Extension docs server: APIDataSource

chrome/common/extensions/docs/server2/fetcher_cache.py

+# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import time
+
+class FetcherCache(object):
+  """A cache for fetcher objects.
+  """
+  class Builder(object):
+    """A class to build a fetcher cache.
+    """
+    def __init__(self, fetcher, timeout_seconds):
+      self._fetcher = fetcher
+      self._timeout_seconds = timeout_seconds
+
+    def build(self, populate_function):
+      return FetcherCache(self._fetcher,
+                          self._timeout_seconds,
+                          populate_function)
+
+  class _CacheEntry(object):
+    def __init__(self, cache_data, expiry):
+      self._cache_data = cache_data
+      self._expiry = expiry
+
+    def HasExpired(self):
+      return time.time() > self._expiry
+
+  def __init__(self, fetcher, timeout_seconds, populate_function):
+    self._fetcher = fetcher
+    self._timeout_seconds = timeout_seconds
+    self._populate_function = populate_function
+    self._cache = {}
+
+  def get(self, key):
+    if key in self._cache:
+      if self._cache[key].HasExpired():
+        self._cache.pop(key)
+      else:
+        return self._cache[key]._cache_data
+    cache_data = self._fetcher.FetchResource(key).content
+    self._cache[key] = self._CacheEntry(self._populate_function(cache_data),
+                                        time.time() + self._timeout_seconds)
+    return self._cache[key]._cache_data