File content as of revision 27:26b0d4560351:

/* SD/MMC File System Library
 * Copyright (c) 2016 Neil Thiessen
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "SDCRC.h"

namespace SDCRC
{

namespace
{
const char m_Crc7Table[] = {
    0x00, 0x09, 0x12, 0x1B, 0x24, 0x2D, 0x36, 0x3F,
    0x48, 0x41, 0x5A, 0x53, 0x6C, 0x65, 0x7E, 0x77,
    0x19, 0x10, 0x0B, 0x02, 0x3D, 0x34, 0x2F, 0x26,
    0x51, 0x58, 0x43, 0x4A, 0x75, 0x7C, 0x67, 0x6E,
    0x32, 0x3B, 0x20, 0x29, 0x16, 0x1F, 0x04, 0x0D,
    0x7A, 0x73, 0x68, 0x61, 0x5E, 0x57, 0x4C, 0x45,
    0x2B, 0x22, 0x39, 0x30, 0x0F, 0x06, 0x1D, 0x14,
    0x63, 0x6A, 0x71, 0x78, 0x47, 0x4E, 0x55, 0x5C,
    0x64, 0x6D, 0x76, 0x7F, 0x40, 0x49, 0x52, 0x5B,
    0x2C, 0x25, 0x3E, 0x37, 0x08, 0x01, 0x1A, 0x13,
    0x7D, 0x74, 0x6F, 0x66, 0x59, 0x50, 0x4B, 0x42,
    0x35, 0x3C, 0x27, 0x2E, 0x11, 0x18, 0x03, 0x0A,
    0x56, 0x5F, 0x44, 0x4D, 0x72, 0x7B, 0x60, 0x69,
    0x1E, 0x17, 0x0C, 0x05, 0x3A, 0x33, 0x28, 0x21,
    0x4F, 0x46, 0x5D, 0x54, 0x6B, 0x62, 0x79, 0x70,
    0x07, 0x0E, 0x15, 0x1C, 0x23, 0x2A, 0x31, 0x38,
    0x41, 0x48, 0x53, 0x5A, 0x65, 0x6C, 0x77, 0x7E,
    0x09, 0x00, 0x1B, 0x12, 0x2D, 0x24, 0x3F, 0x36,
    0x58, 0x51, 0x4A, 0x43, 0x7C, 0x75, 0x6E, 0x67,
    0x10, 0x19, 0x02, 0x0B, 0x34, 0x3D, 0x26, 0x2F,
    0x73, 0x7A, 0x61, 0x68, 0x57, 0x5E, 0x45, 0x4C,
    0x3B, 0x32, 0x29, 0x20, 0x1F, 0x16, 0x0D, 0x04,
    0x6A, 0x63, 0x78, 0x71, 0x4E, 0x47, 0x5C, 0x55,
    0x22, 0x2B, 0x30, 0x39, 0x06, 0x0F, 0x14, 0x1D,
    0x25, 0x2C, 0x37, 0x3E, 0x01, 0x08, 0x13, 0x1A,
    0x6D, 0x64, 0x7F, 0x76, 0x49, 0x40, 0x5B, 0x52,
    0x3C, 0x35, 0x2E, 0x27, 0x18, 0x11, 0x0A, 0x03,
    0x74, 0x7D, 0x66, 0x6F, 0x50, 0x59, 0x42, 0x4B,
    0x17, 0x1E, 0x05, 0x0C, 0x33, 0x3A, 0x21, 0x28,
    0x5F, 0x56, 0x4D, 0x44, 0x7B, 0x72, 0x69, 0x60,
    0x0E, 0x07, 0x1C, 0x15, 0x2A, 0x23, 0x38, 0x31,
    0x46, 0x4F, 0x54, 0x5D, 0x62, 0x6B, 0x70, 0x79
};

const unsigned short m_Crc16Table[256] = {
    0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
    0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
    0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
    0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
    0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
    0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
    0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
    0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
    0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
    0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
    0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
    0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
    0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
    0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
    0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
    0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
    0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
    0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
    0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
    0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
    0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
    0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
    0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
    0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
    0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
    0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
    0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
    0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
    0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
    0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
    0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
    0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
};
}

char crc7(const char* data, int length)
{
    //Calculate the CRC7 checksum for the specified data block
    char crc = 0;
    for (int i = 0; i < length; i++) {
        crc = m_Crc7Table[(crc << 1) ^ data[i]];
    }

    //Return the calculated checksum
    return crc;
}

unsigned short crc16(const char* data, int length)
{
    //Calculate the CRC16 checksum for the specified data block
    unsigned short crc = 0;
    for (int i = 0; i < length; i++) {
        crc = (crc << 8) ^ m_Crc16Table[((crc >> 8) ^ data[i]) & 0x00FF];
    }

    //Return the calculated checksum
    return crc;
}

}