src/internal/shgetc.c

   1 #include "shgetc.h"
   2
   3 /* The shcnt field stores the number of bytes read so far, offset by
   4  * the value of buf-rpos at the last function call (__shlim or __shgetc),
   5  * so that between calls the inline shcnt macro can add rpos-buf to get
   6  * the actual count. */
   7
   8 void __shlim(FILE *f, off_t lim)
   9 {
  10         f->shlim = lim;
  11         f->shcnt = f->buf - f->rpos;
  12         /* If lim is nonzero, rend must be a valid pointer. */
  13         if (lim && f->rend - f->rpos > lim)
  14                 f->shend = f->rpos + lim;
  15         else
  16                 f->shend = f->rend;
  17 }
  18
  19 int __shgetc(FILE *f)
  20 {
  21         int c;
  22         off_t cnt = shcnt(f);
  23         if (f->shlim && cnt >= f->shlim || (c=__uflow(f)) < 0) {
  24                 f->shcnt = f->buf - f->rpos + cnt;
  25                 f->shend = f->rpos;
  26                 f->shlim = -1;
  27                 return EOF;
  28         }
  29         cnt++;
  30         if (f->shlim && f->rend - f->rpos > f->shlim - cnt)
  31                 f->shend = f->rpos + (f->shlim - cnt);
  32         else
  33                 f->shend = f->rend;
  34         f->shcnt = f->buf - f->rpos + cnt;
  35         if (f->rpos <= f->buf) f->rpos[-1] = c;
  36         return c;
  37 }