disk-utils/llseek.c

   1 /*
   2  * llseek.c -- stub calling the llseek system call
   3  *
   4  * Copyright (C) 1994 Remy Card.  This file may be redistributed
   5  * under the terms of the GNU Public License.
   6  */
   7
   8 #define FOR_UTIL_LINUX
   9
  10 #include <sys/types.h>
  11
  12 #include <errno.h>
  13 #include <unistd.h>
  14
  15 #ifndef FOR_UTIL_LINUX
  16
  17 #include "et/com_err.h"
  18 #include "ext2fs/io.h"
  19
  20 #else /* FOR_UTIL_LINUX */
  21
  22 #if defined(__GNUC__) || defined(HAS_LONG_LONG)
  23 typedef long long       ext2_loff_t;
  24 #else
  25 typedef long            ext2_loff_t;
  26 #endif
  27
  28 ext2_loff_t ext2_llseek (unsigned int, ext2_loff_t, unsigned int);
  29
  30 #endif /* FOR_UTIL_LINUX */
  31
  32 #ifdef __linux__
  33
  34 #ifdef HAVE_LLSEEK
  35 #include <syscall.h>
  36
  37 #else   /* HAVE_LLSEEK */
  38
  39 #ifdef __alpha__
  40
  41 #define my_llseek lseek
  42
  43 #elif __i386__
  44
  45 #include <linux/unistd.h>
  46
  47 #ifndef __NR__llseek
  48 #define __NR__llseek            140
  49 #endif
  50
  51 static int _llseek (unsigned int, unsigned long,
  52                    unsigned long, ext2_loff_t *, unsigned int);
  53
  54 static _syscall5(int,_llseek,unsigned int,fd,unsigned long,offset_high,
  55                  unsigned long, offset_low,ext2_loff_t *,result,
  56                  unsigned int, origin)
  57
  58 static ext2_loff_t my_llseek (unsigned int fd, ext2_loff_t offset,
  59                 unsigned int origin)
  60 {
  61         ext2_loff_t result;
  62         int retval;
  63
  64         retval = _llseek (fd, ((unsigned long long) offset) >> 32,
  65                         ((unsigned long long) offset) & 0xffffffff,
  66                         &result, origin);
  67         return (retval == -1 ? (ext2_loff_t) retval : result);
  68 }
  69
  70 #else
  71
  72 #error "llseek() is not available"
  73
  74 #endif /* __alpha__ */
  75
  76 #endif  /* HAVE_LLSEEK */
  77
  78 ext2_loff_t ext2_llseek (unsigned int fd, ext2_loff_t offset,
  79                          unsigned int origin)
  80 {
  81         ext2_loff_t result;
  82         static int do_compat = 0;
  83
  84         if ((sizeof(off_t) >= sizeof(ext2_loff_t)) ||
  85             (offset < ((ext2_loff_t) 1 << ((sizeof(off_t)*8) -1))))
  86                 return lseek(fd, (off_t) offset, origin);
  87
  88         if (do_compat) {
  89                 errno = EINVAL;
  90                 return -1;
  91         }
  92
  93         result = my_llseek (fd, offset, origin);
  94         if (result == -1 && errno == ENOSYS) {
  95                 /*
  96                  * Just in case this code runs on top of an old kernel
  97                  * which does not support the llseek system call
  98                  */
  99                 do_compat++;
 100                 errno = EINVAL;
 101         }
 102         return result;
 103 }
 104
 105 #else /* !linux */
 106
 107 ext2_loff_t ext2_llseek (unsigned int fd, ext2_loff_t offset,
 108                          unsigned int origin)
 109 {
 110         if ((sizeof(off_t) < sizeof(ext2_loff_t)) &&
 111             (offset >= ((ext2_loff_t) 1 << ((sizeof(off_t)*8) -1)))) {
 112                 errno = EINVAL;
 113                 return -1;
 114         }
 115         return lseek (fd, (off_t) offset, origin);
 116 }
 117
 118 #endif  /* linux */
 119
 120