osdep/fseeko.c

   1 /*
   2  * fseeko.c
   3  *        64-bit versions of fseeko/ftello() for systems which do not have them
   4  */
   5
   6 #include "config.h"
   7
   8 #include <stdio.h>
   9 #include <sys/types.h>
  10 #include <sys/stat.h>
  11 #include <errno.h>
  12
  13 #ifdef WIN32
  14 #define flockfile
  15 #define funlockfile
  16 #endif
  17
  18 /*
  19  *      On BSD/OS and NetBSD (and perhaps others), off_t and fpos_t are the
  20  *      same.  Standards say off_t is an arithmetic type, but not necessarily
  21  *      integral, while fpos_t might be neither.
  22  *
  23  *      This is thread-safe on BSD/OS using flockfile/funlockfile.
  24  */
  25
  26 int
  27 fseeko(FILE *stream, off_t offset, int whence)
  28 {
  29         fpos_t floc;
  30         struct stat filestat;
  31
  32         switch (whence)
  33         {
  34                 case SEEK_CUR:
  35                         flockfile(stream);
  36                         if (fgetpos(stream, &floc) != 0)
  37                                 goto failure;
  38                         floc += offset;
  39                         if (fsetpos(stream, &floc) != 0)
  40                                 goto failure;
  41                         funlockfile(stream);
  42                         return 0;
  43                         break;
  44                 case SEEK_SET:
  45                         if (fsetpos(stream, &offset) != 0)
  46                                 return -1;
  47                         return 0;
  48                         break;
  49                 case SEEK_END:
  50                         flockfile(stream);
  51                         if (fstat(fileno(stream), &filestat) != 0)
  52                                 goto failure;
  53                         floc = filestat.st_size;
  54                         if (fsetpos(stream, &floc) != 0)
  55                                 goto failure;
  56                         funlockfile(stream);
  57                         return 0;
  58                         break;
  59                 default:
  60                         errno = EINVAL;
  61                         return -1;
  62         }
  63
  64 failure:
  65         funlockfile(stream);
  66         return -1;
  67 }