Speed up next() by disabling snapshot updating then.
diff --git a/Lib/io.py b/Lib/io.py
index f9e846b..21f72c8 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -1,7 +1,7 @@
"""New I/O library conforming to PEP 3116.
-This is an early prototype; eventually some of this will be
-reimplemented in C and the rest may be turned into a package.
+This is a prototype; hopefully eventually some of this will be
+reimplemented in C.
Conformance of alternative implementations: all arguments are intended
to be positional-only except the arguments of the open() function.
@@ -11,6 +11,7 @@
names like __iter__). Only the top-level names listed in the __all__
variable are part of the specification.
+XXX edge cases when switching between reading/writing
XXX need to default buffer size to 1 if isatty()
XXX need to support 1 meaning line-buffered
XXX don't use assert to validate input requirements
@@ -877,7 +878,7 @@
Character and line based layer over a BufferedIOBase object.
"""
- _CHUNK_SIZE = 64
+ _CHUNK_SIZE = 128
def __init__(self, buffer, encoding=None, newline=None):
if newline not in (None, "\n", "\r\n"):
@@ -894,7 +895,7 @@
self._decoder_in_rest_pickle = None
self._pending = ""
self._snapshot = None
- self._seekable = self.buffer.seekable()
+ self._seekable = self._telling = self.buffer.seekable()
# A word about _snapshot. This attribute is either None, or a
# tuple (decoder_pickle, readahead, pending) where decoder_pickle
@@ -908,6 +909,7 @@
def flush(self):
self.buffer.flush()
+ self._telling = self._seekable
def close(self):
self.flush()
@@ -945,7 +947,7 @@
def _read_chunk(self):
assert self._decoder is not None
- if not self._seekable:
+ if not self._telling:
readahead = self.buffer.read(self._CHUNK_SIZE)
pending = self._decoder.decode(readahead, not readahead)
return readahead, pending
@@ -976,6 +978,8 @@
def tell(self):
if not self._seekable:
raise IOError("Underlying stream is not seekable")
+ if not self._telling:
+ raise IOError("Telling position disabled by next() call")
self.flush()
position = self.buffer.tell()
if self._decoder is None or self._snapshot is None:
@@ -1016,6 +1020,7 @@
(whence,))
if pos < 0:
raise ValueError("Negative seek position %r" % (pos,))
+ self.flush()
orig_pos = pos
ds, pos = self._decode_decoder_state(pos)
if not ds:
@@ -1050,6 +1055,15 @@
self._pending = res[n:]
return res[:n]
+ def next(self) -> str:
+ self._telling = False
+ line = self.readline()
+ if not line:
+ self._snapshot = None
+ self._telling = self._seekable
+ raise StopIteration
+ return line
+
def readline(self, limit=None):
if limit is not None:
# XXX Hack to support limit argument, for backwards compatibility