BSD 4_3 release

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

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)fseek.c     5.3 (Berkeley) 3/9/86";
#endif LIBC_SCCS and not lint

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

#include        <stdio.h>

long lseek();

fseek(iop, offset, ptrname)
       register FILE *iop;
       long offset;
{
       register resync, c;
       long p = -1;                    /* can't happen? */

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