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Checksum for image data message elements.

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FossilOrigin-Name: bfe6cf9ca48592aa3fc6f572620b48ed29ba6f383e3ef52bd913758cc9675f35
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7u83@mail.ru 2014-08-24 18:50:33 +00:00
parent c8ae7d7a46
commit 97696c7b36
1 changed files with 40 additions and 0 deletions
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src/capwap/lw_checksum.c Normal file
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/*
This file is part of libcapwap.
libcapwap is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
libcapwap is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Foobar. If not, see <http://www.gnu.org/licenses/>.
*/
#include "lwapp.h"
/**
* Calculate the 16-bit checksum for LWAPP image data message
* elements with opcode 3 - used by Cisco also in CAPWAP
*/
uint16_t lw_checksum(uint8_t * d, int len)
{
int i;
uint32_t cs = 0;
for (i = 0; i < len; i += 2) {
uint16_t w = d[i] << 8;
if (i + 1 < len)
w |= d[i + 1];
cs += w ^= 0xffff;
cs += cs >> 16;
cs &= 0xffff;
}
return (uint16_t) cs;
}