+
+# replace a target file with a new contents - checks for changes
+# return True if a change occurred, in which case
+# chown/chmod settings should be taken care of
+def replace_file_with_string (target, new_contents):
+ try:
+ current=file(target).read()
+ except:
+ current=""
+ # xxx if verbose, report diffs...
+ if current==new_contents:
+ return False
+ # overwrite target file
+ f=file(target,'w')
+ f.write(new_contents)
+ f.close()
+ return True
+
+# not needed yet - should that unlink the new file ?
+#def replace_file_with_file (target, new):
+# return replace_file_with_string (target, file(new).read())
+
+####################
+# utilities functions to get (cached) information from the node
+
+# get node_id from /etc/planetlab/node_id and cache it
+_node_id=None
+def node_id():
+ global _node_id
+ if _node_id is None:
+ try:
+ _node_id=int(file("/etc/planetlab/node_id").read())
+ except:
+ _node_id=""
+ return _node_id
+
+_root_context_arch=None
+def root_context_arch():
+ global _root_context_arch
+ if not _root_context_arch:
+ sp=subprocess.Popen(["uname","-i"],stdout=subprocess.PIPE)
+ (_root_context_arch,_)=sp.communicate()
+ _root_context_arch=_root_context_arch.strip()
+ return _root_context_arch
+
+
+####################
+class NMLock:
+ def __init__(self, file):
+ logger.log("tools: Lock %s initialized." % file, 2)
+ self.fd = os.open(file, os.O_RDWR|os.O_CREAT, 0600)
+ flags = fcntl.fcntl(self.fd, fcntl.F_GETFD)
+ flags |= fcntl.FD_CLOEXEC
+ fcntl.fcntl(self.fd, fcntl.F_SETFD, flags)
+ def __del__(self):
+ os.close(self.fd)
+ def acquire(self):
+ logger.log("tools: Lock acquired.", 2)
+ fcntl.lockf(self.fd, fcntl.LOCK_SH)
+ def release(self):
+ logger.log("tools: Lock released.", 2)
+ fcntl.lockf(self.fd, fcntl.LOCK_UN)