Issue #27194: superfluous truncate calls in tarfile.py slow down extraction

Patch by Jason Fried.

Lib/tarfile.py

@@ -2150,10 +2150,10 @@ class TarFile(object):
                 for offset, size in tarinfo.sparse:
                     target.seek(offset)
                     copyfileobj(source, target, size, ReadError)
+                target.seek(tarinfo.size)
+                target.truncate()
             else:
                 copyfileobj(source, target, tarinfo.size, ReadError)
-            target.seek(tarinfo.size)
-            target.truncate()
 
     def makeunknown(self, tarinfo, targetpath):
         """Make a file from a TarInfo object with an unknown type

Misc/ACKS

@@ -458,6 +458,7 @@ Stefan Franke
 Martin Franklin
 Kent Frazier
 Bruce Frederiksen
+Jason Fried
 Robin Friedrich
 Bradley Froehle
 Ivan Frohne