Ben Pfaff
69 lines
2.4 KiB
C
69 lines
2.4 KiB
C
/* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
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* Junior University
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*
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* We are making the OpenFlow specification and associated documentation
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* (Software) available for public use and benefit with the expectation
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* that others will use, modify and enhance the Software and contribute
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* those enhancements back to the community. However, since we would
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* like to make the Software available for broadest use, with as few
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* restrictions as possible permission is hereby granted, free of
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* charge, to any person obtaining a copy of this Software to deal in
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* the Software under the copyrights without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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* The name and trademarks of copyright holder(s) may NOT be used in
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* advertising or publicity pertaining to the Software or any
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* derivatives without specific, written prior permission.
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*/
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#include <config.h>
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#include "crc32.h"
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void
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crc32_init(struct crc32 *crc, unsigned int polynomial)
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{
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int i;
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for (i = 0; i < CRC32_TABLE_SIZE; ++i) {
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unsigned int reg = i << 24;
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int j;
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for (j = 0; j < CRC32_TABLE_BITS; j++) {
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int topBit = (reg & 0x80000000) != 0;
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reg <<= 1;
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if (topBit)
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reg ^= polynomial;
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}
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crc->table[i] = reg;
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}
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}
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unsigned int
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crc32_calculate(const struct crc32 *crc, const void *data_, size_t n_bytes)
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{
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const uint8_t *data = data_;
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unsigned int result = 0;
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size_t i;
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for (i = 0; i < n_bytes; i++) {
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unsigned int top = result >> 24;
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top ^= data[i];
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result = (result << 8) ^ crc->table[top];
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}
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return result;
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}
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