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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
from tempfile import TemporaryFile
# 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(object):
seekable = True
remaining = 0 # -1 would indicate an infinite stream
def __bool__(self):
return self.remaining != 0
__nonzero = __bool__ # py2
def append(self, s):
assert self.seekable
file = self.file
read_pos = file.tell()
file.seek(0, 2)
file.write(s)
file.seek(read_pos)
self.remaining += len(s)
def read(self, numbytes=-1):
file = self.file
remaining = self.remaining
if remaining != -1 and numbytes > remaining:
numbytes = remaining
if numbytes < 0:
# Read all
res = file.read()
else:
res = file.read(numbytes)
numres = len(res)
if remaining == -1:
# keep remaining at -1 until EOF
if not numres and numbytes != 0:
self.remaining = 0
else:
self.remaining -= numres
return res
def rollback(self, numbytes):
assert self.seekable
self.file.seek(-numbytes, 1)
self.remaining += numbytes
def close(self):
self.remaining = 0
if hasattr(self.file, 'close'):
self.file.close()
class TempfileBasedBuffer(FileBasedBuffer):
def __init__(self, from_buffer=None):
file = TemporaryFile('w+b')
if from_buffer is not None:
while True:
data = from_buffer.read(COPY_BYTES)
if not data:
break
file.write(data)
self.remaining += len(data)
file.seek(0)
self.file = file
class BytesIOBasedBuffer(FileBasedBuffer):
def __init__(self, value=None):
self.file = BytesIO(value)
if value is not None:
self.remaining = len(value)
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
remaining = -1
def __init__(self, file, block_size=32768):
self.file = file
self.block_size = block_size # for __iter__
self.seekable = _is_seekable(file)
def prepare(self, size=None):
if self.seekable:
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.remaining = fsize
else:
self.remaining = min(fsize, size)
return self.remaining
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__ # py2
def append(self, s):
raise NotImplementedError
class OverflowableBuffer(object):
"""
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.
"""
seekable = True
remaining = 0
overflowed = False
buf = None
strbuf = b'' # Bytes-based buffer.
def __init__(self, overflow):
# overflow is the maximum to be stored in a BytesIO buffer.
self.overflow = overflow
def __bool__(self):
return self.remaining != 0
__nonzero = __bool__ # py2
def append(self, s):
buf = self.buf
if buf is None:
strbuf = self.strbuf if self.remaining else b''
if len(strbuf) + len(s) < STRBUF_LIMIT:
self.strbuf = strbuf + s
self.remaining += len(s)
return
else:
buf = BytesIOBasedBuffer(self.strbuf + s)
self.buf = buf
self.strbuf = b''
else:
buf.append(s)
remaining = buf.remaining
self.remaining = remaining
if not self.overflowed and remaining > self.overflow:
self.buf = TempfileBasedBuffer(buf)
self.overflowed = True
def read(self, numbytes=-1):
buf = self.buf
if buf is None:
if self.remaining <= numbytes or numbytes == -1:
self.remaining = 0
return self.strbuf
buf = self.buf = BytesIOBasedBuffer(self.strbuf)
data = buf.read(numbytes)
self.remaining = buf.remaining
return data
def rollback(self, numbytes):
buf = self.buf
if buf is None:
self.strbuf = self.strbuf[-numbytes:]
self.remaining = len(self.strbuf)
return
buf.rollback(numbytes)
self.remaining = buf.remaining
def close(self):
self.remaining = 0
self.strbuf = b''
buf = self.buf
if buf is not None:
buf.close()
def getfile(self):
buf = self.buf
if buf is None:
buf = self.buf = BytesIOBasedBuffer(self.strbuf)
return buf.file
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