//
// Copyright (c) 2015 Artyom Beilis (Tonkikh)
// Copyright (c) 2021-2023 Alexander Grund
//
// Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt
#ifndef BOOST_LOCALE_GENERIC_CODECVT_HPP
#define BOOST_LOCALE_GENERIC_CODECVT_HPP
#include <boost/locale/utf.hpp>
#include <cstdint>
#include <locale>
namespace boost { namespace locale {
static_assert(sizeof(std::mbstate_t) >= 2, "std::mbstate_t is to small to store an UTF-16 codepoint");
namespace detail {
// Avoid including cstring for std::memcpy
inline void copy_uint16_t(void* dst, const void* src)
{
unsigned char* cdst = static_cast<unsigned char*>(dst);
const unsigned char* csrc = static_cast<const unsigned char*>(src);
cdst[0] = csrc[0];
cdst[1] = csrc[1];
}
inline uint16_t read_state(const std::mbstate_t& src)
{
uint16_t dst;
copy_uint16_t(&dst, &src);
return dst;
}
inline void write_state(std::mbstate_t& dst, const uint16_t src)
{
copy_uint16_t(&dst, &src);
}
} // namespace detail
/// \brief A base class that used to define constants for generic_codecvt
class generic_codecvt_base {
public:
/// Initial state for converting to or from Unicode code points, used by initial_state in derived classes
enum initial_convertion_state {
to_unicode_state, ///< The state would be used by to_unicode functions
from_unicode_state ///< The state would be used by from_unicode functions
};
};
/// \brief Generic codecvt facet for various stateless encodings to UTF-16 and UTF-32 using wchar_t, char32_t
/// and char16_t
///
/// Implementations should derive from this class defining itself as CodecvtImpl and provide following members
///
/// - `state_type` - a type of special object that allows to store intermediate cached data, for example `iconv_t`
/// descriptor
/// - `state_type initial_state(generic_codecvt_base::initial_convertion_state direction) const` - member function
/// that creates initial state
/// - `int max_encoding_length() const` - a maximal length that one Unicode code point is represented, for UTF-8 for
/// example it is 4 from ISO-8859-1 it is 1
/// - `utf::code_point to_unicode(state_type& state, const char*& begin, const char* end)` - extract first code
/// point from the text in range [begin,end), in case of success begin would point to the next character sequence to
/// be encoded to next code point, in case of incomplete sequence - utf::incomplete shell be returned, and in case
/// of invalid input sequence utf::illegal shell be returned and begin would remain unmodified
/// - `utf::len_or_error from_unicode(state_type &state, utf::code_point u, char* begin, const char* end)` - convert
/// a Unicode code point `u` into a character sequence at [begin,end). Return the length of the sequence in case of
/// success, utf::incomplete in case of not enough room to encode the code point, or utf::illegal in case conversion
/// can not be performed
///
///
/// For example implementation of codecvt for latin1/ISO-8859-1 character set
///
/// \code
///
/// template<typename CharType>
/// class latin1_codecvt: boost::locale::generic_codecvt<CharType,latin1_codecvt<CharType> >
/// {
/// public:
///
/// /* Standard codecvt constructor */
/// latin1_codecvt(size_t refs = 0): boost::locale::generic_codecvt<CharType,latin1_codecvt<CharType> >(refs)
/// {
/// }
///
/// /* State is unused but required by generic_codecvt */
/// struct state_type {};
///
/// state_type initial_state(generic_codecvt_base::initial_convertion_state /*unused*/) const
/// {
/// return state_type();
/// }
///
/// int max_encoding_length() const
/// {
/// return 1;
/// }
///
/// boost::locale::utf::code_point to_unicode(state_type&, const char*& begin, const char* end) const
/// {
/// if(begin == end)
/// return boost::locale::utf::incomplete;
/// return *begin++;
/// }
///
/// boost::locale::utf::len_or_error from_unicode(state_type&, boost::locale::utf::code_point u,
/// char* begin, const char* end) const
/// {
/// if(u >= 256)
/// return boost::locale::utf::illegal;
/// if(begin == end)
/// return boost::locale::utf::incomplete;
/// *begin = u;
/// return 1;
/// }
/// };
///
/// \endcode
///
/// When external tools used for encoding conversion, the `state_type` is useful to save objects used for
/// conversions. For example, icu::UConverter can be saved in such a state for an efficient use:
///
/// \code
/// template<typename CharType>
/// class icu_codecvt: boost::locale::generic_codecvt<CharType,icu_codecvt<CharType>>
/// {
/// public:
///
/// /* Standard codecvt constructor */
/// icu_codecvt(std::string const &name,refs = 0):
/// boost::locale::generic_codecvt<CharType,icu_codecvt<CharType>>(refs)
/// { ... }
///
/// using state_type = std::unique_ptr<UConverter,void (*)(UConverter*)>;
///
/// state_type initial_state(generic_codecvt_base::initial_convertion_state /*unused*/) const
/// {
/// UErrorCode err = U_ZERO_ERROR;
/// return state_type(ucnv_safeClone(converter_,0,0,&err),ucnv_close);
/// }
///
/// boost::locale::utf::code_point to_unicode(state_type &ptr,char const *&begin,char const *end) const
/// {
/// UErrorCode err = U_ZERO_ERROR;
/// boost::locale::utf::code_point cp = ucnv_getNextUChar(ptr.get(),&begin,end,&err);
/// ...
/// }
/// ...
/// };
/// \endcode
///
template<typename CharType, typename CodecvtImpl, int CharSize = sizeof(CharType)>
class generic_codecvt;
/// \brief UTF-16 to/from narrow char codecvt facet to use with char16_t or wchar_t on Windows
///
/// Note in order to fit the requirements of usability by std::wfstream it uses mbstate_t
/// to handle intermediate states in handling of variable length UTF-16 sequences
///
/// Its member functions implement standard virtual functions of basic codecvt
template<typename CharType, typename CodecvtImpl>
class generic_codecvt<CharType, CodecvtImpl, 2> : public std::codecvt<CharType, char, std::mbstate_t>,
public generic_codecvt_base {
public:
typedef CharType uchar;
generic_codecvt(size_t refs = 0) : std::codecvt<CharType, char, std::mbstate_t>(refs) {}
const CodecvtImpl& implementation() const { return *static_cast<const CodecvtImpl*>(this); }
protected:
std::codecvt_base::result do_unshift(std::mbstate_t& s, char* from, char* /*to*/, char*& next) const override
{
if(*reinterpret_cast<char*>(&s) != 0)
return std::codecvt_base::error;
next = from;
return std::codecvt_base::ok;
}
int do_encoding() const noexcept override { return 0; }
int do_max_length() const noexcept override { return implementation().max_encoding_length(); }
bool do_always_noconv() const noexcept override { return false; }
int do_length(std::mbstate_t& std_state, const char* from, const char* from_end, size_t max) const override
{
bool state = *reinterpret_cast<char*>(&std_state) != 0;
const char* save_from = from;
auto cvt_state = implementation().initial_state(to_unicode_state);
while(max > 0 && from < from_end) {
const char* prev_from = from;
const utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
if(ch == boost::locale::utf::incomplete || ch == boost::locale::utf::illegal) {
from = prev_from;
break;
}
max--;
if(ch > 0xFFFF) {
if(!state)
from = prev_from;
state = !state;
}
}
*reinterpret_cast<char*>(&std_state) = state;
return static_cast<int>(from - save_from);
}
std::codecvt_base::result do_in(std::mbstate_t& std_state,
const char* from,
const char* from_end,
const char*& from_next,
uchar* to,
uchar* to_end,
uchar*& to_next) const override
{
std::codecvt_base::result r = std::codecvt_base::ok;
// mbstate_t is POD type and should be initialized to 0 (i.a. state = stateT())
// according to standard. We use it to keep a flag 0/1 for surrogate pair writing
//
// if 0/false no codepoint above >0xFFFF observed, else a codepoint above 0xFFFF was observed
// and first pair is written, but no input consumed
bool state = *reinterpret_cast<char*>(&std_state) != 0;
auto cvt_state = implementation().initial_state(to_unicode_state);
while(to < to_end && from < from_end) {
const char* from_saved = from;
utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
if(ch == boost::locale::utf::illegal) {
from = from_saved;
r = std::codecvt_base::error;
break;
}
if(ch == boost::locale::utf::incomplete) {
from = from_saved;
r = std::codecvt_base::partial;
break;
}
// Normal codepoints go directly to stream
if(ch <= 0xFFFF)
*to++ = static_cast<uchar>(ch);
else {
// For other codepoints we do the following
//
// 1. We can't consume our input as we may find ourselves
// in state where all input consumed but not all output written,i.e. only
// 1st pair is written
// 2. We only write first pair and mark this in the state, we also revert back
// the from pointer in order to make sure this codepoint would be read
// once again and then we would consume our input together with writing
// second surrogate pair
ch -= 0x10000;
std::uint16_t w1 = static_cast<std::uint16_t>(0xD800 | (ch >> 10));
std::uint16_t w2 = static_cast<std::uint16_t>(0xDC00 | (ch & 0x3FF));
if(!state) {
from = from_saved;
*to++ = w1;
} else
*to++ = w2;
state = !state;
}
}
from_next = from;
to_next = to;
if(r == std::codecvt_base::ok && (from != from_end || state))
r = std::codecvt_base::partial;
*reinterpret_cast<char*>(&std_state) = state;
return r;
}
std::codecvt_base::result do_out(std::mbstate_t& std_state,
const uchar* from,
const uchar* from_end,
const uchar*& from_next,
char* to,
char* to_end,
char*& to_next) const override
{
std::codecvt_base::result r = std::codecvt_base::ok;
// mbstate_t is POD type and should be initialized to 0 (i.a. state = stateT())
// according to standard. We assume that sizeof(mbstate_t) >=2 in order
// to be able to store first observed surrogate pair
//
// State: state!=0 - a first surrogate pair was observed (state = first pair),
// we expect the second one to come and then zero the state
std::uint16_t state = detail::read_state(std_state);
auto cvt_state = implementation().initial_state(from_unicode_state);
while(to < to_end && from < from_end) {
utf::code_point ch = 0;
if(state != 0) {
// if the state indicates that 1st surrogate pair was written
// we should make sure that the second one that comes is actually
// second surrogate
std::uint16_t w1 = state;
std::uint16_t w2 = *from;
// we don't forward from as writing may fail to incomplete or
// partial conversion
if(0xDC00 <= w2 && w2 <= 0xDFFF) {
std::uint16_t vh = w1 - 0xD800;
std::uint16_t vl = w2 - 0xDC00;
ch = ((uint32_t(vh) << 10) | vl) + 0x10000;
} else {
// Invalid surrogate
r = std::codecvt_base::error;
break;
}
} else {
ch = *from;
if(0xD800 <= ch && ch <= 0xDBFF) {
// if this is a first surrogate pair we put
// it into the state and consume it, note we don't
// go forward as it should be illegal so we increase
// the from pointer manually
state = static_cast<uint16_t>(ch);
from++;
continue;
} else if(0xDC00 <= ch && ch <= 0xDFFF) {
// if we observe second surrogate pair and
// first only may be expected we should break from the loop with error
// as it is illegal input
r = std::codecvt_base::error;
break;
}
}
if(!boost::locale::utf::is_valid_codepoint(ch)) {
r = std::codecvt_base::error;
break;
}
const utf::code_point len = implementation().from_unicode(cvt_state, ch, to, to_end);
if(len == boost::locale::utf::incomplete) {
r = std::codecvt_base::partial;
break;
} else if(len == boost::locale::utf::illegal) {
r = std::codecvt_base::error;
break;
} else
to += len;
state = 0;
from++;
}
from_next = from;
to_next = to;
if(r == std::codecvt_base::ok && (from != from_end || state != 0))
r = std::codecvt_base::partial;
detail::write_state(std_state, state);
return r;
}
};
/// \brief UTF-32 to/from narrow char codecvt facet to use with char32_t or wchar_t on POSIX platforms
///
/// Its member functions implement standard virtual functions of basic codecvt.
/// mbstate_t is not used for UTF-32 handling due to fixed length encoding
template<typename CharType, typename CodecvtImpl>
class generic_codecvt<CharType, CodecvtImpl, 4> : public std::codecvt<CharType, char, std::mbstate_t>,
public generic_codecvt_base {
public:
typedef CharType uchar;
generic_codecvt(size_t refs = 0) : std::codecvt<CharType, char, std::mbstate_t>(refs) {}
const CodecvtImpl& implementation() const { return *static_cast<const CodecvtImpl*>(this); }
protected:
std::codecvt_base::result
do_unshift(std::mbstate_t& /*s*/, char* from, char* /*to*/, char*& next) const override
{
next = from;
return std::codecvt_base::ok;
}
int do_encoding() const noexcept override { return 0; }
int do_max_length() const noexcept override { return implementation().max_encoding_length(); }
bool do_always_noconv() const noexcept override { return false; }
int do_length(std::mbstate_t& /*state*/, const char* from, const char* from_end, size_t max) const override
{
const char* start_from = from;
auto cvt_state = implementation().initial_state(to_unicode_state);
while(max > 0 && from < from_end) {
const char* save_from = from;
const utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
if(ch == boost::locale::utf::incomplete || ch == boost::locale::utf::illegal) {
from = save_from;
break;
}
max--;
}
return static_cast<int>(from - start_from);
}
std::codecvt_base::result do_in(std::mbstate_t& /*state*/,
const char* from,
const char* from_end,
const char*& from_next,
uchar* to,
uchar* to_end,
uchar*& to_next) const override
{
std::codecvt_base::result r = std::codecvt_base::ok;
auto cvt_state = implementation().initial_state(to_unicode_state);
while(to < to_end && from < from_end) {
const char* from_saved = from;
const utf::code_point ch = implementation().to_unicode(cvt_state, from, from_end);
if(ch == boost::locale::utf::illegal) {
r = std::codecvt_base::error;
from = from_saved;
break;
}
if(ch == boost::locale::utf::incomplete) {
r = std::codecvt_base::partial;
from = from_saved;
break;
}
*to++ = ch;
}
from_next = from;
to_next = to;
if(r == std::codecvt_base::ok && from != from_end)
r = std::codecvt_base::partial;
return r;
}
std::codecvt_base::result do_out(std::mbstate_t& /*std_state*/,
const uchar* from,
const uchar* from_end,
const uchar*& from_next,
char* to,
char* to_end,
char*& to_next) const override
{
std::codecvt_base::result r = std::codecvt_base::ok;
auto cvt_state = implementation().initial_state(from_unicode_state);
while(to < to_end && from < from_end) {
const std::uint32_t ch = *from;
if(!boost::locale::utf::is_valid_codepoint(ch)) {
r = std::codecvt_base::error;
break;
}
const utf::code_point len = implementation().from_unicode(cvt_state, ch, to, to_end);
if(len == boost::locale::utf::incomplete) {
r = std::codecvt_base::partial;
break;
} else if(len == boost::locale::utf::illegal) {
r = std::codecvt_base::error;
break;
}
to += len;
from++;
}
from_next = from;
to_next = to;
if(r == std::codecvt_base::ok && from != from_end)
r = std::codecvt_base::partial;
return r;
}
};
template<typename CodecvtImpl>
class generic_codecvt<char, CodecvtImpl, 1> : public std::codecvt<char, char, std::mbstate_t>,
public generic_codecvt_base {
public:
typedef char uchar;
const CodecvtImpl& implementation() const { return *static_cast<const CodecvtImpl*>(this); }
generic_codecvt(size_t refs = 0) : std::codecvt<char, char, std::mbstate_t>(refs) {}
};
}} // namespace boost::locale
#endif