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
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
// --------------------------------------------------------------------------
//
// File
// Name: NamedLock.cpp
// Purpose: A global named lock, implemented as a lock file in
// file system
// Created: 2003/08/28
//
// --------------------------------------------------------------------------
#include "Box.h"
#include <fcntl.h>
#include <errno.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_FLOCK
#include <sys/file.h>
#endif
#include "NamedLock.h"
#include "CommonException.h"
#include "MemLeakFindOn.h"
// --------------------------------------------------------------------------
//
// Function
// Name: NamedLock::NamedLock()
// Purpose: Constructor
// Created: 2003/08/28
//
// --------------------------------------------------------------------------
NamedLock::NamedLock()
: mFileDescriptor(-1)
{
}
// --------------------------------------------------------------------------
//
// Function
// Name: NamedLock::~NamedLock()
// Purpose: Destructor (automatically unlocks if locked)
// Created: 2003/08/28
//
// --------------------------------------------------------------------------
NamedLock::~NamedLock()
{
if(mFileDescriptor != -1)
{
ReleaseLock();
}
}
// --------------------------------------------------------------------------
//
// Function
// Name: NamedLock::TryAndGetLock(const char *, int)
// Purpose: Tries to get a lock on the name in the file system.
// IMPORTANT NOTE: If a file exists with this name, it
// will be deleted.
// Created: 2003/08/28
//
// --------------------------------------------------------------------------
bool NamedLock::TryAndGetLock(const char *Filename, int mode)
{
// Check
if(mFileDescriptor != -1)
{
THROW_EXCEPTION(CommonException, NamedLockAlreadyLockingSomething)
}
// See if the lock can be got
#if HAVE_DECL_O_EXLOCK
int fd = ::open(Filename, O_WRONLY | O_NONBLOCK | O_CREAT | O_TRUNC | O_EXLOCK, mode);
if(fd != -1)
{
// Got a lock, lovely
mFileDescriptor = fd;
return true;
}
// Failed. Why?
if(errno != EWOULDBLOCK)
{
// Not the expected error
THROW_EXCEPTION(CommonException, OSFileError)
}
return false;
#else
int fd = ::open(Filename, O_WRONLY | O_CREAT | O_TRUNC, mode);
if(fd == -1)
{
BOX_WARNING("Failed to open lockfile: " << Filename);
THROW_EXCEPTION(CommonException, OSFileError)
}
#ifdef HAVE_FLOCK
if(::flock(fd, LOCK_EX | LOCK_NB) != 0)
{
::close(fd);
if(errno == EWOULDBLOCK)
{
return false;
}
else
{
THROW_EXCEPTION(CommonException, OSFileError)
}
}
#elif HAVE_DECL_F_SETLK
struct flock desc;
desc.l_type = F_WRLCK;
desc.l_whence = SEEK_SET;
desc.l_start = 0;
desc.l_len = 0;
if(::fcntl(fd, F_SETLK, &desc) != 0)
{
::close(fd);
if(errno == EAGAIN)
{
return false;
}
else
{
THROW_EXCEPTION(CommonException, OSFileError)
}
}
#endif
// Success
mFileDescriptor = fd;
return true;
#endif
}
// --------------------------------------------------------------------------
//
// Function
// Name: NamedLock::ReleaseLock()
// Purpose: Release the lock. Exceptions if the lock is not held
// Created: 2003/08/28
//
// --------------------------------------------------------------------------
void NamedLock::ReleaseLock()
{
// Got a lock?
if(mFileDescriptor == -1)
{
THROW_EXCEPTION(CommonException, NamedLockNotHeld)
}
// Close the file
if(::close(mFileDescriptor) != 0)
{
THROW_EXCEPTION(CommonException, OSFileError)
}
// Mark as unlocked
mFileDescriptor = -1;
}
|