Issue #13031: Small speed-up for tarfile when unzipping tarfiles.
Patch by Justin Peel.
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 9d38421..8549677 100644
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -245,8 +245,8 @@
the high bit set. So we calculate two checksums, unsigned and
signed.
"""
- unsigned_chksum = 256 + sum(struct.unpack("148B", buf[:148]) + struct.unpack("356B", buf[156:512]))
- signed_chksum = 256 + sum(struct.unpack("148b", buf[:148]) + struct.unpack("356b", buf[156:512]))
+ unsigned_chksum = 256 + sum(struct.unpack_from("148B8x356B", buf))
+ signed_chksum = 256 + sum(struct.unpack_from("148b8x356b", buf))
return unsigned_chksum, signed_chksum
def copyfileobj(src, dst, length=None):