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46
47 #include "qtlockedfile.h"
48 #include <qt_windows.h>
49 #include <QtCore/QFileInfo>
50
51 #define MUTEX_PREFIX "QtLockedFile mutex "
52 // Maximum number of concurrent read locks. Must not be greater than MAXIMUM_WAIT_OBJECTS
53 #define MAX_READERS MAXIMUM_WAIT_OBJECTS
54
getMutexHandle(int idx,bool doCreate)55 Qt::HANDLE QtLockedFile::getMutexHandle(int idx, bool doCreate)
56 {
57 if (mutexname.isEmpty()) {
58 QFileInfo fi(*this);
59 mutexname = QString::fromLatin1(MUTEX_PREFIX)
60 + fi.absoluteFilePath().toLower();
61 }
62 QString mname(mutexname);
63 if (idx >= 0)
64 mname += QString::number(idx);
65
66 Qt::HANDLE mutex;
67 if (doCreate) {
68 mutex = CreateMutexW(NULL, FALSE, (TCHAR*)mname.utf16());
69 if (!mutex) {
70 qErrnoWarning("QtLockedFile::lock(): CreateMutex failed");
71 return 0;
72 }
73 }
74 else {
75 mutex = OpenMutexW(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, (TCHAR*)mname.utf16());
76 if (!mutex) {
77 if (GetLastError() != ERROR_FILE_NOT_FOUND)
78 qErrnoWarning("QtLockedFile::lock(): OpenMutex failed");
79 return 0;
80 }
81 }
82 return mutex;
83 }
84
waitMutex(Qt::HANDLE mutex,bool doBlock)85 bool QtLockedFile::waitMutex(Qt::HANDLE mutex, bool doBlock)
86 {
87 Q_ASSERT(mutex);
88 DWORD res = WaitForSingleObject(mutex, doBlock ? INFINITE : 0);
89 switch (res) {
90 case WAIT_OBJECT_0:
91 case WAIT_ABANDONED:
92 return true;
93 break;
94 case WAIT_TIMEOUT:
95 break;
96 default:
97 qErrnoWarning("QtLockedFile::lock(): WaitForSingleObject failed");
98 }
99 return false;
100 }
101
102
103
lock(LockMode mode,bool block)104 bool QtLockedFile::lock(LockMode mode, bool block)
105 {
106 if (!isOpen()) {
107 qWarning("QtLockedFile::lock(): file is not opened");
108 return false;
109 }
110
111 if (mode == NoLock)
112 return unlock();
113
114 if (mode == m_lock_mode)
115 return true;
116
117 if (m_lock_mode != NoLock)
118 unlock();
119
120 if (!wmutex && !(wmutex = getMutexHandle(-1, true)))
121 return false;
122
123 if (!waitMutex(wmutex, block))
124 return false;
125
126 if (mode == ReadLock) {
127 int idx = 0;
128 for (; idx < MAX_READERS; idx++) {
129 rmutex = getMutexHandle(idx, false);
130 if (!rmutex || waitMutex(rmutex, false))
131 break;
132 CloseHandle(rmutex);
133 }
134 bool ok = true;
135 if (idx >= MAX_READERS) {
136 qWarning("QtLockedFile::lock(): too many readers");
137 rmutex = 0;
138 ok = false;
139 }
140 else if (!rmutex) {
141 rmutex = getMutexHandle(idx, true);
142 if (!rmutex || !waitMutex(rmutex, false))
143 ok = false;
144 }
145 if (!ok && rmutex) {
146 CloseHandle(rmutex);
147 rmutex = 0;
148 }
149 ReleaseMutex(wmutex);
150 if (!ok)
151 return false;
152 }
153 else {
154 Q_ASSERT(rmutexes.isEmpty());
155 for (int i = 0; i < MAX_READERS; i++) {
156 Qt::HANDLE mutex = getMutexHandle(i, false);
157 if (mutex)
158 rmutexes.append(mutex);
159 }
160 if (rmutexes.size()) {
161 DWORD res = WaitForMultipleObjects(rmutexes.size(), rmutexes.constData(),
162 TRUE, block ? INFINITE : 0);
163 if (res != WAIT_OBJECT_0 && res != WAIT_ABANDONED) {
164 if (res != WAIT_TIMEOUT)
165 qErrnoWarning("QtLockedFile::lock(): WaitForMultipleObjects failed");
166 m_lock_mode = WriteLock; // trick unlock() to clean up - semiyucky
167 unlock();
168 return false;
169 }
170 }
171 }
172
173 m_lock_mode = mode;
174 return true;
175 }
176
unlock()177 bool QtLockedFile::unlock()
178 {
179 if (!isOpen()) {
180 qWarning("QtLockedFile::unlock(): file is not opened");
181 return false;
182 }
183
184 if (!isLocked())
185 return true;
186
187 if (m_lock_mode == ReadLock) {
188 ReleaseMutex(rmutex);
189 CloseHandle(rmutex);
190 rmutex = 0;
191 }
192 else {
193 foreach(Qt::HANDLE mutex, rmutexes) {
194 ReleaseMutex(mutex);
195 CloseHandle(mutex);
196 }
197 rmutexes.clear();
198 ReleaseMutex(wmutex);
199 }
200
201 m_lock_mode = QtLockedFile::NoLock;
202 return true;
203 }
204
~QtLockedFile()205 QtLockedFile::~QtLockedFile()
206 {
207 if (isOpen())
208 unlock();
209 if (wmutex)
210 CloseHandle(wmutex);
211 }
212