/*----------------------------------------------------------------------------
 * Tencent is pleased to support the open source community by making TencentOS
 * available.
 *
 * Copyright (C) 2019 THL A29 Limited, a Tencent company. All rights reserved.
 * If you have downloaded a copy of the TencentOS binary from Tencent, please
 * note that the TencentOS binary is licensed under the BSD 3-Clause License.
 *
 * If you have downloaded a copy of the TencentOS source code from Tencent,
 * please note that TencentOS source code is licensed under the BSD 3-Clause
 * License, except for the third-party components listed below which are
 * subject to different license terms. Your integration of TencentOS into your
 * own projects may require compliance with the BSD 3-Clause License, as well
 * as the other licenses applicable to the third-party components included
 * within TencentOS.
 *---------------------------------------------------------------------------*/

#include "crc8.h"

uint8_t crc8(uint8_t crc, uint8_t *buf, int nbyte)
{
    int i;

#define POLY            0x31
#define WIDTH           8
#define TOP_BIT         0x80

    while (nbyte--) {
        crc ^= *buf++;
        for (i = 0; i < WIDTH; ++i) {
            if (crc & TOP_BIT) {
                crc = (crc << 1) ^ POLY;
            } else {
                crc <<= 1;
            }
        }
        crc &= 0xFF;
    }

    return crc;
}