[Python-checkins] cpython: Use a flag to indicate when the circular queue is fully populated and stable.

Tue May 1 05:49:05 CEST 2012

http://hg.python.org/cpython/rev/f5bb290c751a
changeset: 76680:f5bb290c751a
parent: 76678:ab63e874265e
user: Raymond Hettinger <python at rcn.com>
date: Mon Apr 30 20:48:55 2012 -0700
summary:
 Use a flag to indicate when the circular queue is fully populated and stable.
files:
 Lib/functools.py | 21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/Lib/functools.py b/Lib/functools.py
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -176,6 +176,7 @@
 
 cache = {}
 hits = misses = currsize = 0
+ full = False
 cache_get = cache.get # bound method to lookup a key or return None
 lock = Lock() # because linkedlist updates aren't threadsafe
 root = [] # root of the circular doubly linked list
@@ -224,7 +225,7 @@
 
 def wrapper(*args, **kwds):
 # size limited caching that tracks accesses by recency
- nonlocal root, hits, misses, currsize
+ nonlocal root, hits, misses, currsize, full
 key = make_key(args, kwds, typed) if kwds or typed else args
 with lock:
 link = cache_get(key)
@@ -247,13 +248,7 @@
 # update is already done, we need only return the
 # computed result and update the count of misses.
 pass
- if currsize < maxsize:
- # put result in a new link at the front of the queue
- last = root[PREV]
- link = [last, root, key, result]
- cache[key] = last[NEXT] = root[PREV] = link
- currsize += 1
- else:
+ elif full:
 # use root to store the new key and result
 root[KEY] = key
 root[RESULT] = result
@@ -262,6 +257,13 @@
 root = root[NEXT]
 del cache[root[KEY]]
 root[KEY] = root[RESULT] = None
+ else:
+ # put result in a new link at the front of the queue
+ last = root[PREV]
+ link = [last, root, key, result]
+ cache[key] = last[NEXT] = root[PREV] = link
+ currsize += 1
+ full = (currsize == maxsize)
 misses += 1
 return result
 
@@ -272,11 +274,12 @@
 
 def cache_clear():
 """Clear the cache and cache statistics"""
- nonlocal hits, misses, currsize
+ nonlocal hits, misses, currsize, full
 with lock:
 cache.clear()
 root[:] = [root, root, None, None]
 hits = misses = currsize = 0
+ full = False
 
 wrapper.cache_info = cache_info
 wrapper.cache_clear = cache_clear
-- 
Repository URL: http://hg.python.org/cpython
