#include <stdbool.h>

static unsigned short table[256] =
{
    0x0000, 0x1c06, 0x340a, 0x280c, 0x6814, 0x7412, 0x5c1e, 0x4018,
    0xdc2e, 0xc028, 0xe824, 0xf422, 0xb43a, 0xa83c, 0x8030, 0x9c36,
    0xb45a, 0xa85c, 0x8050, 0x9c56, 0xdc4e, 0xc048, 0xe844, 0xf442,
    0x6874, 0x7472, 0x5c7e, 0x4078, 0x0060, 0x1c66, 0x346a, 0x286c,
    0x68b4, 0x74b2, 0x5cbe, 0x40b8, 0x00a0, 0x1ca6, 0x34aa, 0x28ac,
    0xb49a, 0xa89c, 0x8090, 0x9c96, 0xdc8e, 0xc088, 0xe884, 0xf482,
    0xdcee, 0xc0e8, 0xe8e4, 0xf4e2, 0xb4fa, 0xa8fc, 0x80f0, 0x9cf6,
    0x00c0, 0x1cc6, 0x34ca, 0x28cc, 0x68d4, 0x74d2, 0x5cde, 0x40d8,
    0xdd6e, 0xc168, 0xe964, 0xf562, 0xb57a, 0xa97c, 0x8170, 0x9d76,
    0x0140, 0x1d46, 0x354a, 0x294c, 0x6954, 0x7552, 0x5d5e, 0x4158,
    0x6934, 0x7532, 0x5d3e, 0x4138, 0x0120, 0x1d26, 0x352a, 0x292c,
    0xb51a, 0xa91c, 0x8110, 0x9d16, 0xdd0e, 0xc108, 0xe904, 0xf502,
    0xb5da, 0xa9dc, 0x81d0, 0x9dd6, 0xddce, 0xc1c8, 0xe9c4, 0xf5c2,
    0x69f4, 0x75f2, 0x5dfe, 0x41f8, 0x01e0, 0x1de6, 0x35ea, 0x29ec,
    0x0180, 0x1d86, 0x358a, 0x298c, 0x6994, 0x7592, 0x5d9e, 0x4198,
    0xddae, 0xc1a8, 0xe9a4, 0xf5a2, 0xb5ba, 0xa9bc, 0x81b0, 0x9db6,
    0xb6da, 0xaadc, 0x82d0, 0x9ed6, 0xdece, 0xc2c8, 0xeac4, 0xf6c2,
    0x6af4, 0x76f2, 0x5efe, 0x42f8, 0x02e0, 0x1ee6, 0x36ea, 0x2aec,
    0x0280, 0x1e86, 0x368a, 0x2a8c, 0x6a94, 0x7692, 0x5e9e, 0x4298,
    0xdeae, 0xc2a8, 0xeaa4, 0xf6a2, 0xb6ba, 0xaabc, 0x82b0, 0x9eb6,
    0xde6e, 0xc268, 0xea64, 0xf662, 0xb67a, 0xaa7c, 0x8270, 0x9e76,
    0x0240, 0x1e46, 0x364a, 0x2a4c, 0x6a54, 0x7652, 0x5e5e, 0x4258,
    0x6a34, 0x7632, 0x5e3e, 0x4238, 0x0220, 0x1e26, 0x362a, 0x2a2c,
    0xb61a, 0xaa1c, 0x8210, 0x9e16, 0xde0e, 0xc208, 0xea04, 0xf602,
    0x6bb4, 0x77b2, 0x5fbe, 0x43b8, 0x03a0, 0x1fa6, 0x37aa, 0x2bac,
    0xb79a, 0xab9c, 0x8390, 0x9f96, 0xdf8e, 0xc388, 0xeb84, 0xf782,
    0xdfee, 0xc3e8, 0xebe4, 0xf7e2, 0xb7fa, 0xabfc, 0x83f0, 0x9ff6,
    0x03c0, 0x1fc6, 0x37ca, 0x2bcc, 0x6bd4, 0x77d2, 0x5fde, 0x43d8,
    0x0300, 0x1f06, 0x370a, 0x2b0c, 0x6b14, 0x7712, 0x5f1e, 0x4318,
    0xdf2e, 0xc328, 0xeb24, 0xf722, 0xb73a, 0xab3c, 0x8330, 0x9f36,
    0xb75a, 0xab5c, 0x8350, 0x9f56, 0xdf4e, 0xc348, 0xeb44, 0xf742,
    0x6b74, 0x7772, 0x5f7e, 0x4378, 0x0360, 0x1f66, 0x376a, 0x2b6c
};

short crc12(unsigned char const *data, int length)
{
    unsigned short remainder = 0;
    unsigned char index;
    int i;

    for(i = 0; i < length; ++i)
    {
        index = remainder >> 4;
        remainder <<= 8;
        remainder |= data[i];
        remainder ^= table[index];
    }

    return remainder & 0x0fff;
}

bool crc12_check(unsigned char const *data, int length)
{
    return !crc12(data, length);
}