1 /*
2 Copyright (c) 2000, 2010, Oracle and/or its affiliates
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; version 2 of the License.
7
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
12
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
16
17 #include "mysys_priv.h"
18 #include "mysys_err.h"
19
20 /*
21 Seek to a position in a file.
22
23 ARGUMENTS
24 File fd The file descriptor
25 my_off_t pos The expected position (absolute or relative)
26 int whence A direction parameter and one of
27 {SEEK_SET, SEEK_CUR, SEEK_END}
28 myf MyFlags MY_THREADSAFE must be set in case my_seek may be mixed
29 with my_pread/my_pwrite calls and fd is shared among
30 threads.
31
32 DESCRIPTION
33 The my_seek function is a wrapper around the system call lseek and
34 repositions the offset of the file descriptor fd to the argument
35 offset according to the directive whence as follows:
36 SEEK_SET The offset is set to offset bytes.
37 SEEK_CUR The offset is set to its current location plus offset bytes
38 SEEK_END The offset is set to the size of the file plus offset bytes
39
40 RETURN VALUE
41 my_off_t newpos The new position in the file.
42 MY_FILEPOS_ERROR An error was encountered while performing
43 the seek. my_errno is set to indicate the
44 actual error.
45 */
46
my_seek(File fd,my_off_t pos,int whence,myf MyFlags)47 my_off_t my_seek(File fd, my_off_t pos, int whence, myf MyFlags)
48 {
49 os_off_t newpos= -1;
50 DBUG_ENTER("my_seek");
51 DBUG_PRINT("my",("fd: %d Pos: %llu Whence: %d MyFlags: %lu",
52 fd, (ulonglong) pos, whence, MyFlags));
53 DBUG_ASSERT(pos != MY_FILEPOS_ERROR); /* safety check */
54
55 /*
56 Make sure we are using a valid file descriptor!
57 */
58 DBUG_ASSERT(fd != -1);
59 #ifdef _WIN32
60 newpos= my_win_lseek(fd, pos, whence);
61 #else
62 newpos= lseek(fd, pos, whence);
63 #endif
64 if (newpos == (os_off_t) -1)
65 {
66 my_errno= errno;
67 if (MyFlags & MY_WME)
68 my_error(EE_CANT_SEEK, MYF(0), my_filename(fd), my_errno);
69 DBUG_PRINT("error", ("lseek: %llu errno: %d", (ulonglong) newpos, errno));
70 DBUG_RETURN(MY_FILEPOS_ERROR);
71 }
72 if ((my_off_t) newpos != pos)
73 {
74 DBUG_PRINT("exit",("pos: %llu", (ulonglong) newpos));
75 }
76 DBUG_RETURN((my_off_t) newpos);
77 } /* my_seek */
78
79
80 /* Tell current position of file */
81 /* ARGSUSED */
82
my_tell(File fd,myf MyFlags)83 my_off_t my_tell(File fd, myf MyFlags)
84 {
85 os_off_t pos;
86 DBUG_ENTER("my_tell");
87 DBUG_PRINT("my",("fd: %d MyFlags: %lu",fd, MyFlags));
88 DBUG_ASSERT(fd >= 0);
89 #if defined (HAVE_TELL) && !defined (_WIN32) && !defined(_AIX)
90 pos= tell(fd);
91 #else
92 pos= my_seek(fd, 0L, MY_SEEK_CUR,0);
93 #endif
94 if (pos == (os_off_t) -1)
95 {
96 my_errno= errno;
97 if (MyFlags & MY_WME)
98 my_error(EE_CANT_SEEK, MYF(0), my_filename(fd), my_errno);
99 DBUG_PRINT("error", ("tell: %llu errno: %d", (ulonglong) pos, my_errno));
100 }
101 DBUG_PRINT("exit",("pos: %llu", (ulonglong) pos));
102 DBUG_RETURN((my_off_t) pos);
103 } /* my_tell */
104