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# vim: set filencoding=utf8
"""
Utilities for Manipulating Byte Streams
@author: Mike Crute (mcrute@gmail.com)
@organization: SoftGroup Interactive, Inc.
@date: May 05, 2010
"""
import struct
INT_FORMAT = struct.Struct('>I')
def pack_string(string):
"""
Pack a string into a network style byte array.
"""
return pack_int(len(string)) + string
def pack_int(integer):
"""
Pack an integer into a byte array.
"""
return INT_FORMAT.pack(integer)
def pack_mp_int(mp_int):
"""
Pack a multiple-percision integer into a byte array.
"""
return pack_string(int_to_bytes(mp_int))
def unpack_string(buf):
"""
Unpack a string from a byte array buffer returning
the string and the remainder of the buffer.
"""
length, = INT_FORMAT.unpack(buf[:4])
string = buf[4:4+length]
remainder = buf[4+length:]
return string, remainder
def unpack_mp_int(buf):
"""
Unpack a multiple-percision integer from a byte array
buffer returning the string and the remainder of the
buffer.
"""
length, = INT_FORMAT.unpack(buf[:4])
remainder = buf[4+length:]
return bytes_to_int(buf[4:4+length]), remainder
def unpack_int(buf):
"""
Unpack an integer from a byte array buffer returning the
string and the remainder of the buffer.
"""
integer, = INT_FORMAT.unpack(buf[:4])
remainder = buf[4:]
return integer, remainder
def get_packed_mp_ints(buf, count=1):
"""
Get a number of multiple-percision integers from a byte
array buffer but leaves them as network style mpints.
"""
ints = []
for _ in range(count):
length, = INT_FORMAT.unpack(buf[:4])
ints.append(buf[:4+length])
buf = buf[4+length:]
return ints
def int_to_bytes(integer):
"""
Convert an integer or a long integer to an array of
bytes.
"""
bytes = []
while integer > 0:
integer, chunk = divmod(integer, 256)
bytes.insert(0, chr(chunk))
return ''.join(bytes)
def bytes_to_int(buf):
"""
Convert an array of bytes into an integer or long
integer.
"""
integer = 0
for byte in buf:
integer <<= 8
integer += ord(byte)
return integer
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