github.com/afumu/libc@v0.0.6/musl/src/stdio/fgets.c (about)

     1  #include "stdio_impl.h"
     2  #include <string.h>
     3  
     4  #define MIN(a,b) ((a)<(b) ? (a) : (b))
     5  
     6  char *fgets(char *restrict s, int n, FILE *restrict f)
     7  {
     8  	char *p = s;
     9  	unsigned char *z;
    10  	size_t k;
    11  	int c;
    12  
    13  	FLOCK(f);
    14  
    15  	if (n--<=1) {
    16  		f->mode |= f->mode-1;
    17  		FUNLOCK(f);
    18  		if (n) return 0;
    19  		*s = 0;
    20  		return s;
    21  	}
    22  
    23  	while (n) {
    24  		if (f->rpos != f->rend) {
    25  			z = memchr(f->rpos, '\n', f->rend - f->rpos);
    26  			k = z ? z - f->rpos + 1 : f->rend - f->rpos;
    27  			k = MIN(k, n);
    28  			memcpy(p, f->rpos, k);
    29  			f->rpos += k;
    30  			p += k;
    31  			n -= k;
    32  			if (z || !n) break;
    33  		}
    34  		if ((c = getc_unlocked(f)) < 0) {
    35  			if (p==s || !feof(f)) s = 0;
    36  			break;
    37  		}
    38  		n--;
    39  		if ((*p++ = c) == '\n') break;
    40  	}
    41  	if (s) *p = 0;
    42  
    43  	FUNLOCK(f);
    44  
    45  	return s;
    46  }
    47  
    48  weak_alias(fgets, fgets_unlocked);