BSD 4 development

[unix-history] / usr / src / libc / stdio / fseek.c

/*
* Seek for standard library.  Coordinates with buffering.
*/

#include        <stdio.h>

long lseek();

fseek(iop, offset, ptrname)
FILE *iop;
long offset;
{
       register resync, c;
       long p;

       iop->_flag &= ~_IOEOF;
       if (iop->_flag&_IOREAD) {
               if (ptrname<2 && iop->_base &&
                       !(iop->_flag&_IONBF)) {
                       c = iop->_cnt;
                       p = offset;
                       if (ptrname==0)
                               p += c - lseek(fileno(iop),0L,1);
                       else
                               offset -= c;
                       if(c>0&&p<=c&&p>=iop->_base-iop->_ptr){
                               iop->_ptr += (int)p;
                               iop->_cnt -= (int)p;
                               return(0);
                       }
                       resync = offset&01;
               } else 
                       resync = 0;
               p = lseek(fileno(iop), offset-resync, ptrname);
               iop->_cnt = 0;
               if (resync)
                       getc(iop);
       }
       else if (iop->_flag&_IOWRT) {
               fflush(iop);
               p = lseek(fileno(iop), offset, ptrname);
       }
       return(p==-1?-1:0);
}