src/stdio/fgets.c

   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);