third_party/ulib/musl/src/stdio/fgets.c

#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);