github.com/afumu/libc@v0.0.6/musl/src/multibyte/mbrtowc.c (about)

     1  #include <stdlib.h>
     2  #include <wchar.h>
     3  #include <errno.h>
     4  #include "internal.h"
     5  
     6  size_t mbrtowc(wchar_t *restrict wc, const char *restrict src, size_t n, mbstate_t *restrict st)
     7  {
     8  	static unsigned internal_state;
     9  	unsigned c;
    10  	const unsigned char *s = (const void *)src;
    11  	const unsigned N = n;
    12  	wchar_t dummy;
    13  
    14  	if (!st) st = (void *)&internal_state;
    15  	c = *(unsigned *)st;
    16  	
    17  	if (!s) {
    18  		if (c) goto ilseq;
    19  		return 0;
    20  	} else if (!wc) wc = &dummy;
    21  
    22  	if (!n) return -2;
    23  	if (!c) {
    24  		if (*s < 0x80) return !!(*wc = *s);
    25  		if (MB_CUR_MAX==1) return (*wc = CODEUNIT(*s)), 1;
    26  		if (*s-SA > SB-SA) goto ilseq;
    27  		c = bittab[*s++-SA]; n--;
    28  	}
    29  
    30  	if (n) {
    31  		if (OOB(c,*s)) goto ilseq;
    32  loop:
    33  		c = c<<6 | *s++-0x80; n--;
    34  		if (!(c&(1U<<31))) {
    35  			*(unsigned *)st = 0;
    36  			*wc = c;
    37  			return N-n;
    38  		}
    39  		if (n) {
    40  			if (*s-0x80u >= 0x40) goto ilseq;
    41  			goto loop;
    42  		}
    43  	}
    44  
    45  	*(unsigned *)st = c;
    46  	return -2;
    47  ilseq:
    48  	*(unsigned *)st = 0;
    49  	errno = EILSEQ;
    50  	return -1;
    51  }