Speed HMAC.copy() by installing a secret backdoor argument to
HMAC.__init__(). Adapted from SF patch 895445 "hmac.HMAC.copy() speedup"
by Trevor Perrin, who reported that this approach increased throughput
of his hmac-intensive app by 30%.
diff --git a/Lib/hmac.py b/Lib/hmac.py
index db9b404..11b0fb3 100644
--- a/Lib/hmac.py
+++ b/Lib/hmac.py
@@ -12,6 +12,11 @@
# hashing module used.
digest_size = None
+# A unique object passed by HMAC.copy() to the HMAC constructor, in order
+# that the latter return very quickly. HMAC("") in contrast is quite
+# expensive.
+_secret_backdoor_key = []
+
class HMAC:
"""RFC2104 HMAC class.
@@ -25,6 +30,10 @@
msg: Initial input for the hash, if provided.
digestmod: A module supporting PEP 247. Defaults to the md5 module.
"""
+
+ if key is _secret_backdoor_key: # cheap
+ return
+
if digestmod is None:
import md5
digestmod = md5
@@ -60,8 +69,9 @@
An update to this copy won't affect the original object.
"""
- other = HMAC("")
+ other = HMAC(_secret_backdoor_key)
other.digestmod = self.digestmod
+ other.digest_size = self.digest_size
other.inner = self.inner.copy()
other.outer = self.outer.copy()
return other