1 files changed, 83 insertions, 0 deletions
diff --git a/WebKitTools/Scripts/webkitpy/common/system/file_lock.py b/WebKitTools/Scripts/webkitpy/common/system/file_lock.py
new file mode 100644
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--- /dev/null
+++ b/WebKitTools/Scripts/webkitpy/common/system/file_lock.py
@@ -0,0 +1,83 @@
+#!/usr/bin/env python
+# Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged
+#
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY UNIVERSITY OF SZEGED ``AS IS'' AND ANY
+# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL UNIVERSITY OF SZEGED OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+# EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+# PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+# OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""This class helps to lock files exclusively across processes."""
+
+import logging
+import os
+import sys
+import time
+
+
+_log = logging.getLogger("webkitpy.common.system.file_lock")
+
+
+class FileLock(object):
+
+    def __init__(self, lock_file_path, max_wait_time_sec=20):
+        self._lock_file_path = lock_file_path
+        self._lock_file_descriptor = None
+        self._max_wait_time_sec = max_wait_time_sec
+
+    def _create_lock(self):
+        if sys.platform in ('darwin', 'linux2', 'cygwin'):
+            import fcntl
+            fcntl.flock(self._lock_file_descriptor, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        elif sys.platform == 'win32':
+            import msvcrt
+            msvcrt.locking(self._lock_file_descriptor, msvcrt.LK_NBLCK, 32)
+
+    def _remove_lock(self):
+        if sys.platform in ('darwin', 'linux2', 'cygwin'):
+            import fcntl
+            fcntl.flock(self._lock_file_descriptor, fcntl.LOCK_UN)
+        elif sys.platform == 'win32':
+            import msvcrt
+            msvcrt.locking(self._lock_file_descriptor, msvcrt.LK_UNLCK, 32)
+
+    def acquire_lock(self):
+        self._lock_file_descriptor = os.open(self._lock_file_path, os.O_TRUNC | os.O_CREAT)
+        start_time = time.time()
+        while True:
+            try:
+                self._create_lock()
+                return True
+            except IOError:
+                if time.time() - start_time > self._max_wait_time_sec:
+                    _log.debug("File locking failed: %s" % str(sys.exc_info()))
+                    os.close(self._lock_file_descriptor)
+                    self._lock_file_descriptor = None
+                    return False
+
+    def release_lock(self):
+        try:
+            if self._lock_file_descriptor:
+                self._remove_lock()
+                os.close(self._lock_file_descriptor)
+                self._lock_file_descriptor = None
+            os.unlink(self._lock_file_path)
+        except (IOError, OSError):
+            _log.debug("Warning in release lock: %s" % str(sys.exc_info()))