mirror of https://gerrit.osmocom.org/libosmocore
121 lines
3.1 KiB
Smarty
121 lines
3.1 KiB
Smarty
/*
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* crcXXgen.c
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*
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* Generic CRC routines (for max XX bits poly)
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*
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* Copyright (C) 2011 Sylvain Munaut <tnt@246tNt.com>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/*! \addtogroup crcgen
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* @{
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*/
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/*! \file crcXXgen.c
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* \file Osmocom generic CRC routines (for max XX bits poly)
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*/
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#include <stdint.h>
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#include <osmocom/core/bits.h>
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#include <osmocom/core/crcXXgen.h>
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/*! \brief Compute the CRC value of a given array of hard-bits
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* \param[in] code The CRC code description to apply
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* \param[in] in Array of hard bits
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* \param[in] len Length of the array of hard bits
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* \returns The CRC value
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*/
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uintXX_t
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osmo_crcXXgen_compute_bits(const struct osmo_crcXXgen_code *code,
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const ubit_t *in, int len)
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{
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const uintXX_t poly = code->poly;
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uintXX_t crc = code->init;
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int i, n = code->bits-1;
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for (i=0; i<len; i++) {
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uintXX_t bit = in[i] & 1;
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crc ^= (bit << n);
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if (crc & (1 << n)) {
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crc <<= 1;
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crc ^= poly;
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} else {
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crc <<= 1;
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}
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crc &= (1ULL << code->bits) - 1;
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}
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crc ^= code->remainder;
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return crc;
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}
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/*! \brief Checks the CRC value of a given array of hard-bits
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* \param[in] code The CRC code description to apply
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* \param[in] in Array of hard bits
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* \param[in] len Length of the array of hard bits
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* \param[in] crc_bits Array of hard bits with the alleged CRC
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* \returns 0 if CRC matches. 1 in case of error.
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*
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* The crc_bits array must have a length of code->len
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*/
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int
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osmo_crcXXgen_check_bits(const struct osmo_crcXXgen_code *code,
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const ubit_t *in, int len, const ubit_t *crc_bits)
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{
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uintXX_t crc;
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int i;
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crc = osmo_crcXXgen_compute_bits(code, in, len);
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for (i=0; i<code->bits; i++)
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if (crc_bits[i] ^ ((crc >> (code->bits-i-1)) & 1))
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return 1;
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return 0;
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}
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/*! \brief Computes and writes the CRC value of a given array of bits
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* \param[in] code The CRC code description to apply
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* \param[in] in Array of hard bits
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* \param[in] len Length of the array of hard bits
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* \param[in] crc_bits Array of hard bits to write the computed CRC to
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*
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* The crc_bits array must have a length of code->len
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*/
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void
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osmo_crcXXgen_set_bits(const struct osmo_crcXXgen_code *code,
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const ubit_t *in, int len, ubit_t *crc_bits)
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{
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uintXX_t crc;
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int i;
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crc = osmo_crcXXgen_compute_bits(code, in, len);
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for (i=0; i<code->bits; i++)
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crc_bits[i] = ((crc >> (code->bits-i-1)) & 1);
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}
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/*! @} */
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/* vim: set syntax=c: */
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