wctob

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Date and time utilities

Strings library

Algorithms

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Input/output support

Localization support

Atomic operations (C11)

Thread support (C11)

Technical Specifications

Strings library

Byte strings

Multibyte strings

Wide strings

Null-terminated multibyte strings

Wide/multibyte conversions
mbsinit (C95)
mbtowc mbstowcsmbstowcs_s (C11) btowc (C95) mbrtowc (C95) mbsrtowcsmbsrtowcs_s (C95)(C11) mbrtoc16 (C11) c16rtomb (C11) c32rtomb (C11) mbrtoc32 (C11)	mblen wctombwctomb_s (C11) wcstombswcstombs_s (C11) wctob (C95) wcrtombwcrtomb_s (C95)(C11) wcsrtombswcsrtombs_s (C95)(C11) mbrlen (C95)
Types
mbstate_t (C95)

Defined in header <wchar.h>
int wctob( wint_t c );		(since C95)

Narrows a wide character c if its multibyte character equivalent in the initial shift state is a single byte.

This is typically possible for the characters from the ASCII character set, since most multibyte encodings (such as UTF-8) use single bytes to encode those characters.

Parameters

c

-

wide character to narrow

Return value

EOF if c does not represent a multibyte character with length 1 in initial shift state.

otherwise, the single-byte representation of c as unsigned char converted to int

Example

Run this code

#include <locale.h>
#include <wchar.h>
#include <stdio.h>
#include <assert.h>

void try_narrowing(wchar_t c)
{
    int cn = wctob(c);
    if(cn != EOF)
        printf("%#x narrowed to%#x\n", c, cn);
    else
        printf("%#x could not be narrowed\n", c);
}

int main(void)
{
    char* utf_locale_present = setlocale(LC_ALL, "th_TH.utf8");
    assert(utf_locale_present);
    puts("In Thai UTF-8 locale:");
    try_narrowing(L'a');
    try_narrowing(L'');

    char* tis_locale_present = setlocale(LC_ALL, "th_TH.tis620");
    assert(tis_locale_present);
    puts("In Thai TIS-620 locale:");
    try_narrowing(L'a');
    try_narrowing(L'');
}

Possible output:

In Thai UTF-8 locale:
0x61 narrowed to 0x61
0xe5b could not be narrowed
In Thai TIS-620 locale:
0x61 narrowed to 0x61
0xe5b narrowed to 0xfb

References

• C11 standard (ISO/IEC 9899:2011):

• 7.29.6.1.2 The wctob function (p: 441)

• C99 standard (ISO/IEC 9899:1999):

• 7.24.6.1.2 The wctob function (p: 387)

See also

btowc (C95)

widens a single-byte narrow character to wide character, if possible (function)