// -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; st-rulers: [132] -*-
// vim: ts=4 sw=4 ft=c++ et

#include "crc_16.h"
#include "xnif_slice.h"

static const uint16_t crc_16_ccitt_table[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};

uint16_t
crc_16_ccitt_init(uint16_t seed)
{
    return seed;
}

uint16_t
crc_16_ccitt_update(uint16_t ctx, const unsigned char *buf, size_t len)
{
    uint16_t result = ctx;
    int tblIndx = 0;
    size_t size = len;

    while (size--) {
        tblIndx = ((result >> 8) ^ *(char *)buf++) & 0x00ff;
        result = (result << 8) ^ crc_16_ccitt_table[tblIndx];
    }

    return result;
}

uint16_t
crc_16_ccitt_final(uint16_t ctx)
{
    return ctx;
}

/* NIF Functions */

static int crc_nif_crc_16_ccitt_2_work(ErlNifEnv *env, xnif_slice_t *slice, int *phasep, size_t *offsetp, size_t reductions);
static ERL_NIF_TERM crc_nif_crc_16_ccitt_2_done(ErlNifEnv *env, xnif_slice_t *slice);

static xnif_slice_func_t crc_nif_crc_16_ccitt_2_func = {
    crc_nif_crc_16_ccitt_2_work, crc_nif_crc_16_ccitt_2_done, NULL, NULL,
};

ERL_NIF_TERM
crc_nif_crc_16_ccitt_2(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    unsigned int seed;
    ErlNifBinary input;

    if (argc != 2 || !enif_get_uint(env, argv[0], &seed) || seed > 0xffff || !enif_inspect_binary(env, argv[1], &input)) {
        return enif_make_badarg(env);
    }

    if (input.size <= XNIF_SLICE_MAX_PER_SLICE) {
        uint16_t crc;
        crc = crc_16_ccitt((uint16_t)seed, input.data, input.size);
        return enif_make_uint(env, crc);
    }

    xnif_slice_t *slice = xnif_slice_create("crc_16_ccitt", &crc_nif_crc_16_ccitt_2_func, 0, input.size);
    if (slice == NULL) {
        return enif_make_badarg(env);
    }
    uint16_t ctx = crc_16_ccitt_init((uint16_t)seed);
    ERL_NIF_TERM newargv[2];
    newargv[0] = enif_make_uint(env, ctx);
    newargv[1] = argv[0];
    return xnif_slice_schedule(env, slice, 2, newargv);
}

static int
crc_nif_crc_16_ccitt_2_work(ErlNifEnv *env, xnif_slice_t *slice, int *phasep, size_t *offsetp, size_t reductions)
{
    size_t offset = *offsetp;
    uint16_t ctx;
    ErlNifBinary input;
    if (slice->argc != 2 || !enif_get_uint(env, slice->argv[0], (unsigned int *)&ctx) ||
        !enif_inspect_binary(env, slice->argv[1], &input)) {
        return -1;
    }
    ctx = crc_16_ccitt_update(ctx, input.data + offset, reductions);
    slice->argv[0] = enif_make_uint(env, ctx);
    *offsetp = offset + reductions;
    return 0;
}

static ERL_NIF_TERM
crc_nif_crc_16_ccitt_2_done(ErlNifEnv *env, xnif_slice_t *slice)
{
    uint16_t ctx;
    if (slice->argc != 2 || !enif_get_uint(env, slice->argv[0], (unsigned int *)&ctx)) {
        return enif_make_badarg(env);
    }
    return enif_make_uint(env, crc_16_ccitt_final(ctx));
}

ERL_NIF_TERM
crc_nif_crc_16_ccitt_init_1(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    unsigned int seed;

    if (argc != 1 || !enif_get_uint(env, argv[0], &seed) || seed > 0xff) {
        return enif_make_badarg(env);
    }

    uint16_t ctx = crc_16_ccitt_init((uint16_t)seed);
    return enif_make_uint(env, ctx);
}

static int crc_nif_crc_16_ccitt_update_2_work(ErlNifEnv *env, xnif_slice_t *slice, int *phasep, size_t *offsetp, size_t reductions);
static ERL_NIF_TERM crc_nif_crc_16_ccitt_update_2_done(ErlNifEnv *env, xnif_slice_t *slice);

static xnif_slice_func_t crc_nif_crc_16_ccitt_update_2_func = {
    crc_nif_crc_16_ccitt_update_2_work, crc_nif_crc_16_ccitt_update_2_done, NULL, NULL,
};

ERL_NIF_TERM
crc_nif_crc_16_ccitt_update_2(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    unsigned int ctx;
    ErlNifBinary input;

    if (argc != 2 || !enif_get_uint(env, argv[0], &ctx) || ctx > 0xffff || !enif_inspect_binary(env, argv[1], &input)) {
        return enif_make_badarg(env);
    }

    if (input.size <= XNIF_SLICE_MAX_PER_SLICE) {
        ctx = crc_16_ccitt_update((uint16_t)ctx, input.data, input.size);
        return enif_make_uint(env, ctx);
    }

    xnif_slice_t *slice = xnif_slice_create("crc_16_ccitt_update", &crc_nif_crc_16_ccitt_update_2_func, 0, input.size);
    if (slice == NULL) {
        return enif_make_badarg(env);
    }
    ERL_NIF_TERM newargv[2];
    newargv[0] = argv[0];
    newargv[1] = argv[1];
    return xnif_slice_schedule(env, slice, 2, newargv);
}

static int
crc_nif_crc_16_ccitt_update_2_work(ErlNifEnv *env, xnif_slice_t *slice, int *phasep, size_t *offsetp, size_t reductions)
{
    size_t offset = *offsetp;
    uint16_t ctx;
    ErlNifBinary input;
    if (slice->argc != 2 || !enif_get_uint(env, slice->argv[0], (unsigned int *)&ctx) ||
        !enif_inspect_binary(env, slice->argv[1], &input)) {
        return -1;
    }
    ctx = crc_16_ccitt_update(ctx, input.data + offset, reductions);
    slice->argv[0] = enif_make_uint(env, ctx);
    *offsetp = offset + reductions;
    return 0;
}

static ERL_NIF_TERM
crc_nif_crc_16_ccitt_update_2_done(ErlNifEnv *env, xnif_slice_t *slice)
{
    uint16_t ctx;
    if (slice->argc != 2 || !enif_get_uint(env, slice->argv[0], (unsigned int *)&ctx)) {
        return enif_make_badarg(env);
    }
    return enif_make_uint(env, ctx);
}

ERL_NIF_TERM
crc_nif_crc_16_ccitt_final_1(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    unsigned int ctx;

    if (argc != 1 || !enif_get_uint(env, argv[0], &ctx) || ctx > 0xffff) {
        return enif_make_badarg(env);
    }

    uint16_t crc = crc_16_ccitt_final((uint16_t)ctx);
    return enif_make_uint(env, crc);
}