UNIX 7th Ed. - /usr/src/libc/stdio/fseek.c

   1: /*
   2:  * Seek for standard library.  Coordinates with buffering.
   3:  */
   4: 
   5: #include    <stdio.h>
   6: 
   7: long lseek();
   8: 
   9: fseek(iop, offset, ptrname)
  10:     register FILE *iop;
  11:     long offset;
  12: {
  13:     register int c;
  14:     long p;
  15: 
  16:     iop->_flag &= ~_IOEOF;
  17:     if (iop->_flag & _IOREAD) {
  18:         if (ptrname < 2 && iop->_base && !(iop->_flag&_IONBF)) {
  19:             c = iop->_cnt;
  20:             p = offset;
  21:             if (ptrname == 0)
  22:                 p += c - lseek(fileno(iop), 0L, 1);
  23:             else
  24:                 offset -= c;
  25:             if (!(iop->_flag&_IORW) && c > 0 && p <= c
  26:                 && p >= iop->_base - iop->_ptr){
  27:                 iop->_ptr += (int) p;
  28:                 iop->_cnt -= (int) p;
  29:                 return(0);
  30:             }
  31:         }
  32:         if (iop->_flag & _IORW) {
  33:             iop->_ptr = iop->_base;
  34:             iop->_flag &= ~_IOREAD;
  35:         }
  36:         p = lseek(fileno(iop), offset, ptrname);
  37:         iop->_cnt = 0;
  38:     } else if(iop->_flag & (_IOWRT|_IORW)) {
  39:         fflush(iop);
  40:         if (iop->_flag & _IORW) {
  41:             iop->_cnt = 0;
  42:             iop->_flag &= ~_IOWRT;
  43:             iop->_ptr = iop->_base;
  44:         }
  45:         p = lseek(fileno(iop), offset, ptrname);
  46:     }
  47:     return(p==-1? -1: 0);
  48: }

Defined functions