0153f492ea
Add a helper function to calculate the checksum. Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
28 lines
860 B
Python
28 lines
860 B
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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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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s = 0
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for i in range(0, len(data), 2):
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w = data[i] + (data[i + 1] << 8)
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s = carry_around_add(s, w)
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return ~s & 0xffff
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