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https://github.com/aaru-dps/Aaru.Checksums.Native.git
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140 lines
4.3 KiB
C
140 lines
4.3 KiB
C
/*
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* This file is part of the Aaru Data Preservation Suite.
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* Copyright (c) 2019-2023 Natalia Portillo.
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*
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* This library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 2.1 of the
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* License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include "library.h"
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#include "crc16.h"
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/**
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* @brief Initializes the CRC-16 checksum algorithm with the IBM polynomial.
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*
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* This function initializes the state variables required for the CRC-16
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* checksum algorithm using the IBM polynomial. It prepares the algorithm
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* to calculate the checksum for a new data set.
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*
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* @return Pointer to a structure containing the checksum state.
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*/
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AARU_EXPORT crc16_ctx* AARU_CALL crc16_init(void)
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{
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crc16_ctx* ctx = (crc16_ctx*)malloc(sizeof(crc16_ctx));
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if(!ctx) return NULL;
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ctx->crc = 0x0000;
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return ctx;
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}
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/**
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* @brief Updates the CRC-16 checksum with new data.
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*
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* This function updates the CRC-16 checksum.
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* The checksum is updated for the given data by using the IBM polynomial.
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* The algorithm continues the checksum calculation from the previous state,
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* so it can be used to update the checksum with new data as it is read.
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*
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* @param ctx Pointer to the CRC-16 context structure.
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* @param data Pointer to the input data buffer.
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* @param len The length of the input data buffer.
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*
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* @returns 0 on success, -1 on error.
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*/
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AARU_EXPORT int AARU_CALL crc16_update(crc16_ctx* ctx, const uint8_t* data, uint32_t len)
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{
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// Unroll according to Intel slicing by uint8_t
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// http://www.intel.com/technology/comms/perfnet/download/CRC_generators.pdf
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// http://sourceforge.net/projects/slicing-by-8/
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if(!ctx || !data) return -1;
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uint16_t crc;
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const uint32_t* current;
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const uint8_t* current_char = (const uint8_t*)data;
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const size_t unroll = 4;
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const size_t bytes_at_once = 8 * unroll;
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uintptr_t unaligned_length = (4 - (((uintptr_t)current_char) & 3)) & 3;
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crc = ctx->crc;
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while((len != 0) && (unaligned_length != 0))
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{
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crc = (crc >> 8) ^ crc16_table[0][(crc & 0xFF) ^ *current_char++];
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len--;
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unaligned_length--;
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}
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current = (const uint32_t*)current_char;
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while(len >= bytes_at_once)
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{
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size_t unrolling;
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for(unrolling = 0; unrolling < unroll; unrolling++)
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{
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uint32_t one = *current++ ^ crc;
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uint32_t two = *current++;
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// TODO: Big endian!
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crc = crc16_table[0][(two >> 24) & 0xFF] ^ crc16_table[1][(two >> 16) & 0xFF] ^
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crc16_table[2][(two >> 8) & 0xFF] ^ crc16_table[3][two & 0xFF] ^ crc16_table[4][(one >> 24) & 0xFF] ^
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crc16_table[5][(one >> 16) & 0xFF] ^ crc16_table[6][(one >> 8) & 0xFF] ^ crc16_table[7][one & 0xFF];
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}
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len -= bytes_at_once;
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}
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current_char = (const uint8_t*)current;
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while(len-- != 0) crc = (crc >> 8) ^ crc16_table[0][(crc & 0xFF) ^ *current_char++];
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ctx->crc = crc;
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return 0;
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}
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/**
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* @brief Finalizes the calculation of the CRC-16 checksum.
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*
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* This function finalizes the calculation of the CRC-16 checksum and returns
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* its value.
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*
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* @param[in] ctx Pointer to the CRC-16 context structure.
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* @param[out] checksum Pointer to a 16-bit unsigned integer to store the checksum value.
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*
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* @returns 0 on success, -1 on error.
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*/
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AARU_EXPORT int AARU_CALL crc16_final(crc16_ctx* ctx, uint16_t* crc)
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{
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if(!ctx) return -1;
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*crc = ctx->crc;
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return 0;
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}
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/**
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* @brief Frees the resources allocated for the CRC-16 checksum context.
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*
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* This function should be called to release the memory used by the CRC-16 checksum
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* context structure after it is no longer needed.
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*
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* @param ctx The CRC-16 checksum context structure, to be freed.
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*/
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AARU_EXPORT void AARU_CALL crc16_free(crc16_ctx* ctx)
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{
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if(ctx) free(ctx);
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} |