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DESCRIPTION

mbrlen() is equivalent to the following call (except ps is evaluated only once):

mbrtowc(NULL, s, n, (ps != NULL) ? ps : &internal);

Here, internal is an internal state object.

In state-dependent encodings, s may point to the special sequence bytes to change the shift-state. Although such sequence bytes corresponds to no individual wide-character code, these affect the conversion state object pointed to by ps, and the mbrlen() treats the special sequence bytes as if these are a part of the subsequent multibyte character.

Unlike mblen(3), mbrlen() may accept the byte sequence when it is not a complete character but possibly contains part of a valid character. In this case, this function will accept all such bytes and save them into the conversion state object pointed to by ps. They will be used on subsequent calls of this function to restart the conversion suspended.

The behaviour of the mbrlen() is affected by LC_CTYPE category of the current locale.

There are the special cases:

s == NULL

mbrlen() sets the conversion state object pointed to by ps to an initial state and always returns 0. Unlike mblen(3), the value returned does not indicate whether the current encoding of the locale is state-dependent.

In this case, mbrlen() ignores n.

n == 0

In this case, the first n bytes of the array pointed to by s never form a complete character. Thus, mbrlen() always returns (size_t)-2.

ps == NULL

mbrlen() uses its own internal state object to keep the conversion state, instead of ps mentioned in this manual page.

Calling any other functions in libc never change the internal state of mbrlen(), except for calling setlocale(3) with a changing LC_CTYPE category of the current locale. Such setlocale(3) calls cause the internal state of this function to be indeterminate. This internal state is initialized at startup time of the program.