lib/libc/stdio/ftell.c

   1 /*
   2  * ftell.c - obtain the value of the file-position indicator of a stream
   3  */
   4 /* $Header$ */
   5
   6 #include        <stdio.h>
   7
   8 #if     (SEEK_CUR != 1) || (SEEK_SET != 0) || (SEEK_END != 2)
   9 #error SEEK_* values are wrong
  10 #endif
  11
  12 #include        "loc_incl.h"
  13
  14 #include        <sys/types.h>
  15
  16 off_t _lseek(int fildes, off_t offset, int whence);
  17
  18 long ftell(FILE *stream)
  19 {
  20         long result;
  21         int adjust = 0;
  22
  23         if (io_testflag(stream,_IOREADING))
  24                 adjust = -stream->_count;
  25         else if (io_testflag(stream,_IOWRITING)
  26                     && stream->_buf
  27                     && !io_testflag(stream,_IONBF))
  28                 adjust = stream->_ptr - stream->_buf;
  29         else adjust = 0;
  30
  31         result = _lseek(fileno(stream), (off_t)0, SEEK_CUR);
  32
  33         if ( result == -1 )
  34                 return result;
  35
  36         result += (long) adjust;
  37         return result;
  38 }