Author: Alex Gaynor <[email protected]>
Branch:
Changeset: r64692:7587887ac0e2
Date: 2013-05-31 13:19 -0700
http://bitbucket.org/pypy/pypy/changeset/7587887ac0e2/
Log: Optimize truncating an rStringIO (used in io.BytesIO) to empty.
diff --git a/rpython/rlib/rStringIO.py b/rpython/rlib/rStringIO.py
--- a/rpython/rlib/rStringIO.py
+++ b/rpython/rlib/rStringIO.py
@@ -101,7 +101,11 @@
self.__pos = endp
def seek(self, position, mode=0):
- if mode == 1:
+ if mode == 0:
+ if position == self.getsize():
+ self.__pos = AT_END
+ return
+ elif mode == 1:
if self.__pos == AT_END:
self.__pos = self.getsize()
position += self.__pos
@@ -168,15 +172,19 @@
Python 2.7's cStringIO module: it will not enlarge the file,
and it will always seek to the (new) end of the file."""
assert size >= 0
- if self.__bigbuffer is None or size > len(self.__bigbuffer):
- self.__copy_into_bigbuffer()
+ if size == 0:
+ self.__bigbuffer = None
+ self.__strings = None
else:
- # we can drop all extra strings
- if self.__strings is not None:
- self.__strings = None
- if size < len(self.__bigbuffer):
- del self.__bigbuffer[size:]
- if len(self.__bigbuffer) == 0:
- self.__bigbuffer = None
+ if self.__bigbuffer is None or size > len(self.__bigbuffer):
+ self.__copy_into_bigbuffer()
+ else:
+ # we can drop all extra strings
+ if self.__strings is not None:
+ self.__strings = None
+ if size < len(self.__bigbuffer):
+ del self.__bigbuffer[size:]
+ if len(self.__bigbuffer) == 0:
+ self.__bigbuffer = None
# it always has the effect of seeking at the new end
self.__pos = AT_END
diff --git a/rpython/rlib/test/test_rStringIO.py
b/rpython/rlib/test/test_rStringIO.py
--- a/rpython/rlib/test/test_rStringIO.py
+++ b/rpython/rlib/test/test_rStringIO.py
@@ -117,6 +117,13 @@
assert f.getvalue() == '\x00' * 3
assert f.tell() == 3
+def test_truncate_end():
+ f = RStringIO()
+ f.write("abc")
+ f.seek(0)
+ f.truncate(0)
+ assert f.getvalue() == ""
+
def test_bug():
f = RStringIO()
f.write('0')
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