1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
|
/* Copyright (C) 2000 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#include "mysys_priv.h"
#include "mysys_err.h"
/*
Seek to a position in a file.
ARGUMENTS
File fd The file descriptor
my_off_t pos The expected position (absolute or relative)
int whence A direction parameter and one of
{SEEK_SET, SEEK_CUR, SEEK_END}
myf MyFlags MY_THREADSAFE must be set in case my_seek may be mixed
with my_pread/my_pwrite calls and fd is shared among
threads.
DESCRIPTION
The my_seek function is a wrapper around the system call lseek and
repositions the offset of the file descriptor fd to the argument
offset according to the directive whence as follows:
SEEK_SET The offset is set to offset bytes.
SEEK_CUR The offset is set to its current location plus offset bytes
SEEK_END The offset is set to the size of the file plus offset bytes
RETURN VALUE
my_off_t newpos The new position in the file.
MY_FILEPOS_ERROR An error was encountered while performing
the seek. my_errno is set to indicate the
actual error.
*/
my_off_t my_seek(File fd, my_off_t pos, int whence, myf MyFlags)
{
reg1 os_off_t newpos= -1;
DBUG_ENTER("my_seek");
DBUG_PRINT("my",("fd: %d Hpos: %lu Pos: %lu Whence: %d MyFlags: %d",
fd, (ulong) (((ulonglong) pos) >> 32), (ulong) pos,
whence, MyFlags));
DBUG_ASSERT(pos != MY_FILEPOS_ERROR); /* safety check */
/*
Make sure we are using a valid file descriptor!
*/
DBUG_ASSERT(fd != -1);
#if defined(THREAD) && !defined(HAVE_PREAD)
if (MyFlags & MY_THREADSAFE)
{
pthread_mutex_lock(&my_file_info[fd].mutex);
newpos= lseek(fd, pos, whence);
pthread_mutex_unlock(&my_file_info[fd].mutex);
}
else
#endif
newpos= lseek(fd, pos, whence);
if (newpos == (os_off_t) -1)
{
my_errno= errno;
if (MyFlags & MY_WME)
my_error(EE_CANT_SEEK, MYF(0), my_filename(fd), my_errno);
DBUG_PRINT("error",("lseek: %lu errno: %d", (ulong) newpos,errno));
DBUG_RETURN(MY_FILEPOS_ERROR);
}
if ((my_off_t) newpos != pos)
{
DBUG_PRINT("exit",("pos: %lu", (ulong) newpos));
}
DBUG_RETURN((my_off_t) newpos);
} /* my_seek */
/* Tell current position of file */
/* ARGSUSED */
my_off_t my_tell(File fd, myf MyFlags)
{
os_off_t pos;
DBUG_ENTER("my_tell");
DBUG_PRINT("my",("fd: %d MyFlags: %d",fd, MyFlags));
DBUG_ASSERT(fd >= 0);
#ifdef HAVE_TELL
pos=tell(fd);
#else
pos=lseek(fd, 0L, MY_SEEK_CUR);
#endif
if (pos == (os_off_t) -1)
{
my_errno= errno;
if (MyFlags & MY_WME)
my_error(EE_CANT_SEEK, MYF(0), my_filename(fd), my_errno);
DBUG_PRINT("error", ("tell: %lu errno: %d", (ulong) pos, my_errno));
}
DBUG_PRINT("exit",("pos: %lu", (ulong) pos));
DBUG_RETURN((my_off_t) pos);
} /* my_tell */
|
