std::ctype::widen,do_widen (3) Linux Manual Page
std::ctype<CharT>::widen,do_widen – std::ctype<CharT>::widen,do_widen
Synopsis
Defined in header<locale>
public : (1)
CharT widen(char c) const;
public:
(2)
const char *widen(const char *beg, const char *end, CharT *dst) const;
protected:
(3)
virtual CharT do_widen(char c) const;
protected:
(4)
virtual const char *do_widen(const char *beg, const char *end, CharT *dst) const;1,2) public member function, calls the protected virtual member function do_widen of the most derived class.
3) Converts the single-byte character c to the corresponding wide character representation using the simplest reasonable transformation. Typically, this applies only to the characters whose multibyte encoding is a single byte (e.g. U+0000-U+007F in UTF-8).
4) For every character in the character array [beg, end), writes the corresponding widened character to the successive locations in the character array pointed to by dst.
Widening always returns a wide character, but only the characters from the basic source character set (latin letters, digits, and punctuations required to write a C++ program) are guaranteed to have a unique, well-defined, widening transformation, which is also guaranteed to be reversible (by narrow()). In practice, all characters whose multibyte representation is a single byte are usually widened to their wide character counterparts, and the rest of the possible single-byte values are usually mapped into the same placeholder value, typically CharT(-1).
Widening, if successful, preserves all character classification categories known to is().
Parameters
c – character to convert
dflt – default value to produce if the conversion fails
beg – pointer to the first character in an array of characters to convert
end – one past the end pointer for the array of characters to convert
dst – pointer to the first element of the array of char to fill
Return value
1,3) widened character
2,4) end
Example
// Run this code
#include <locale>
#include <iostream>
void try_widen(const std::ctype<wchar_t> &f, char c)
{
wchar_t w = f.widen(c);
std::cout << "The single-byte character " << +(unsigned char)c
<< " widens to " << +w << '\n';
}
int main()
{
std::locale::global(std::locale("cs_CZ.iso88592"));
auto &f = std::use_facet<std::ctype<wchar_t>>(std::locale());
std::cout << std::hex << std::showbase << "In Czech ISO-8859-2 locale:\n";
try_widen(f, 'a');
try_widen(f, '\xdf'); // German letter ß (U+00df) in ISO-8859-2
try_widen(f, '\xec'); // Czech letter ě (U+011b) in ISO-8859-2
std::locale::global(std::locale("cs_CZ.utf8"));
auto &f2 = std::use_facet<std::ctype<wchar_t>>(std::locale());
std::cout << "In Czech UTF-8 locale:\n";
try_widen(f2, 'a');
try_widen(f2, '\xdf');
try_widen(f2, '\xec');
}
Output:
See also
narrow (public member function)
widen (public member function of std::basic_ios<CharT,Traits>)
btowc (function)