precompute machine + pid bytes for ObjectId generation

Author: Mike Dirolf

pymongo/objectid.py

@@ -30,13 +30,28 @@
 from errors import InvalidId
 
 
+def _machine_and_pid_bytes():
+ """Get the machine and pid portion of an ObjectId.
+ """
+ # 3 bytes machine
+ machine_hash = _md5func()
+ machine_hash.update(socket.gethostname())
+ bytes = machine_hash.digest()[0:3]
+
+ # 2 bytes pid
+ bytes += struct.pack(">H", os.getpid() % 0xFFFF)
+ return bytes
+
+
 class ObjectId(object):
  """A Mongo ObjectId.
  """
 
  _inc = 0
  _inc_lock = threading.Lock()
 
+ _machine_and_pid_bytes = _machine_and_pid_bytes()
+
  def __init__(self, id=None):
  """Initialize a new ObjectId.
 
@@ -62,13 +77,8 @@ def __generate(self):
  # 4 bytes current time
  oid += struct.pack(">i", int(time.time()))
 
- # 3 bytes machine
- machine_hash = _md5func()
- machine_hash.update(socket.gethostname())
- oid += machine_hash.digest()[0:3]
-
- # 2 bytes pid
- oid += struct.pack(">H", os.getpid() % 0xFFFF)
+ # 3 bytes machine + 2 bytes pid
+ oid += ObjectId._machine_and_pid_bytes
 
  # 3 bytes inc
  ObjectId._inc_lock.acquire()