mbsrtowcs.3c (2010 09)

m
mbsrtowcs(3C) mbsrtowcs(3C)
NAME
mbsrtowcs( ) - convert a character string to a wide-character string (restartable)
SYNOPSIS
#include <wchar.h>
size_t mbsrtowcs(wchar_t *__restrict dst, const char **__restrict src,
size_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 from 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 conver-
sion stopped due to reaching a terminating null character) or the address just past the last character con-
verted (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 initial-
ized 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. The imple-
mentation will behave as if no function defined in this specification calls
mbsrtowcs().
APPLICATION USAGE
The prototype of this function is available to applications if they are:
a.
c99 conformant.
b. Compiled with
-D_XOPEN_SOURCE
macro with a value >=500.
c. Compiled with
-D_POSIX_C_SOURCE
macro with a value >= 200112.
EXTERNAL INFLUENCES
Environment Variables
The behavior of this function is affected by the
LC_CTYPE category of the current locale.
RETURN VALUE
If the input conversion encounters a sequence of bytes that do not form a valid character, an encoding
error occurs. In this case, the
mbsrtowcs() function stores 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).
ERRORS
The
mbsrtowcs() function may fail if:
[EILSEQ] Invalid character sequence is detected.
[EINVAL] ps points to an object that contains an invalid conversion state.
WARNINGS
With the exception of ASCII characters, the code values of wide characters (type of
wchar_t) are specific
to the effective locale specified by the LC_CTYPE environment variable. These values may not be compa-
tible with values obtained by specifying other locales that are supported now, or which may be supported
in the future. It is recommended that wide character constants and wide string literals (see the C Refer-
ence Manual ) not be used, and that wide character code values not be stored in files or devices because
future standards may dictate changes in the code value assignments of the wide characters. However,
wide character constants and wide string literals corresponding to the characters of the ASCII code set
can be safely used since their values are guaranteed to be the same as their ASCII code set values.
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