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Issue #3476: make BufferedReader and BufferedWriter thread-safe

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This commit is contained in:
Antoine Pitrou 2008-08-14 21:04:30 +00:00
parent 63d325e8c4
commit 11ec65d82b
3 changed files with 144 additions and 40 deletions
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102
Lib/io.py
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@ -63,6 +63,7 @@ import sys
import codecs
import _fileio
import warnings
import threading
# open() uses st_blksize whenever we can
DEFAULT_BUFFER_SIZE = 8 * 1024 # bytes
@ -908,6 +909,7 @@ class BufferedReader(_BufferedIOMixin):
_BufferedIOMixin.__init__(self, raw)
self.buffer_size = buffer_size
self._reset_read_buf()
self._read_lock = threading.Lock()
def _reset_read_buf(self):
self._read_buf = b""
@ -921,6 +923,10 @@ class BufferedReader(_BufferedIOMixin):
mode. If n is negative, read until EOF or until read() would
block.
"""
with self._read_lock:
return self._read_unlocked(n)
def _read_unlocked(self, n=None):
nodata_val = b""
empty_values = (b"", None)
buf = self._read_buf
@ -973,6 +979,10 @@ class BufferedReader(_BufferedIOMixin):
do at most one raw read to satisfy it. We never return more
than self.buffer_size.
"""
with self._read_lock:
return self._peek_unlocked(n)
def _peek_unlocked(self, n=0):
want = min(n, self.buffer_size)
have = len(self._read_buf) - self._read_pos
if have < want:
@ -989,18 +999,21 @@ class BufferedReader(_BufferedIOMixin):
# only return buffered bytes. Otherwise, we do one raw read.
if n <= 0:
return b""
self.peek(1)
return self.read(min(n, len(self._read_buf) - self._read_pos))
with self._read_lock:
self._peek_unlocked(1)
return self._read_unlocked(
min(n, len(self._read_buf) - self._read_pos))
def tell(self):
return self.raw.tell() - len(self._read_buf) + self._read_pos
def seek(self, pos, whence=0):
if whence == 1:
pos -= len(self._read_buf) - self._read_pos
pos = self.raw.seek(pos, whence)
self._reset_read_buf()
return pos
with self._read_lock:
if whence == 1:
pos -= len(self._read_buf) - self._read_pos
pos = self.raw.seek(pos, whence)
self._reset_read_buf()
return pos
class BufferedWriter(_BufferedIOMixin):
@ -1022,43 +1035,51 @@ class BufferedWriter(_BufferedIOMixin):
if max_buffer_size is None
else max_buffer_size)
self._write_buf = bytearray()
self._write_lock = threading.Lock()
def write(self, b):
if self.closed:
raise ValueError("write to closed file")
if isinstance(b, unicode):
raise TypeError("can't write unicode to binary stream")
# XXX we can implement some more tricks to try and avoid partial writes
if len(self._write_buf) > self.buffer_size:
# We're full, so let's pre-flush the buffer
try:
self.flush()
except BlockingIOError as e:
# We can't accept anything else.
# XXX Why not just let the exception pass through?
raise BlockingIOError(e.errno, e.strerror, 0)
before = len(self._write_buf)
self._write_buf.extend(b)
written = len(self._write_buf) - before
if len(self._write_buf) > self.buffer_size:
try:
self.flush()
except BlockingIOError as e:
if (len(self._write_buf) > self.max_buffer_size):
# We've hit max_buffer_size. We have to accept a partial
# write and cut back our buffer.
overage = len(self._write_buf) - self.max_buffer_size
self._write_buf = self._write_buf[:self.max_buffer_size]
raise BlockingIOError(e.errno, e.strerror, overage)
return written
with self._write_lock:
# XXX we can implement some more tricks to try and avoid
# partial writes
if len(self._write_buf) > self.buffer_size:
# We're full, so let's pre-flush the buffer
try:
self._flush_unlocked()
except BlockingIOError as e:
# We can't accept anything else.
# XXX Why not just let the exception pass through?
raise BlockingIOError(e.errno, e.strerror, 0)
before = len(self._write_buf)
self._write_buf.extend(b)
written = len(self._write_buf) - before
if len(self._write_buf) > self.buffer_size:
try:
self._flush_unlocked()
except BlockingIOError as e:
if len(self._write_buf) > self.max_buffer_size:
# We've hit max_buffer_size. We have to accept a
# partial write and cut back our buffer.
overage = len(self._write_buf) - self.max_buffer_size
self._write_buf = self._write_buf[:self.max_buffer_size]
raise BlockingIOError(e.errno, e.strerror, overage)
return written
def truncate(self, pos=None):
self.flush()
if pos is None:
pos = self.raw.tell()
return self.raw.truncate(pos)
with self._write_lock:
self._flush_unlocked()
if pos is None:
pos = self.raw.tell()
return self.raw.truncate(pos)
def flush(self):
with self._write_lock:
self._flush_unlocked()
def _flush_unlocked(self):
if self.closed:
raise ValueError("flush of closed file")
written = 0
@ -1077,8 +1098,9 @@ class BufferedWriter(_BufferedIOMixin):
return self.raw.tell() + len(self._write_buf)
def seek(self, pos, whence=0):
self.flush()
return self.raw.seek(pos, whence)
with self._write_lock:
self._flush_unlocked()
return self.raw.seek(pos, whence)
class BufferedRWPair(BufferedIOBase):
@ -1168,7 +1190,8 @@ class BufferedRandom(BufferedWriter, BufferedReader):
# First do the raw seek, then empty the read buffer, so that
# if the raw seek fails, we don't lose buffered data forever.
pos = self.raw.seek(pos, whence)
self._reset_read_buf()
with self._read_lock:
self._reset_read_buf()
return pos
def tell(self):
@ -1205,8 +1228,9 @@ class BufferedRandom(BufferedWriter, BufferedReader):
def write(self, b):
if self._read_buf:
# Undo readahead
self.raw.seek(self._read_pos - len(self._read_buf), 1)
self._reset_read_buf()
with self._read_lock:
self.raw.seek(self._read_pos - len(self._read_buf), 1)
self._reset_read_buf()
return BufferedWriter.write(self, b)