1) Converts a sequence of wide characters from the array whose first element is pointed to by src to its narrow multibyte representation that begins in the initial shift state. Converted characters are stored in the successive elements of the char array pointed to by dst. No more than len bytes are written to the destination array.
Each character is converted as if by a call to
wctomb, except that the wctomb's conversion state is unaffected. The conversion stops if:
* The null character L'\0' was converted and stored. The bytes stored in this case are the unshift sequence (if necessary) followed by '\0',
* A wchar_t was found that does not correspond to a valid character in the current C locale.
* The next multibyte character to be stored would exceed len.
If src and dst overlap, the behavior is unspecified.
2) Same as (1), except that
* the function returns its result as an out-parameter retval
* if the conversion stops without writing a null character, the function will store '\0' in the next byte in dst, which may be dst[len] or dst[dstsz], whichever comes first (meaning up to len+1/dstsz+1 total bytes may be written). In this case, there may be no unshift sequence written before the terminating null.
* if dst is a null pointer, the number of bytes that would be produced is stored in *retval
* the function clobbers the destination array from the terminating null and until dstsz
* If src and dst overlap, the behavior is unspecified.
* the following errors are detected at runtime and call the currently installed
constraint handlerfunction:
retval or src is a null pointerdstsz or len is greater than RSIZE_MAX (unless dst is null)dstsz is not zero (unless dst is null)len is greater than dstsz and the conversion does not encounter null or encoding error in the src array by the time dstsz is reached (unless dst is null)wcstombs_s is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including <stdlib.h>.
In most implementations, wcstombs updates a global static object of type mbstate_t as it processes through the string, and cannot be called simultaneously by two threads, wcsrtombs or wcstombs_s should be used in such cases.
POSIX specifies a common extension: if dst is a null pointer, this function returns the number of bytes that would be written to dst, if converted. Similar behavior is standard for wcsrtombs and wcstombs_s.
dst array) retval - pointer to a size_t object where the result will be stored [edit] Return value 1)
On success, returns the number of bytes (including any shift sequences, but excluding the terminating
'\0') written to the character array whose first element is pointed to by
dst
. On conversion error (if invalid wide character was encountered), returns
(size_t)-1.
2)Returns zero on success (in which case the number of bytes excluding terminating zero that were, or would be written to
dst
, is stored in
*retval), non-zero on error. In case of a runtime constraint violation, stores
(size_t)-1in
*retval(unless
retval
is null) and sets
dst[0]to
'\0'(unless
dst
is null or
dstmax
is zero or greater than
RSIZE_MAX)
[edit] Example#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
int main(void)
{
// 4 wide characters
const wchar_t src[] = L"z\u00df\u6c34\U0001f34c";
// they occupy 10 bytes in UTF-8
char dst[11];
setlocale(LC_ALL, "en_US.utf8");
printf("wide-character string: '%ls'\n",src);
for (size_t ndx=0; ndx < sizeof src/sizeof src[0]; ++ndx)
printf(" src[%2zu] = %#8x\n", ndx, src[ndx]);
int rtn_val = wcstombs(dst, src, sizeof dst);
printf("rtn_val = %d\n", rtn_val);
if (rtn_val > 0)
printf("multibyte string: '%s'\n",dst);
for (size_t ndx=0; ndx<sizeof dst; ++ndx)
printf(" dst[%2zu] = %#2x\n", ndx, (unsigned char)dst[ndx]);
}
Output:
wide-character string: 'zÃæ°´ð' src[ 0] = 0x7a src[ 1] = 0xdf src[ 2] = 0x6c34 src[ 3] = 0x1f34c src[ 4] = 0 rtn_val = 10 multibyte string: 'zÃæ°´ð' dst[ 0] = 0x7a dst[ 1] = 0xc3 dst[ 2] = 0x9f dst[ 3] = 0xe6 dst[ 4] = 0xb0 dst[ 5] = 0xb4 dst[ 6] = 0xf0 dst[ 7] = 0x9f dst[ 8] = 0x8d dst[ 9] = 0x8c dst[10] = 0[edit] References
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