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|
##############################################################################
#
# Copyright (c) 2001-2004 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Buffers
"""
from io import BytesIO
# copy_bytes controls the size of temp. strings for shuffling data around.
COPY_BYTES = 1 << 18 # 256K
# The maximum number of bytes to buffer in a simple string.
STRBUF_LIMIT = 8192
class FileBasedBuffer:
remain = 0
def __init__(self, file, from_buffer=None):
self.file = file
if from_buffer is not None:
from_file = from_buffer.getfile()
read_pos = from_file.tell()
from_file.seek(0)
while True:
data = from_file.read(COPY_BYTES)
if not data:
break
file.write(data)
self.remain = int(file.tell() - read_pos)
from_file.seek(read_pos)
file.seek(read_pos)
def __len__(self):
return self.remain
def __nonzero__(self):
return True
__bool__ = __nonzero__ # py3
def append(self, s):
file = self.file
read_pos = file.tell()
file.seek(0, 2)
file.write(s)
file.seek(read_pos)
self.remain = self.remain + len(s)
def get(self, numbytes=-1, skip=False):
file = self.file
if not skip:
read_pos = file.tell()
if numbytes < 0:
# Read all
res = file.read()
else:
res = file.read(numbytes)
if skip:
self.remain -= len(res)
else:
file.seek(read_pos)
return res
def skip(self, numbytes, allow_prune=0):
if self.remain < numbytes:
raise ValueError(
"Can't skip %d bytes in buffer of %d bytes" % (numbytes, self.remain)
)
self.file.seek(numbytes, 1)
self.remain = self.remain - numbytes
def newfile(self):
raise NotImplementedError()
def prune(self):
file = self.file
if self.remain == 0:
read_pos = file.tell()
file.seek(0, 2)
sz = file.tell()
file.seek(read_pos)
if sz == 0:
# Nothing to prune.
return
nf = self.newfile()
while True:
data = file.read(COPY_BYTES)
if not data:
break
nf.write(data)
self.file = nf
def getfile(self):
return self.file
def close(self):
if hasattr(self.file, "close"):
self.file.close()
self.remain = 0
class TempfileBasedBuffer(FileBasedBuffer):
def __init__(self, from_buffer=None):
FileBasedBuffer.__init__(self, self.newfile(), from_buffer)
def newfile(self):
from tempfile import TemporaryFile
return TemporaryFile("w+b")
class BytesIOBasedBuffer(FileBasedBuffer):
def __init__(self, from_buffer=None):
if from_buffer is not None:
FileBasedBuffer.__init__(self, BytesIO(), from_buffer)
else:
# Shortcut. :-)
self.file = BytesIO()
def newfile(self):
return BytesIO()
def _is_seekable(fp):
if hasattr(fp, "seekable"):
return fp.seekable()
return hasattr(fp, "seek") and hasattr(fp, "tell")
class ReadOnlyFileBasedBuffer(FileBasedBuffer):
# used as wsgi.file_wrapper
def __init__(self, file, block_size=32768):
self.file = file
self.block_size = block_size # for __iter__
def prepare(self, size=None):
if _is_seekable(self.file):
start_pos = self.file.tell()
self.file.seek(0, 2)
end_pos = self.file.tell()
self.file.seek(start_pos)
fsize = end_pos - start_pos
if size is None:
self.remain = fsize
else:
self.remain = min(fsize, size)
return self.remain
def get(self, numbytes=-1, skip=False):
# never read more than self.remain (it can be user-specified)
if numbytes == -1 or numbytes > self.remain:
numbytes = self.remain
file = self.file
if not skip:
read_pos = file.tell()
res = file.read(numbytes)
if skip:
self.remain -= len(res)
else:
file.seek(read_pos)
return res
def __iter__(self): # called by task if self.filelike has no seek/tell
return self
def next(self):
val = self.file.read(self.block_size)
if not val:
raise StopIteration
return val
__next__ = next # py3
def append(self, s):
raise NotImplementedError
class OverflowableBuffer:
"""
This buffer implementation has four stages:
- No data
- Bytes-based buffer
- BytesIO-based buffer
- Temporary file storage
The first two stages are fastest for simple transfers.
"""
overflowed = False
buf = None
strbuf = b"" # Bytes-based buffer.
def __init__(self, overflow):
# overflow is the maximum to be stored in a StringIO buffer.
self.overflow = overflow
def __len__(self):
buf = self.buf
if buf is not None:
# use buf.__len__ rather than len(buf) FBO of not getting
# OverflowError on Python 2
return buf.__len__()
else:
return self.strbuf.__len__()
def __nonzero__(self):
# use self.__len__ rather than len(self) FBO of not getting
# OverflowError on Python 2
return self.__len__() > 0
__bool__ = __nonzero__ # py3
def _create_buffer(self):
strbuf = self.strbuf
if len(strbuf) >= self.overflow:
self._set_large_buffer()
else:
self._set_small_buffer()
buf = self.buf
if strbuf:
buf.append(self.strbuf)
self.strbuf = b""
return buf
def _set_small_buffer(self):
self.buf = BytesIOBasedBuffer(self.buf)
self.overflowed = False
def _set_large_buffer(self):
self.buf = TempfileBasedBuffer(self.buf)
self.overflowed = True
def append(self, s):
buf = self.buf
if buf is None:
strbuf = self.strbuf
if len(strbuf) + len(s) < STRBUF_LIMIT:
self.strbuf = strbuf + s
return
buf = self._create_buffer()
buf.append(s)
# use buf.__len__ rather than len(buf) FBO of not getting
# OverflowError on Python 2
sz = buf.__len__()
if not self.overflowed:
if sz >= self.overflow:
self._set_large_buffer()
def get(self, numbytes=-1, skip=False):
buf = self.buf
if buf is None:
strbuf = self.strbuf
if not skip:
return strbuf
buf = self._create_buffer()
return buf.get(numbytes, skip)
def skip(self, numbytes, allow_prune=False):
buf = self.buf
if buf is None:
if allow_prune and numbytes == len(self.strbuf):
# We could slice instead of converting to
# a buffer, but that would eat up memory in
# large transfers.
self.strbuf = b""
return
buf = self._create_buffer()
buf.skip(numbytes, allow_prune)
def prune(self):
"""
A potentially expensive operation that removes all data
already retrieved from the buffer.
"""
buf = self.buf
if buf is None:
self.strbuf = b""
return
buf.prune()
if self.overflowed:
# use buf.__len__ rather than len(buf) FBO of not getting
# OverflowError on Python 2
sz = buf.__len__()
if sz < self.overflow:
# Revert to a faster buffer.
self._set_small_buffer()
def getfile(self):
buf = self.buf
if buf is None:
buf = self._create_buffer()
return buf.getfile()
def close(self):
buf = self.buf
if buf is not None:
buf.close()
|
