std::mbrtoc32
Defined in header <cuchar> | ||
std::size_t mbrtoc32(char32_t* pc32, constchar* s, | (since C++11) | |
Converts a narrow multibyte character to its UTF-32 character representation.
If s is not a null pointer, inspects at most n bytes of the multibyte character string, beginning with the byte pointed to by s to determine the number of bytes necessary to complete the next multibyte character (including any shift sequences). If the function determines that the next multibyte character in s is complete and valid, converts it to the corresponding 32-bit character and stores it in *pc32 (if pc32 is not null).
If the multibyte character in *s corresponds to a multi-char32_t sequence (not possible with UTF-32), then after the first call to this function, *ps is updated in such a way that the next calls to mbrtoc32 will write out the additional char32_t, without considering *s.
If s is a null pointer, the values of n and pc32 are ignored and the call is equivalent to std::mbrtoc32(nullptr, "", 1, ps).
If the wide character produced is the null character, the conversion state *ps represents the initial shift state.
The multibyte encoding used by this function is specified by the currently active C locale.
Contents |
[edit]Parameters
| pc32 | - | pointer to the location where the resulting 32-bit character will be written |
| s | - | pointer to the multibyte character string used as input |
| n | - | limit on the number of bytes in s that can be examined |
| ps | - | pointer to the conversion state object used when interpreting the multibyte string |
[edit]Return value
The first of the following that applies:
- 0 if the character converted from s (and stored in *pc32 if non-null) was the null character.
- the number of bytes [1...n] of the multibyte character successfully converted from s.
- -3 if the next char32_t from a multi-char32_t character has now been written to *pc32. No bytes are processed from the input in this case.
- -2 if the next n bytes constitute an incomplete, but so far valid, multibyte character. Nothing is written to *pc32.
- -1 if encoding error occurs. Nothing is written to *pc32, the value EILSEQ is stored in errno and the value of *ps is unspecified.
[edit]Examples
#include <cassert>#include <clocale>#include <cstring>#include <cuchar>#include <cwchar>#include <iomanip>#include <iostream> int main(){std::setlocale(LC_ALL, "en_US.utf8"); std::string str ="z\u00df\u6c34\U0001F34C";// or u8"zß水🍌" std::cout<<"Processing "<< str.size()<<" bytes: [ "<<std::showbase;for(unsignedchar c : str)std::cout<<std::hex<<+c <<' ';std::cout<<"]\n"; std::mbstate_t state{};// zero-initialized to initial statechar32_t c32;constchar* ptr = str.c_str(), *end = str.c_str()+ str.size()+1; while(std::size_t rc = std::mbrtoc32(&c32, ptr, end - ptr, &state)){std::cout<<"Next UTF-32 char: "<<std::hex<<static_cast<int>(c32)<<" obtained from ";assert(rc !=(std::size_t)-3);// no surrogates in UTF-32if(rc ==(std::size_t)-1)break;if(rc ==(std::size_t)-2)break;std::cout<<std::dec<< rc <<" bytes [ ";for(std::size_t n =0; n < rc;++n)std::cout<<std::hex<<+static_cast<unsignedchar>(ptr[n])<<' ';std::cout<<"]\n"; ptr += rc;}}
Output:
Processing 10 bytes: [ 0x7a 0xc3 0x9f 0xe6 0xb0 0xb4 0xf0 0x9f 0x8d 0x8c ] Next UTF-32 char: 0x7a obtained from 1 bytes [ 0x7a ] Next UTF-32 char: 0xdf obtained from 2 bytes [ 0xc3 0x9f ] Next UTF-32 char: 0x6c34 obtained from 3 bytes [ 0xe6 0xb0 0xb4 ] Next UTF-32 char: 0x1f34c obtained from 4 bytes [ 0xf0 0x9f 0x8d 0x8c ]
[edit]See also
(C++11) | converts a UTF-32 character to narrow multibyte encoding (function) |
[virtual] | converts a string from ExternT to InternT, such as when reading from file (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) |
C documentation for mbrtoc32 | |
