the wrapped encoding. It is broken down into a contiguous view type formulated from bytes if the wrapped code unit types do not match.

template<typename _Unused = encoding_type, ::std::enable_if_t<is_code_points_replaceable_v<_Unused>>* = nullptr> inline decltype(auto) constexpr replacement_code_points() const noexcept

Returns the desired replacement code points to use.

Remark

Is only callable if the function call exists on the wrapped encoding.

template<typename _Unused = encoding_type, ::std::enable_if_t<is_code_units_maybe_replaceable_v<_Unused>>* = nullptr> inline decltype(auto) constexpr maybe_replacement_code_units() const noexcept

Returns the desired replacement code units to use, or an empty optional-like type if there is nothing present.

Remark

This is only callable if the function call exists on the wrapped encoding. It is broken down into a contiguous view type formulated from bytes if the wrapped code unit types do not match.

template<typename _Unused = encoding_type, ::std::enable_if_t<is_code_points_maybe_replaceable_v<_Unused>>* = nullptr> inline decltype(auto) constexpr maybe_replacement_code_points() const noexcept

Returns the desired replacement code units to use.

Remark

This Is only callable if the function call exists on the wrapped encoding.

inline constexpr bool contains_unicode_encoding() const noexcept: Whether or not this encoding is some form of Unicode encoding.

template<typename _Result, typename _InputProgress, typename _OutputProgress, ::std::enable_if_t<is_input_error_skippable_v<const encoding_type&, _Result, const _InputProgress&, const _OutputProgress&>>* = nullptr> inline decltype(auto) constexpr skip_input_error(_Result &&__result) const noexcept(::ztd::text::is_nothrow_skip_input_error_v<const encoding_type&, _Result, const _InputProgress&, const _OutputProgress&>)

Skips any consecutive input errors in the encoded input, where possible.

Remark

This Is only callable if the function call exists on the wrapped encoding.

template<typename _Input, typename _Output, typename _ErrorHandler> inline constexpr auto decode_one(_Input &&__input, _Output &&__output, _ErrorHandler &&__error_handler, decode_state &__s) const

Decodes a single complete unit of information as code points and produces a result with the input and output ranges moved past what was successfully read and written; or, produces an error and returns the input and output ranges untouched.

Remark

To the best ability of the implementation, the iterators will be returned untouched (e.g., the input models at least a view and a forward_range). If it is not possible, returned ranges may be incremented even if an error occurs due to the semantics of any view that models an input_range.

Parameters

__input – [in] The input view to read code uunits from.
__output – [in] The output view to write code points into.
__error_handler – [in] The error handler to invoke if encoding fails.
__s – [inout] The necessary state information. For this encoding, the state is empty and means very little.

Returns

A ztd::text::decode_result object that contains the input range, output range, error handler, and a reference to the passed-in state.

template<typename _Input, typename _Output, typename _ErrorHandler> inline constexpr auto encode_one(_Input &&__input, _Output &&__output, _ErrorHandler &&__error_handler, encode_state &__s) const

Encodes a single complete unit of information as code units and produces a result with the input and output ranges moved past what was successfully read and written; or, produces an error and returns the input and output ranges untouched.

Remark

To the best ability of the implementation, the iterators will be returned untouched (e.g., the input models at least a view and a forward_range). If it is not possible, returned ranges may be incremented even if an error occurs due to the semantics of any view that models an input_range.

Parameters

__input – [in] The input view to read code points from.
__output – [in] The output view to write code units into.
__error_handler – [in] The error handler to invoke if encoding fails.
__s – [inout] The necessary state information. For this encoding, the state is empty and means very little.

Returns

A ztd::text::encode_result object that contains the input range, output range, error handler, and a reference to the passed-in state.

Public Static Attributes

static constexprconst::std::size_t max_code_points = max_code_points_v<_UBaseEncoding>: The maximum number of code points a single complete operation of decoding can produce. This is 1 for all Unicode Transformation Format (UTF) encodings.

static constexprconst::std::size_t max_code_units = (max_code_units_v<_UBaseEncoding> * sizeof(_BaseCodeUnit)) / (sizeof(_Byte)): The maximum code units a single complete operation of encoding can produce.

static constexprconst::ztd::text_encoding_id decoded_id = decoded_id_v<_UBaseEncoding>: The id representing the decoded text.

static constexprconst::ztd::text_encoding_id encoded_id = ::ztd::to_byte_text_encoding_id(encoded_id_v<_UBaseEncoding>, _Endian, sizeof(code_unit_t<_UBaseEncoding>)): The id representing the encoded text.