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man pages section 3: Basic Library Functions

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Updated: Thursday, June 13, 2019
 
 

mbsrtowcs_s(3C)

Name

mbsrtowcs, mbsnrtowcs - convert a character string to a wide-character string (restartable)

mbsrtowcs_s - wide-character string operations with additional safety checks

Synopsis

#include <wchar.h>

size_t mbsrtowcs(wchar_t *restrict dst, const char **restrict src,
     size_t len, mbstate_t *restrict ps);
size_t mbsnrtowcs(wchar_t *restrict dst, const char **restrict src,
     size_t nmc, size_t len, mbstate_t *restrict ps);
#define __STDC_WANT_LIB_EXT1__ 1
#include <wchar.h>

errno_t mbsrtowcs_s(size_t *restrict retval, wchar_t *restrict dst,
     rsize_t dstmax, const char **restrict src, rsize_t len,
     mbstate_t *restrict ps);

Description

The mbsrtowcs() function converts a sequence of characters, beginning in the conversion state described by the object pointed to by ps, from the array indirectly pointed to by src into a sequence of corresponding wide-characters. If dst is not a null pointer, the converted characters are stored into the array pointed to by dst. Conversion continues up to and including a terminating null character, which is also stored. Conversion stops early in either of the following cases:

  • When a sequence of bytes is encountered that does not form a valid character.

  • When len codes have been stored into the array pointed to by dst (and dst is not a null pointer).

Each conversion takes place as if by a call to the mbrtowc() function.

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

If ps is a null pointer, the mbsrtowcs() function uses its own internal mbstate_t object, which is initialized at program startup to the initial conversion state. Otherwise, the mbstate_t object pointed to by ps is used to completely describe the current conversion state of the associated character sequence. Solaris will behave as if no function defined in the Solaris Reference Manual calls these functions.

The mbsnrtowcs() function is equivalent to the mbsrtowcs() function, except that the conversion of characters pointed to by src is limited to at most nmc bytes (the size of the input buffer).

The behavior of these functions are affected by the LC_CTYPE category of the current locale. See environ(7).

The mbsrtowcs_s() function is part of the bounds checking interfaces specified in the C11 standard, Annex K. It is similar to mbsrtowcs() in that it converts a sequence of multibyte characters into a sequence of corresponding wide characters, but with additional safety checks for explicit runtime constraints as defined by the C11 standard. See runtime_constraint_handler(3C) and INCITS/ISO/IEC 9899:2011.

Return Values

If the input conversion encounters a sequence of bytes that do not form a valid character, an encoding error occurs. In this case, these functions store the value of the macro EILSEQ in errno and returns (size_t)-1; the conversion state is undefined. Otherwise, it returns the number of characters successfully converted, not including the terminating null (if any).

Additionally, if there is no runtime-constraint violation, the mbsrtowcs_s() function returns zero. Otherwise, it returns a non-zero value.

Errors

The mbsrtowcs() function will fail if:

EINVAL

The ps argument points to an object that contains an invalid conversion state.

EILSEQ

Invalid character sequence is detected.

The mbsrtowcs_s() function will fail if:

EINVAL

Null pointer is passed or source and destination overlaps.

ERANGE

size argument is not a valid value.

EOVERFLOW

Destination array is too small.

EILSEQ

Illegal byte sequence.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
See NOTES below
Standard

See Also

mbrtowc(3C), mbsinit(3C), setlocale(3C), attributes(7), environ(7), standards(7)

Notes

If ps is not a null pointer, mbsrtowcs() and mbsnrtowcs() use the xmbstate_t object pointed to by ps and the functions can be used safely in multithreaded applications. If ps is a null pointer, mbsrtowcs() and mbsnrtowcs() use their internal mbstate_t object and the function is Unsafe in multithreaded applications.

The mbsrtowcs() function can be used safely in multithreaded applications.

The mbsrtowcs_s() function cannot be used safely in a multithreaded application due to the runtime constraint handler. For more information, see the runtime_constraint_handler(3C) man page.