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Diffstat (limited to 'src/core/crcXXgen.c.tpl')
-rw-r--r-- | src/core/crcXXgen.c.tpl | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/src/core/crcXXgen.c.tpl b/src/core/crcXXgen.c.tpl new file mode 100644 index 00000000..154291cc --- /dev/null +++ b/src/core/crcXXgen.c.tpl @@ -0,0 +1,114 @@ +/*! \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. + */ + +/*! \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: */ |