NAME

wcsnrtombs, wcsrtombs — convert a wide-character string to a character string (restartable)

SYNOPSIS

#include <wchar.h>



[CX] size_t wcsnrtombs(char *restrict dst, const wchar_t **restrict src,
       size_t nwc, size_t len, mbstate_t *restrict ps);

size_t wcsrtombs(char *restrict dst, const wchar_t **restrict src,
       size_t len, mbstate_t *restrict ps);

DESCRIPTION

For wcsrtombs(): ^[CX]  The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.

The wcsrtombs() function shall convert a sequence of wide characters from the array indirectly pointed to by src into a sequence of corresponding characters, beginning in the conversion state described by the object pointed to by ps. If dst is not a null pointer, the converted characters shall then be stored into the array pointed to by dst. Conversion continues up to and including a terminating null wide character, which shall also be stored. Conversion shall stop earlier in the following cases:

• When a code is reached that does not correspond to a valid character

• When the next character would exceed the limit of len total bytes to be stored in the array pointed to by dst (and dst is not a null pointer)

Each conversion shall take place as if by a call to the wcrtomb() function.

If dst is not a null pointer, the pointer object pointed to by src shall be assigned either a null pointer (if conversion stopped due to reaching a terminating null wide character) or the address just past the last wide character converted (if any). If conversion stopped due to reaching a terminating null wide character, the resulting state described shall be the initial conversion state.

If ps is a null pointer, the wcsrtombs() function shall use its own internal mbstate_t object, which is initialized at program start-up to the initial conversion state. Otherwise, the mbstate_t object pointed to by ps shall be used to completely describe the current conversion state of the associated character sequence.

If called with a null ps argument, the wcsrtombs() function need not be thread-safe; however, such calls shall avoid data races with calls to wcsrtombs() with a non-null argument and with calls to all other functions.

^[CX] The wcsnrtombs() function shall be equivalent to the wcsrtombs() function, except that the conversion is limited to the first nwc wide characters.

If called with a null ps argument, the wcsnrtombs() function need not be thread-safe; however, such calls shall avoid data races with calls to wcsnrtombs() with a non-null argument and with calls to all other functions.

These functions shall not change the setting of errno if successful.

The behavior of these functions shall be affected by the LC_CTYPE category of the current locale.

The implementation shall behave as if no function defined in System Interfaces volume of POSIX.1-2024 calls these functions.

RETURN VALUE

If conversion stops because a code is reached that does not correspond to a valid character, an encoding error occurs. In this case, these functions shall store the value of the macro [EILSEQ] in errno and return (size_t)-1; the conversion state is undefined. Otherwise, these functions shall return the number of bytes in the resulting character sequence, not including the terminating null (if any).

ERRORS

These functions shall fail if:

[EILSEQ]

A wide-character code does not correspond to a valid character.

These functions may fail if:

[EINVAL]

^[CX] ps points to an object that contains an invalid conversion state.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

mbsinit, wcrtomb

XBD <wchar.h>

CHANGE HISTORY

First released in Issue 5. Included for alignment with ISO/IEC 9899:1990/Amendment 1:1995 (E).

Issue 6

In the DESCRIPTION, a note on using this function in a threaded application is added.

Extensions beyond the ISO C standard are marked.

The normative text is updated to avoid use of the term "must" for application requirements.

The wcsrtombs() prototype is updated for alignment with the ISO/IEC 9899:1999 standard.

Issue 7

Austin Group Interpretation 1003.1-2001 #148 is applied, clarifying that the wcsrtombs() function need not be thread-safe if called with a NULL ps argument.

Austin Group Interpretation 1003.1-2001 #170 is applied.

The wcsnrtombs() function is added from The Open Group Technical Standard, 2006, Extended API Set Part 1.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0722 [109,105] is applied.

Issue 8

Austin Group Defect 1302 is applied, aligning these functions with the ISO/IEC 9899:2018 standard.