ext-boost/boost/detail/utf8_codecvt_facet.ipp
2022-08-26 23:24:04 +03:00

297 lines
9.2 KiB
C++

/////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
// utf8_codecvt_facet.ipp
// Copyright (c) 2001 Ronald Garcia, Indiana University (garcia@osl.iu.edu)
// Andrew Lumsdaine, Indiana University (lums@osl.iu.edu).
// Use, modification and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Please see the comments in <boost/detail/utf8_codecvt_facet.hpp> to
// learn how this file should be used.
#include <boost/detail/utf8_codecvt_facet.hpp>
#include <cstdlib> // for multi-byte converson routines
#include <cassert>
#include <boost/limits.hpp>
#include <boost/config.hpp>
// If we don't have wstring, then Unicode support
// is not available anyway, so we don't need to even
// compiler this file. This also fixes the problem
// with mingw, which can compile this file, but will
// generate link error when building DLL.
#ifndef BOOST_NO_STD_WSTRING
BOOST_UTF8_BEGIN_NAMESPACE
/////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
// implementation for wchar_t
namespace detail {
inline const wchar_t * get_octet1_modifier_table() BOOST_NOEXCEPT
{
static const wchar_t octet1_modifier_table[] = {
0x00, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc
};
return octet1_modifier_table;
}
} // namespace detail
BOOST_UTF8_DECL utf8_codecvt_facet::utf8_codecvt_facet(
std::size_t no_locale_manage
) :
std::codecvt<wchar_t, char, std::mbstate_t>(no_locale_manage)
{}
BOOST_UTF8_DECL utf8_codecvt_facet::~utf8_codecvt_facet()
{}
// Translate incoming UTF-8 into UCS-4
BOOST_UTF8_DECL std::codecvt_base::result utf8_codecvt_facet::do_in(
std::mbstate_t& /*state*/,
const char * from,
const char * from_end,
const char * & from_next,
wchar_t * to,
wchar_t * to_end,
wchar_t * & to_next
) const {
// Basic algorithm: The first octet determines how many
// octets total make up the UCS-4 character. The remaining
// "continuing octets" all begin with "10". To convert, subtract
// the amount that specifies the number of octets from the first
// octet. Subtract 0x80 (1000 0000) from each continuing octet,
// then mash the whole lot together. Note that each continuing
// octet only uses 6 bits as unique values, so only shift by
// multiples of 6 to combine.
const wchar_t * const octet1_modifier_table = detail::get_octet1_modifier_table();
while (from != from_end && to != to_end) {
// Error checking on the first octet
if (invalid_leading_octet(*from)) {
from_next = from;
to_next = to;
return std::codecvt_base::error;
}
// The first octet is adjusted by a value dependent upon
// the number of "continuing octets" encoding the character
const int cont_octet_count = get_cont_octet_count(*from);
// The unsigned char conversion is necessary in case char is
// signed (I learned this the hard way)
wchar_t ucs_result =
(unsigned char)(*from++) - octet1_modifier_table[cont_octet_count];
// Invariants:
// 1) At the start of the loop, 'i' continuing characters have been
// processed
// 2) *from points to the next continuing character to be processed.
int i = 0;
while (i != cont_octet_count && from != from_end) {
// Error checking on continuing characters
if (invalid_continuing_octet(*from)) {
from_next = from;
to_next = to;
return std::codecvt_base::error;
}
ucs_result *= (1 << 6);
// each continuing character has an extra (10xxxxxx)b attached to
// it that must be removed.
ucs_result += (unsigned char)(*from++) - 0x80;
++i;
}
// If the buffer ends with an incomplete unicode character...
if (from == from_end && i != cont_octet_count) {
// rewind "from" to before the current character translation
from_next = from - (i + 1);
to_next = to;
return std::codecvt_base::partial;
}
*to++ = ucs_result;
}
from_next = from;
to_next = to;
// Were we done converting or did we run out of destination space?
if (from == from_end)
return std::codecvt_base::ok;
else
return std::codecvt_base::partial;
}
BOOST_UTF8_DECL std::codecvt_base::result utf8_codecvt_facet::do_out(
std::mbstate_t& /*state*/,
const wchar_t * from,
const wchar_t * from_end,
const wchar_t * & from_next,
char * to,
char * to_end,
char * & to_next
) const
{
const wchar_t * const octet1_modifier_table = detail::get_octet1_modifier_table();
wchar_t max_wchar = (std::numeric_limits<wchar_t>::max)();
while (from != from_end && to != to_end) {
// Check for invalid UCS-4 character
if (*from > max_wchar) {
from_next = from;
to_next = to;
return std::codecvt_base::error;
}
int cont_octet_count = get_cont_octet_out_count(*from);
// RG - comment this formula better
int shift_exponent = cont_octet_count * 6;
// Process the first character
*to++ = static_cast<char>(octet1_modifier_table[cont_octet_count] +
(unsigned char)(*from / (1 << shift_exponent)));
// Process the continuation characters
// Invariants: At the start of the loop:
// 1) 'i' continuing octets have been generated
// 2) '*to' points to the next location to place an octet
// 3) shift_exponent is 6 more than needed for the next octet
int i = 0;
while (i != cont_octet_count && to != to_end) {
shift_exponent -= 6;
*to++ = static_cast<char>(0x80 + ((*from / (1 << shift_exponent)) % (1 << 6)));
++i;
}
// If we filled up the out buffer before encoding the character
if (to == to_end && i != cont_octet_count) {
from_next = from;
to_next = to - (i + 1);
return std::codecvt_base::partial;
}
++from;
}
from_next = from;
to_next = to;
// Were we done or did we run out of destination space
if (from == from_end)
return std::codecvt_base::ok;
else
return std::codecvt_base::partial;
}
// How many char objects can I process to get <= max_limit
// wchar_t objects?
BOOST_UTF8_DECL int utf8_codecvt_facet::do_length(
std::mbstate_t &,
const char * from,
const char * from_end,
std::size_t max_limit
) const
#if BOOST_WORKAROUND(__IBMCPP__, BOOST_TESTED_AT(600))
throw()
#endif
{
const char * from_next = from;
for (std::size_t char_count = 0u; char_count < max_limit && from_next < from_end; ++char_count) {
unsigned int octet_count = get_octet_count(*from_next);
// The buffer may represent incomplete characters, so terminate early if one is found
if (octet_count > static_cast<std::size_t>(from_end - from_next))
break;
from_next += octet_count;
}
return static_cast<int>(from_next - from);
}
BOOST_UTF8_DECL unsigned int utf8_codecvt_facet::get_octet_count(
unsigned char lead_octet
) {
// if the 0-bit (MSB) is 0, then 1 character
if (lead_octet <= 0x7f) return 1;
// Otherwise the count number of consecutive 1 bits starting at MSB
// assert(0xc0 <= lead_octet && lead_octet <= 0xfd);
if (0xc0 <= lead_octet && lead_octet <= 0xdf) return 2;
else if (0xe0 <= lead_octet && lead_octet <= 0xef) return 3;
else if (0xf0 <= lead_octet && lead_octet <= 0xf7) return 4;
else if (0xf8 <= lead_octet && lead_octet <= 0xfb) return 5;
else return 6;
}
namespace detail {
template<std::size_t s>
inline int get_cont_octet_out_count_impl(wchar_t word) {
if (word < 0x80) {
return 0;
}
if (word < 0x800) {
return 1;
}
return 2;
}
template<>
inline int get_cont_octet_out_count_impl<4>(wchar_t word) {
if (word < 0x80) {
return 0;
}
if (word < 0x800) {
return 1;
}
// Note that the following code will generate warnings on some platforms
// where wchar_t is defined as UCS2. The warnings are superfluous as the
// specialization is never instantitiated with such compilers, but this
// can cause problems if warnings are being treated as errors, so we guard
// against that. Including <boost/detail/utf8_codecvt_facet.hpp> as we do
// should be enough to get WCHAR_MAX defined.
#if !defined(WCHAR_MAX)
# error WCHAR_MAX not defined!
#endif
// cope with VC++ 7.1 or earlier having invalid WCHAR_MAX
#if defined(_MSC_VER) && _MSC_VER <= 1310 // 7.1 or earlier
return 2;
#elif WCHAR_MAX > 0x10000
if (word < 0x10000) {
return 2;
}
if (word < 0x200000) {
return 3;
}
if (word < 0x4000000) {
return 4;
}
return 5;
#else
return 2;
#endif
}
} // namespace detail
// How many "continuing octets" will be needed for this word
// == total octets - 1.
BOOST_UTF8_DECL int utf8_codecvt_facet::get_cont_octet_out_count(
wchar_t word
) {
return detail::get_cont_octet_out_count_impl<sizeof(wchar_t)>(word);
}
BOOST_UTF8_END_NAMESPACE
#endif