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from __future__ import absolute_import
from __future__ import division
from pwnlib.context import context
class Buffer(object):
"""
List of strings with some helper routines.
Example:
>>> b = Buffer()
>>> b.add(b"A" * 10)
>>> b.add(b"B" * 10)
>>> len(b)
20
>>> b.get(1)
b'A'
>>> len(b)
19
>>> b.get(9999)
b'AAAAAAAAABBBBBBBBBB'
>>> len(b)
0
>>> b.get(1)
b''
Implementation Details:
Implemented as a list. Strings are added onto the end.
The ``0th`` item in the buffer is the oldest item, and
will be received first.
"""
def __init__(self, buffer_fill_size = None):
self.data = [] # Buffer
self.size = 0 # Length
self.buffer_fill_size = buffer_fill_size
def __len__(self):
"""
>>> b = Buffer()
>>> b.add(b'lol')
>>> len(b) == 3
True
>>> b.add(b'foobar')
>>> len(b) == 9
True
"""
return self.size
def __nonzero__(self):
return len(self) > 0
def __contains__(self, x):
"""
>>> b = Buffer()
>>> b.add(b'asdf')
>>> b'x' in b
False
>>> b.add(b'x')
>>> b'x' in b
True
"""
for b in self.data:
if x in b:
return True
return False
def index(self, x):
"""
>>> b = Buffer()
>>> b.add(b'asdf')
>>> b.add(b'qwert')
>>> b.index(b't') == len(b) - 1
True
"""
sofar = 0
for b in self.data:
if x in b:
return sofar + b.index(x)
sofar += len(b)
raise IndexError()
def add(self, data):
"""
Adds data to the buffer.
Arguments:
data(str,Buffer): Data to add
"""
# Fast path for ''
if not data: return
if isinstance(data, Buffer):
self.size += data.size
self.data += data.data
else:
self.size += len(data)
self.data.append(data)
def unget(self, data):
"""
Places data at the front of the buffer.
Arguments:
data(str,Buffer): Data to place at the beginning of the buffer.
Example:
>>> b = Buffer()
>>> b.add(b"hello")
>>> b.add(b"world")
>>> b.get(5)
b'hello'
>>> b.unget(b"goodbye")
>>> b.get()
b'goodbyeworld'
"""
if isinstance(data, Buffer):
self.data = data.data + self.data
self.size += data.size
else:
self.data.insert(0, data)
self.size += len(data)
def get(self, want=float('inf')):
"""
Retrieves bytes from the buffer.
Arguments:
want(int): Maximum number of bytes to fetch
Returns:
Data as string
Example:
>>> b = Buffer()
>>> b.add(b'hello')
>>> b.add(b'world')
>>> b.get(1)
b'h'
>>> b.get()
b'elloworld'
"""
# Fast path, get all of the data
if want >= self.size:
data = b''.join(self.data)
self.size = 0
self.data = []
return data
# Slow path, find the correct-index chunk
have = 0
i = 0
while want >= have:
have += len(self.data[i])
i += 1
# Join the chunks, evict from the buffer
data = b''.join(self.data[:i])
self.data = self.data[i:]
# If the last chunk puts us over the limit,
# stick the extra back at the beginning.
if have > want:
extra = data[want:]
data = data[:want]
self.data.insert(0, extra)
# Size update
self.size -= len(data)
return data
def get_fill_size(self, size=None):
"""
Retrieves the default fill size for this buffer class.
Arguments:
size (int): (Optional) If set and not None, returns the size variable back.
Returns:
Fill size as integer if size is None, else size.
"""
if size is None:
size = self.buffer_fill_size
with context.local(buffer_size=size):
return context.buffer_size
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