add hg and python

1 files changed, 137 insertions, 0 deletions

diff --git a/sys/src/cmd/hg/mercurial/lock.py b/sys/src/cmd/hg/mercurial/lock.py
new file mode 100644
index 000000000..a3d116e6a
--- /dev/null
+++ b/sys/src/cmd/hg/mercurial/lock.py
@@ -0,0 +1,137 @@
+# lock.py - simple advisory locking scheme for mercurial
+#
+# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2, incorporated herein by reference.
+
+import util, error
+import errno, os, socket, time
+import warnings
+
+class lock(object):
+    '''An advisory lock held by one process to control access to a set
+    of files.  Non-cooperating processes or incorrectly written scripts
+    can ignore Mercurial's locking scheme and stomp all over the
+    repository, so don't do that.
+
+    Typically used via localrepository.lock() to lock the repository
+    store (.hg/store/) or localrepository.wlock() to lock everything
+    else under .hg/.'''
+
+    # lock is symlink on platforms that support it, file on others.
+
+    # symlink is used because create of directory entry and contents
+    # are atomic even over nfs.
+
+    # old-style lock: symlink to pid
+    # new-style lock: symlink to hostname:pid
+
+    _host = None
+
+    def __init__(self, file, timeout=-1, releasefn=None, desc=None):
+        self.f = file
+        self.held = 0
+        self.timeout = timeout
+        self.releasefn = releasefn
+        self.desc = desc
+        self.lock()
+
+    def __del__(self):
+        if self.held:
+            warnings.warn("use lock.release instead of del lock",
+                    category=DeprecationWarning,
+                    stacklevel=2)
+
+            # ensure the lock will be removed
+            # even if recursive locking did occur
+            self.held = 1
+
+        self.release()
+
+    def lock(self):
+        timeout = self.timeout
+        while 1:
+            try:
+                self.trylock()
+                return 1
+            except error.LockHeld, inst:
+                if timeout != 0:
+                    time.sleep(1)
+                    if timeout > 0:
+                        timeout -= 1
+                    continue
+                raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc,
+                                     inst.locker)
+
+    def trylock(self):
+        if self.held:
+            self.held += 1
+            return
+        if lock._host is None:
+            lock._host = socket.gethostname()
+        lockname = '%s:%s' % (lock._host, os.getpid())
+        while not self.held:
+            try:
+                util.makelock(lockname, self.f)
+                self.held = 1
+            except (OSError, IOError), why:
+                if why.errno == errno.EEXIST:
+                    locker = self.testlock()
+                    if locker is not None:
+                        raise error.LockHeld(errno.EAGAIN, self.f, self.desc,
+                                             locker)
+                else:
+                    raise error.LockUnavailable(why.errno, why.strerror,
+                                                why.filename, self.desc)
+
+    def testlock(self):
+        """return id of locker if lock is valid, else None.
+
+        If old-style lock, we cannot tell what machine locker is on.
+        with new-style lock, if locker is on this machine, we can
+        see if locker is alive.  If locker is on this machine but
+        not alive, we can safely break lock.
+
+        The lock file is only deleted when None is returned.
+
+        """
+        locker = util.readlock(self.f)
+        try:
+            host, pid = locker.split(":", 1)
+        except ValueError:
+            return locker
+        if host != lock._host:
+            return locker
+        try:
+            pid = int(pid)
+        except:
+            return locker
+        if util.testpid(pid):
+            return locker
+        # if locker dead, break lock.  must do this with another lock
+        # held, or can race and break valid lock.
+        try:
+            l = lock(self.f + '.break')
+            l.trylock()
+            os.unlink(self.f)
+            l.release()
+        except error.LockError:
+            return locker
+
+    def release(self):
+        if self.held > 1:
+            self.held -= 1
+        elif self.held is 1:
+            self.held = 0
+            if self.releasefn:
+                self.releasefn()
+            try:
+                os.unlink(self.f)
+            except: pass
+
+def release(*locks):
+    for lock in locks:
+        if lock is not None:
+            lock.release()
+