e0bcd61f92
builtin function, sum, is much faster than for loop. The result on my machine is as follows > def main(): > from timeit import timeit > data = bytearray().zfill(1500) > print 'new=', timeit(lambda : checksum(data), number=1000) > print 'old=', timeit(lambda : checksum_old(data), number=1000) > > new= 0.00800108909607 > old= 0.266770124435 Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
95 lines
3.4 KiB
Python
95 lines
3.4 KiB
Python
# Copyright (C) 2012 Nippon Telegraph and Telephone Corporation.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import array
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import socket
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import struct
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def carry_around_add(a, b):
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c = a + b
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return (c & 0xffff) + (c >> 16)
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def checksum(data):
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if len(data) % 2:
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data += '\x00'
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data = str(data) # input can be bytearray.
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s = sum(array.array('H', data))
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s = (s & 0xffff) + (s >> 16)
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s += (s >> 16)
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return socket.ntohs(~s & 0xffff)
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# avoid circular import
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_IPV4_PSEUDO_HEADER_PACK_STR = '!IIxBH'
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_IPV6_PSEUDO_HEADER_PACK_STR = '!16s16sI3xB'
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def checksum_ip(ipvx, length, payload):
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"""
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calculate checksum of IP pseudo header
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IPv4 pseudo header
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UDP RFC768
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TCP RFC793 3.1
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0 7 8 15 16 23 24 31
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+--------+--------+--------+--------+
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| source address |
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+--------+--------+--------+--------+
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| destination address |
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+--------+--------+--------+--------+
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| zero |protocol| length |
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+--------+--------+--------+--------+
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IPv6 pseudo header
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RFC2460 8.1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+ +
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+ Source Address +
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+ +
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+ +
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+ Destination Address +
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+ +
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Upper-Layer Packet Length |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| zero | Next Header |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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"""
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if ipvx.version == 4:
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header = struct.pack(_IPV4_PSEUDO_HEADER_PACK_STR,
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ipvx.src, ipvx.dst, ipvx.proto, length)
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elif ipvx.version == 6:
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header = struct.pack(_IPV6_PSEUDO_HEADER_PACK_STR,
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ipvx.src, ipvx.dst, length, ipvx.nxt)
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else:
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raise ValueError('Unknown IP version %d' % ipvx.version)
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buf = header + payload
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return checksum(buf)
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