From: Daniel Holth <dholth@fastmail.fm>
Date: Fri, 3 Jan 2014 04:17:21 +0000 (-0500)
Subject: Issue #18585: speed zipfile import by only generating zipfile._ZipDecryptor on demand
X-Git-Tag: v3.4.0b2~40
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9dee304205d34a8565f922fdad5b0f89fcff65a5;p=python

Issue #18585: speed zipfile import by only generating zipfile._ZipDecryptor on demand
---

diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index fad52a246d..173d99080c 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -475,13 +475,15 @@ class _ZipDecrypter:
                     crc = ((crc >> 1) & 0x7FFFFFFF)
             table[i] = crc
         return table
-    crctable = _GenerateCRCTable()
+    crctable = None
 
     def _crc32(self, ch, crc):
         """Compute the CRC32 primitive on one byte."""
         return ((crc >> 8) & 0xffffff) ^ self.crctable[(crc ^ ch) & 0xff]
 
     def __init__(self, pwd):
+        if _ZipDecrypter.crctable is None:
+            _ZipDecrypter.crctable = _ZipDecrypter._GenerateCRCTable()
         self.key0 = 305419896
         self.key1 = 591751049
         self.key2 = 878082192