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 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.
The implementation 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 compatible 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 Reference 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.
AUTHOR
mbsrtowcs()
was developed by HP and Mitsubishi Electric Corporation.
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