/*! \file crcXXgen.c * Osmocom generic CRC routines (for max XX bits poly). */ /* * Copyright (C) 2011 Sylvain Munaut <tnt@246tNt.com> * * All Rights Reserved * * SPDX-License-Identifier: GPL-2.0+ * * This program 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 2 of the License, or * (at your option) any later version. * * This program 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 this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ /*! \addtogroup crc * @{ * Osmocom generic CRC routines (for max XX bits poly). * * \file crcXXgen.c.tpl */ #include <stdint.h> #include <osmocom/core/bits.h> #include <osmocom/core/crcXXgen.h> /*! Compute the CRC value of a given array of hard-bits * \param[in] code The CRC code description to apply * \param[in] in Array of hard bits * \param[in] len Length of the array of hard bits * \returns The CRC value */ uintXX_t osmo_crcXXgen_compute_bits(const struct osmo_crcXXgen_code *code, const ubit_t *in, int len) { const uintXX_t poly = code->poly; uintXX_t crc = code->init; int i, n = code->bits-1; for (i=0; i<len; i++) { uintXX_t bit = in[i] & 1; crc ^= (bit << n); if (crc & ((uintXX_t)1 << n)) { crc <<= 1; crc ^= poly; } else { crc <<= 1; } crc &= ((uintXX_t)1 << code->bits) - 1; } crc ^= code->remainder; return crc; } /*! Checks the CRC value of a given array of hard-bits * \param[in] code The CRC code description to apply * \param[in] in Array of hard bits * \param[in] len Length of the array of hard bits * \param[in] crc_bits Array of hard bits with the alleged CRC * \returns 0 if CRC matches. 1 in case of error. * * The crc_bits array must have a length of code->len */ int osmo_crcXXgen_check_bits(const struct osmo_crcXXgen_code *code, const ubit_t *in, int len, const ubit_t *crc_bits) { uintXX_t crc; int i; crc = osmo_crcXXgen_compute_bits(code, in, len); for (i=0; i<code->bits; i++) if (crc_bits[i] ^ ((crc >> (code->bits-i-1)) & 1)) return 1; return 0; } /*! Computes and writes the CRC value of a given array of bits * \param[in] code The CRC code description to apply * \param[in] in Array of hard bits * \param[in] len Length of the array of hard bits * \param[in] crc_bits Array of hard bits to write the computed CRC to * * The crc_bits array must have a length of code->len */ void osmo_crcXXgen_set_bits(const struct osmo_crcXXgen_code *code, const ubit_t *in, int len, ubit_t *crc_bits) { uintXX_t crc; int i; crc = osmo_crcXXgen_compute_bits(code, in, len); for (i=0; i<code->bits; i++) crc_bits[i] = ((crc >> (code->bits-i-1)) & 1); } /*! @} */ /* vim: set syntax=c: */