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# --------------------------------------------------------------------------------------------
# Copyright (c) Microsoft Corporation. All rights reserved.
# Licensed under the MIT License. See License.txt in the project root for license information.
# --------------------------------------------------------------------------------------------
from io import BytesIO
import os
_DEFAULT_LENGTH = 1024 * 1024
_BYTE_BUFFER = [_DEFAULT_LENGTH, os.urandom(_DEFAULT_LENGTH)]
def get_random_bytes(buffer_length):
if buffer_length > _BYTE_BUFFER[0]:
_BYTE_BUFFER[1] = os.urandom(buffer_length)
_BYTE_BUFFER[0] = buffer_length
return _BYTE_BUFFER[1][:buffer_length]
class RandomStream(BytesIO):
def __init__(self, length, initial_buffer_length=_DEFAULT_LENGTH):
self._base_data = get_random_bytes(initial_buffer_length)
self._data_length = length
self._base_buffer_length = initial_buffer_length
self._position = 0
self._remaining = length
def __len__(self):
return self._remaining
def reset(self):
self._position = 0
self._remaining = self._data_length
def read(self, size=None):
if self._remaining == 0:
return b""
if size is None:
e = self._base_buffer_length
else:
e = size
e = min(e, self._remaining)
if e > self._base_buffer_length:
self._base_data = get_random_bytes(e)
self._base_buffer_length = e
self._remaining = self._remaining - e
self._position += e
return self._base_data[:e]
def tell(self):
return self._position
def seek(self, index, whence=0):
if whence == 0:
self._position = index
elif whence == 1:
self._position = self._position + index
elif whence == 2:
self._position = self._data_length - 1 + index
def remaining(self):
return self._remaining
class WriteStream:
def __init__(self):
self._position = 0
def reset(self):
self._position = 0
def write(self, content):
length = len(content)
self._position += length
return length
def seek(self, index):
self._position = index
def seekable(self):
return True
def tell(self):
return self._position
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