source: azure_iot_hub/trunk/musl-1.1.18/src/stdio/fgets.c@ 388

#include "stdio_impl.h"
#include <string.h>

#define MIN(a,b) ((a)<(b) ? (a) : (b))

char *fgets(char *restrict s, int n, FILE *restrict f)
{
        char *p = s;
        unsigned char *z;
        size_t k;
        int c;

        FLOCK(f);

        if (n--<=1) {
                f->mode |= f->mode-1;
                FUNLOCK(f);
                if (n) return 0;
                *s = 0;
                return s;
        }

        while (n) {
                z = memchr(f->rpos, '\n', f->rend - f->rpos);
                k = z ? z - f->rpos + 1 : f->rend - f->rpos;
                k = MIN(k, n);
                memcpy(p, f->rpos, k);
                f->rpos += k;
                p += k;
                n -= k;
                if (z || !n) break;
                if ((c = getc_unlocked(f)) < 0) {
                        if (p==s || !feof(f)) s = 0;
                        break;
                }
                n--;
                if ((*p++ = c) == '\n') break;
        }
        if (s) *p = 0;

        FUNLOCK(f);

        return s;
}

weak_alias(fgets, fgets_unlocked);