CRC-16 / EN-13757

/* 
 * Model: CRC-16 / EN-13757 (16-bit)
 * Poly: 0x3D65, Init: 0x0000, XorOut: 0xFFFF
 * CRC Table C Source Code & Lookup Table Generator
 */
#include <stdint.h>
#include <stddef.h>

const uint16_t crc_table[256] = {
  0x0000, 0x3D65, 0x7ACA, 0x47AF, 0xF594, 0xC8F1, 0x8F5E, 0xB23B, 
  0xD64D, 0xEB28, 0xAC87, 0x91E2, 0x23D9, 0x1EBC, 0x5913, 0x6476, 
  0x91FF, 0xAC9A, 0xEB35, 0xD650, 0x646B, 0x590E, 0x1EA1, 0x23C4, 
  0x47B2, 0x7AD7, 0x3D78, 0x001D, 0xB226, 0x8F43, 0xC8EC, 0xF589, 
  0x1E9B, 0x23FE, 0x6451, 0x5934, 0xEB0F, 0xD66A, 0x91C5, 0xACA0, 
  0xC8D6, 0xF5B3, 0xB21C, 0x8F79, 0x3D42, 0x0027, 0x4788, 0x7AED, 
  0x8F64, 0xB201, 0xF5AE, 0xC8CB, 0x7AF0, 0x4795, 0x003A, 0x3D5F, 
  0x5929, 0x644C, 0x23E3, 0x1E86, 0xACBD, 0x91D8, 0xD677, 0xEB12, 
  0x3D36, 0x0053, 0x47FC, 0x7A99, 0xC8A2, 0xF5C7, 0xB268, 0x8F0D, 
  0xEB7B, 0xD61E, 0x91B1, 0xACD4, 0x1EEF, 0x238A, 0x6425, 0x5940, 
  0xACC9, 0x91AC, 0xD603, 0xEB66, 0x595D, 0x6438, 0x2397, 0x1EF2, 
  0x7A84, 0x47E1, 0x004E, 0x3D2B, 0x8F10, 0xB275, 0xF5DA, 0xC8BF, 
  0x23AD, 0x1EC8, 0x5967, 0x6402, 0xD639, 0xEB5C, 0xACF3, 0x9196, 
  0xF5E0, 0xC885, 0x8F2A, 0xB24F, 0x0074, 0x3D11, 0x7ABE, 0x47DB, 
  0xB252, 0x8F37, 0xC898, 0xF5FD, 0x47C6, 0x7AA3, 0x3D0C, 0x0069, 
  0x641F, 0x597A, 0x1ED5, 0x23B0, 0x918B, 0xACEE, 0xEB41, 0xD624, 
  0x7A6C, 0x4709, 0x00A6, 0x3DC3, 0x8FF8, 0xB29D, 0xF532, 0xC857, 
  0xAC21, 0x9144, 0xD6EB, 0xEB8E, 0x59B5, 0x64D0, 0x237F, 0x1E1A, 
  0xEB93, 0xD6F6, 0x9159, 0xAC3C, 0x1E07, 0x2362, 0x64CD, 0x59A8, 
  0x3DDE, 0x00BB, 0x4714, 0x7A71, 0xC84A, 0xF52F, 0xB280, 0x8FE5, 
  0x64F7, 0x5992, 0x1E3D, 0x2358, 0x9163, 0xAC06, 0xEBA9, 0xD6CC, 
  0xB2BA, 0x8FDF, 0xC870, 0xF515, 0x472E, 0x7A4B, 0x3DE4, 0x0081, 
  0xF508, 0xC86D, 0x8FC2, 0xB2A7, 0x009C, 0x3DF9, 0x7A56, 0x4733, 
  0x2345, 0x1E20, 0x598F, 0x64EA, 0xD6D1, 0xEBB4, 0xAC1B, 0x917E, 
  0x475A, 0x7A3F, 0x3D90, 0x00F5, 0xB2CE, 0x8FAB, 0xC804, 0xF561, 
  0x9117, 0xAC72, 0xEBDD, 0xD6B8, 0x6483, 0x59E6, 0x1E49, 0x232C, 
  0xD6A5, 0xEBC0, 0xAC6F, 0x910A, 0x2331, 0x1E54, 0x59FB, 0x649E, 
  0x00E8, 0x3D8D, 0x7A22, 0x4747, 0xF57C, 0xC819, 0x8FB6, 0xB2D3, 
  0x59C1, 0x64A4, 0x230B, 0x1E6E, 0xAC55, 0x9130, 0xD69F, 0xEBFA, 
  0x8F8C, 0xB2E9, 0xF546, 0xC823, 0x7A18, 0x477D, 0x00D2, 0x3DB7, 
  0xC83E, 0xF55B, 0xB2F4, 0x8F91, 0x3DAA, 0x00CF, 0x4760, 0x7A05, 
  0x1E73, 0x2316, 0x64B9, 0x59DC, 0xEBE7, 0xD682, 0x912D, 0xAC48
};

uint16_t calculate_crc(const uint8_t *data, size_t length) {
    uint16_t crc = 0x0000;
    for (size_t i = 0; i < length; i++) {
        #if 0
        uint8_t idx = (uint8_t)(crc ^ data[i]);
        crc = (crc >> 8) ^ crc_table[idx];
        #else
        uint8_t idx = (uint8_t)((crc >> 8) ^ data[i]);
        crc = (crc << 8) ^ crc_table[idx];
        #endif
    }
    return crc ^ 0xFFFF;
}