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46
47 #include "qtlockedfile.h"
48 #include <qt_windows.h>
49 #include <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
55 #if QT_VERSION >= 0x050000
56 #define QT_WA(unicode, ansi) unicode
57 #endif
58
getMutexHandle(int idx,bool doCreate)59 Qt::HANDLE QtLockedFile::getMutexHandle(int idx, bool doCreate)
60 {
61 if (mutexname.isEmpty()) {
62 QFileInfo fi(*this);
63 mutexname = QString::fromLatin1(MUTEX_PREFIX)
64 + fi.absoluteFilePath().toLower();
65 }
66 QString mname(mutexname);
67 if (idx >= 0)
68 mname += QString::number(idx);
69
70 Qt::HANDLE mutex;
71 if (doCreate) {
72 QT_WA( { mutex = CreateMutexW(NULL, FALSE, (WCHAR*)mname.utf16()); },
73 { mutex = CreateMutexA(NULL, FALSE, mname.toLocal8Bit().constData()); } );
74 if (!mutex) {
75 qErrnoWarning("QtLockedFile::lock(): CreateMutex failed");
76 return 0;
77 }
78 }
79 else {
80 QT_WA( { mutex = OpenMutexW(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, (WCHAR*)mname.utf16()); },
81 { mutex = OpenMutexA(SYNCHRONIZE | MUTEX_MODIFY_STATE, FALSE, mname.toLocal8Bit().constData()); } );
82 if (!mutex) {
83 if (GetLastError() != ERROR_FILE_NOT_FOUND)
84 qErrnoWarning("QtLockedFile::lock(): OpenMutex failed");
85 return 0;
86 }
87 }
88 return mutex;
89 }
90
waitMutex(Qt::HANDLE mutex,bool doBlock)91 bool QtLockedFile::waitMutex(Qt::HANDLE mutex, bool doBlock)
92 {
93 Q_ASSERT(mutex);
94 DWORD res = WaitForSingleObject(mutex, doBlock ? INFINITE : 0);
95 switch (res) {
96 case WAIT_OBJECT_0:
97 case WAIT_ABANDONED:
98 return true;
99 break;
100 case WAIT_TIMEOUT:
101 break;
102 default:
103 qErrnoWarning("QtLockedFile::lock(): WaitForSingleObject failed");
104 }
105 return false;
106 }
107
108
109
lock(LockMode mode,bool block)110 bool QtLockedFile::lock(LockMode mode, bool block)
111 {
112 if (!isOpen()) {
113 qWarning("QtLockedFile::lock(): file is not opened");
114 return false;
115 }
116
117 if (mode == NoLock)
118 return unlock();
119
120 if (mode == m_lock_mode)
121 return true;
122
123 if (m_lock_mode != NoLock)
124 unlock();
125
126 if (!wmutex && !(wmutex = getMutexHandle(-1, true)))
127 return false;
128
129 if (!waitMutex(wmutex, block))
130 return false;
131
132 if (mode == ReadLock) {
133 int idx = 0;
134 for (; idx < MAX_READERS; idx++) {
135 rmutex = getMutexHandle(idx, false);
136 if (!rmutex || waitMutex(rmutex, false))
137 break;
138 CloseHandle(rmutex);
139 }
140 bool ok = true;
141 if (idx >= MAX_READERS) {
142 qWarning("QtLockedFile::lock(): too many readers");
143 rmutex = 0;
144 ok = false;
145 }
146 else if (!rmutex) {
147 rmutex = getMutexHandle(idx, true);
148 if (!rmutex || !waitMutex(rmutex, false))
149 ok = false;
150 }
151 if (!ok && rmutex) {
152 CloseHandle(rmutex);
153 rmutex = 0;
154 }
155 ReleaseMutex(wmutex);
156 if (!ok)
157 return false;
158 }
159 else {
160 Q_ASSERT(rmutexes.isEmpty());
161 for (int i = 0; i < MAX_READERS; i++) {
162 Qt::HANDLE mutex = getMutexHandle(i, false);
163 if (mutex)
164 rmutexes.append(mutex);
165 }
166 if (rmutexes.size()) {
167 DWORD res = WaitForMultipleObjects(rmutexes.size(), rmutexes.constData(),
168 TRUE, block ? INFINITE : 0);
169 if (res != WAIT_OBJECT_0 && res != WAIT_ABANDONED) {
170 if (res != WAIT_TIMEOUT)
171 qErrnoWarning("QtLockedFile::lock(): WaitForMultipleObjects failed");
172 m_lock_mode = WriteLock; // trick unlock() to clean up - semiyucky
173 unlock();
174 return false;
175 }
176 }
177 }
178
179 m_lock_mode = mode;
180 return true;
181 }
182
unlock()183 bool QtLockedFile::unlock()
184 {
185 if (!isOpen()) {
186 qWarning("QtLockedFile::unlock(): file is not opened");
187 return false;
188 }
189
190 if (!isLocked())
191 return true;
192
193 if (m_lock_mode == ReadLock) {
194 ReleaseMutex(rmutex);
195 CloseHandle(rmutex);
196 rmutex = 0;
197 }
198 else {
199 for (Qt::HANDLE mutex: rmutexes) {
200 ReleaseMutex(mutex);
201 CloseHandle(mutex);
202 }
203 rmutexes.clear();
204 ReleaseMutex(wmutex);
205 }
206
207 m_lock_mode = QtLockedFile::NoLock;
208 return true;
209 }
210
~QtLockedFile()211 QtLockedFile::~QtLockedFile()
212 {
213 if (isOpen())
214 unlock();
215 if (wmutex)
216 CloseHandle(wmutex);
217 }
218